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Code Meaning: P155B-00
The Nissan P155B-00 code signals a stuck-closed coolant bypass valve. While it may seem minor, it carries the real risk of engine overheating and catastrophic damage. The good news: the repair is well-understood, parts are readily available, and a competent shop or DIYer can fix it in a few hours.
If your Nissan has triggered this code, don’t ignore it. Diagnose promptly, replace the faulty valve, and get back on the road with confidence.
Disclaimer: This article is for informational purposes only. Always consult a professional mechanic or your vehicle’s service manual for model-specific procedures. Vehicle repairs should be performed by qualified individuals following safety guidelines.
The Nissan fault code P155B-00 indicates a range/performance issue with the Variable Geometry Turbocharger (VGT) Actuator. Specifically, the engine control module (ECM) detects that the turbocharger vanes are not moving to the commanded position or are moving too slowly. Limp Mode: Significant loss of power or RPM restriction. Hesitation: Poor throttle response during acceleration.
Warning Lights: "Check Engine" or "Drivetrain Malfunction" alerts. Smoke: Excessive black smoke from the exhaust under load. Common Causes
Soot Buildup: Carbon deposits jamming the internal turbo vanes (most common in diesels).
Faulty Actuator: Internal electronic failure of the turbo control motor.
Wiring Issues: Corroded or frayed wires in the harness connecting the actuator to the ECM.
Vacuum Leaks: (On older vacuum-actuated models) cracked or disconnected vacuum lines. Troubleshooting & Fixes 1. Visual & Manual Inspection
Check Linkage: Inspect the rod between the actuator and the turbo. Ensure it moves freely and isn't bent.
Inspect Wiring: Look for "green corrosion" in the actuator plug or melted insulation near hot exhaust parts. 2. Basic Cleaning
Turbo Cleaning: In some cases, specialized "VGT cleaner" can be used to break down soot without removing the turbo.
Clear Codes: Use an OBD-II scanner to clear the code and see if it returns immediately after a test drive.
The code P155B-00 on a Nissan is an OBD-II diagnostic trouble code that typically refers to an issue with the variable geometry turbocharger (VGT) control system, specifically a calibration or "initialization" error with the VGT actuator.
While this code is often confused with more common O2 sensor codes like P0155 or P015B (which deal with the oxygen sensor heater circuit or delayed response times), the P155B-00 designation is specifically tied to turbocharger management in modern Nissan diesel or turbo-gasoline engines. Meaning of P155B-00
The suffix -00 indicates there are no additional sub-types defined for the fault, essentially serving as a general "fault detected" flag. In the context of a Nissan, this code usually triggers when the Engine Control Module (ECM) detects that the turbocharger actuator has not been correctly initialized or has lost its learned position. This means the engine's "brain" is unsure how to properly adjust the turbo vanes to provide the right amount of boost. Common Symptoms When this code is stored, you will likely notice:
Reduced Engine Power: The vehicle may enter a "limp home" mode to protect the turbo from over-boosting or under-boosting.
Check Engine Light: The Malfunction Indicator Lamp (MIL) will illuminate.
Poor Acceleration: Because the turbo vanes aren't adjusting correctly, the engine lacks responsiveness at different RPM ranges.
Increased Fuel Consumption: Inefficient boost levels force the engine to work harder. Potential Causes
Actuator Initialization Failure: This is the most common cause, often occurring after a battery replacement, an ECM update, or a turbocharger repair where the actuator was not properly "re-learned" using a scan tool.
Stuck Turbo Vanes: Carbon buildup inside the turbocharger can physically prevent the vanes from moving, causing the actuator to fail its startup self-test.
Faulty VGT Actuator: The electronic motor inside the actuator may be failing or have internal electrical issues.
Wiring or Connector Issues: Corrosion or damage to the wiring harness between the ECM and the turbo actuator. Diagnostic Steps
Perform a Re-learn Procedure: Using a professional-grade scan tool, attempt to perform the "VGT Actuator Initialization" or "Turbo Re-learn" process. This is often the quickest fix if the hardware is still healthy.
Inspect Wiring: Check the electrical connector at the turbocharger for signs of moisture, heat damage, or loose pins.
Check Vane Movement: Ensure the turbocharger linkage moves freely and isn't seized due to soot buildup.
Because this code specifically relates to precise turbocharger calibration, ignoring it can lead to more expensive repairs, such as complete turbocharger failure or damage to emissions components like the catalytic converter.
The Nissan fault code specifically refers to a malfunction in the Battery Current Sensor
. This sensor monitors the amperage produced by the alternator to maintain the battery's charge and oversees the current flow for various vehicle components. JustAnswer Understanding P155B-00 Definition : Battery Current Sensor Circuit Malfunction. Primary Function
: The sensor tracks how much current is going into or out of the battery. The Engine Control Module (ECM) uses this data to manage the alternator's output and optimize fuel efficiency through the smart charging system. Illuminated Check Engine Light (MIL). Charging system warnings.
Potential slight fluctuations in engine RPM if the alternator load switches erratically. JustAnswer Common Causes Defective Sensor
: A failed battery current sensor unit located on the negative battery terminal. Wiring Issues
: Corroded, loose, or damaged wiring/connectors at the sensor. Battery Condition
: An aging battery that requires excessive amperage to charge may sometimes trigger sensor-related logic codes. JustAnswer Diagnostic Steps Visual Inspection
: Check the negative battery terminal for loose connections or corrosion on the sensor and its harness. Battery Test
: Ensure the battery itself is healthy and holding a charge (typically between 12.0 - 15.5 V Code Reset
: In some cases, resetting the code is recommended to see if it was a "soft" failure before replacing expensive parts. Sensor Replacement
: If the wiring and battery are confirmed good, the sensor assembly (often integrated into the battery cable) usually needs replacement. YarikSteel.RU or a specific part number for the sensor? NISSAN B13 and N14 Official Factory Workshop Manual Vol 1
The diagnostic trouble code (DTC) P155B-00 in Nissan vehicles is a manufacturer-specific code primarily associated with the variable geometry turbocharger (VGT) control system. Specifically, it indicates a performance issue or a "rationality" fault with the turbocharger boost control actuator. Technical Overview
In modern Nissan diesel engines (such as the 2.3L dCi found in the Navara or Terra), the VGT system uses an electronic actuator to adjust the vanes inside the turbocharger. This adjustment regulates the amount of boost pressure delivered to the engine based on load and speed. When the Engine Control Module (ECM) detects that the actual position of these vanes does not match the commanded position, it triggers the P155B-00 code. Common Symptoms When this code is stored, drivers typically experience:
Limp Mode: The vehicle may significantly reduce power to protect the engine.
Check Engine Light: The Malfunction Indicator Lamp (MIL) will illuminate. nissan p155b-00
Poor Acceleration: A noticeable "lag" or lack of power under load.
Hissing or Whining: Unusual sounds from the turbocharger area. Root Causes
Carbon Buildup: The most frequent cause is soot and carbon accumulation inside the turbocharger. This "sooting" causes the internal vanes to stick, preventing the actuator from moving them freely.
Actuator Failure: The electronic motor or the internal gears of the turbocharger actuator may wear out or fail due to heat and vibration.
Wiring Issues: Corroded connectors or broken wires between the ECM and the turbocharger actuator can disrupt the signal.
Boost Leaks: While less common for this specific code, a significant leak in the intercooler pipes can sometimes cause a rationality error in the boost control system. Diagnostic and Repair Path
To resolve a P155B-00 code, technicians generally follow a tiered approach:
Visual Inspection: Checking the linkage between the actuator and the turbocharger. If the arm is stuck and cannot be moved by hand (with the actuator disconnected), the turbo vanes are physically seized.
Actuator Test: Using a diagnostic scan tool to perform a "Component Test" or "Active Test" to command the actuator to move through its full range.
Cleaning vs. Replacement: If carbon buildup is the culprit, some specialized cleaning services (like hydrogen cleaning or chemical soaking) may free the vanes. However, if the internal components are damaged or the electronic actuator has failed, the standard repair is the replacement of the entire turbocharger assembly, as the actuator and turbo are often calibrated as a single unit.
Nissan P155B-00: Understanding and Troubleshooting the Throttle Control System Fault
If you're a Nissan owner, you've likely encountered the frustrating experience of receiving a fault code. One such code that's been reported by several Nissan enthusiasts is the P155B-00. In this post, we'll explore the meaning, causes, symptoms, and potential fixes for this throttle control system fault.
What does P155B-00 mean?
The P155B-00 code refers to a fault in the throttle control system, specifically related to the electronic throttle control (ETC) system. The "00" at the end indicates that it's a generic OBD-II code.
Symptoms:
Vehicles experiencing the P155B-00 code may exhibit one or more of the following symptoms:
Causes:
The P155B-00 code can be triggered by various factors, including:
Troubleshooting steps:
If you've encountered the P155B-00 code, try the following steps:
Fixes and repairs:
Based on the underlying cause, potential fixes may include:
Conclusion
The P155B-00 code can be a challenging issue to diagnose and repair, but by understanding the possible causes and symptoms, you can take the first steps towards resolving the problem. If you're not experienced with DIY repairs, it's always best to consult a professional mechanic to ensure a proper and safe repair.
Share your experiences!
Have you encountered the P155B-00 code in your Nissan? Share your experiences, symptoms, and repair stories in the comments below. This can help others who may be facing similar issues.
Understanding the Nissan P155B-00 Error Code: A Deep Dive If you’ve recently scanned your Nissan and were greeted by the diagnostic trouble code (DTC) P155B-00, you might be feeling a bit stumped. Unlike common codes for spark plugs or gas caps, this one is specific and can affect how your car manages its electrical power.
In this post, we’ll break down what P155B-00 means, why it happens, and how to get your Nissan back to 100%. What is P155B-00?
The code P155B-00 typically points to an issue within the Energy Management Control system. In modern Nissan vehicles, the Energy Management system is responsible for monitoring how much electricity is being pulled from and sent to your battery to ensure peak efficiency.
While "P155B" is the main code, the "-00" suffix is a sub-type identifier indicating that no further specific subtype information is available—it's a general circuit or system fault. Common Symptoms When this code is triggered, you might notice: A Check Engine Light (MIL): The most obvious sign.
Charging Issues: The vehicle may not manage battery charging correctly.
Auto Start-Stop Failure: If your Nissan has the auto start-stop feature, it may be disabled because the system can't verify the battery's health.
Weak Starts: You might feel the engine struggling slightly more than usual during ignition. Potential Causes
Multiple components work together in the Energy Management system. P155B-00 is usually caused by:
Faulty Battery Current Sensor: This sensor sits on the negative battery terminal and measures the current flow. If it fails or sends a "low input" signal, the ECM loses its ability to manage energy.
Wiring or Connector Issues: Corroded or loose wires between the battery sensor and the Engine Control Module (ECM) or Intelligent Power Distribution Module (IPDM) can trigger this fault.
Weak or Dying Battery: Sometimes, a battery that can no longer hold a proper charge confuses the sensor, leading to a "ghost" code.
Alternator Problems: If the generator is under-performing, the energy management system may flag a circuit error. How to Fix It
Before you start replacing expensive parts, follow these diagnostic steps: 1. Check Battery Health
Ensure your battery is providing at least 11V at idle. Many electrical codes in Nissans are simply the result of a battery nearing the end of its life. 2. Inspect the Battery Current Sensor
Look at the sensor attached to your negative battery cable. Are the connectors tight? Is there any visible corrosion? Cleaning the terminals with electrical contact cleaner can sometimes resolve the issue. 3. Diagnostic Prioritization
If you also see codes P155E or P155F, Nissan service manuals recommend fixing those first, as they are often the "root" cause that triggers the P155B-00 secondary fault. 4. Clear the Code and Test
Use an OBD-II scanner to clear the code. Start the engine and let it idle for at least 20 seconds to see if the code returns immediately. If it does, the current sensor likely needs replacement. Summary Table What to Check Battery Voltage should be >11V at idle. Harness/Wiring Look for frayed wires near the battery terminals. Connectors Ensure the 2-pin or 3-pin sensor plug is seated fully. Alternator Check for steady output under load.
Do you have other error codes appearing alongside P155B-00, or did this code appear right after a battery replacement? What is mal function error after scanning?
Nissan fault code P155B-00 (often seen in models like the Nissan Navara, Frontier, or Titan) indicates a performance issue with the Battery Current Sensor
. This sensor is a small plastic component that surrounds the negative battery cable to monitor how much current is flowing in and out of the battery. 1. Meaning of Code P155B-00
: The Engine Control Module (ECM) has detected that the battery current sensor is providing an out-of-range or improbable signal.
: This affects the vehicle's "smart" charging system, which adjusts the alternator's output based on battery demand to improve fuel efficiency. Common Symptoms Check Engine Light is illuminated.
Potential issues with the Auto Start/Stop system (if equipped). Unusual battery charging behavior (fluctuating voltage). 2. Potential Causes
The Nissan fault code typically relates to the Battery Heater Relay Circuit Overview
. This code is most commonly found in Nissan's electrified or hybrid vehicles, such as the Nissan Leaf Nissan Rogue Hybrid
, which use a battery heater to maintain optimal temperatures for the high-voltage battery pack in cold weather. usa.nissannews.com
The "-00" suffix is a sub-type identifier indicating no specific failure information is available, meaning the system has detected a general malfunction within that specific circuit. Potential Causes Faulty Battery Heater Relay
: The most common culprit is a mechanical or electrical failure of the relay itself. Wiring Issues
: Open or shorted circuits in the wiring harness connecting the Engine Control Module (ECM) to the battery heater relay. Blown Fuse
: A blown fuse protecting the heater circuit can prevent power from reaching the heater, triggering the code. Low 12V Battery Voltage
: In many Nissan models, a weak 12V auxiliary battery can cause various communication and relay codes to trigger erroneously. Common Symptoms Check Engine Light (MIL)
: The primary indicator that a fault has been stored in the ECM. Reduced EV Range/Efficiency
: In cold climates, the high-voltage battery may not reach optimal operating temperature, leading to lower efficiency and reduced regenerative braking. Charging Issues
: Some models may restrict fast charging (DC Quick Charge) if the battery heater is non-functional in freezing temperatures. CarParts.com Recommended Troubleshooting Steps Check 12V Battery
: Ensure your auxiliary 12V battery is fully charged and healthy. A simple battery swap or charge often clears "phantom" relay codes. Inspect Fuses
: Locate the IPDM (Intelligent Power Distribution Module) or fuse box and check for any blown fuses related to the battery heater or "BATT HEATER". Test the Relay
: If you have access to the battery heater relay, test it for continuity or swap it with a known good relay of the same type to see if the code clears. Professional Diagnosis
: Because this involves the high-voltage system in hybrids/EVs, it is recommended to have a technician use a Nissan CONSULT diagnostic tool
to perform a circuit test and verify if the relay is receiving the correct signal from the ECM. for a specific Nissan model? 2026 Nissan LEAF Press Kit
The error code glared from the diagnostic tablet: P155B-00 – Battery Current Sensor Circuit Range/Performance.
To most people, it was a cryptic string of letters and numbers. To Mira, it was a death sentence.
She leaned against the cold hood of her Nissan Leaf, the electric-blue paint dulled by three winters of grime. This wasn’t just a car. It was the last tangible piece of her late husband, Leo—a man who believed electricity wasn’t just for gadgets, but for second chances. He’d bought the Leaf used, a salvage title from a flood in Florida, and spent two years resurrecting it. “The heart is fine,” he used to say, tapping the battery pack. “It just needs someone to listen to it.”
Now, the heart was lying.
“P155B-00,” she whispered, the words fogging in the cold air. Leo’s service manual, dog-eared and coffee-stained, lay open on the passenger seat. She’d traced the diagnostic tree three times. Check the wiring harness. Inspect the battery current sensor. Measure voltage drop. Everything pointed to a single, tiny component: a hall-effect sensor clamped around the high-voltage cable leading to the main battery.
Without it, the car’s computer had no idea how much energy was flowing. It would default to a paranoid limp mode, then shut down entirely. The range had already dropped from eighty miles to twenty. Last week, it had stranded her on the hill leading to her daughter’s school.
Mira didn’t have the money for a new sensor. The dealership quoted seven hundred dollars—just for the part. A used one from a junkyard would be a gamble. Leo would have laughed at both options. He’d have opened the hood, rolled up his sleeves, and built a workaround.
“Okay, Leo,” she said, zipping her coat. “Let’s listen.”
She disconnected the twelve-volt battery first—safety. Then she unbolted the orange high-voltage service plug and waited the agonizing ten minutes for the capacitors to discharge. The sensor sat near the rear of the battery case, a black plastic ring with three tiny wires: ground, five-volt reference, and signal.
With a multimeter, she probed the signal wire while a friend revved the Leaf’s heater to draw current. The voltage should have swept smoothly between 0.5 and 4.5 volts. Instead, it twitched erratically, then flatlined.
The sensor was lying.
Mira removed it and brought it inside to her kitchen table, now a makeshift electronics lab. Under a magnifying lamp, she saw the problem: a cracked solder joint on the internal circuit board. The flood damage from years ago had finally crept in, corroding the lead-free solder into a gray crust.
Leo had taught her to solder when they rebuilt a vintage stereo. “Flux is your friend,” he’d said. “And patience is the only tool you can’t buy.”
She found his old soldering iron, the tip blackened but still hot. She scraped away the corrosion, applied a dab of flux, and reheated the joint until it flowed like a silver tear. Then she sealed the sensor housing with marine-grade epoxy—Leo’s favorite waterproofing trick.
At midnight, she reinstalled the sensor. She reconnected the twelve-volt battery, then the high-voltage plug. The Leaf’s dash lit up like a sleepy blue dawn. She plugged in the diagnostic tablet, cleared the code, and held her breath.
The car hummed. The battery indicator showed a steady state of charge. She took it for a test drive around the block—then ten miles down the highway. The range estimator climbed from 20 to 78 miles.
No error. No limp mode. No P155B-00.
Mira pulled into the driveway and sat in the silence, the only sound the soft whir of the cooling fan. She rested her hand on the center console, exactly where Leo used to put his coffee cup.
“You were right,” she said. “It just needed someone to listen.”
And for the first time in a long time, the car—and Mira—felt ready to face the road ahead.
The Nissan trouble code P015B-00 (often searched as P155B) indicates an O2 Sensor Delayed Response from Lean to Rich (Bank 1, Sensor 1). This means the upstream oxygen sensor—the one before the catalytic converter on the side of the engine with cylinder #1—is taking too long to report changes in the air-fuel mixture to the vehicle's computer. Key Summary of P015B-00
What it means: The Powertrain Control Module (PCM) detected that the O2 sensor's signal voltage is fluctuating too slowly between "lean" (high oxygen) and "rich" (low oxygen) states. Common Symptoms: Illuminated Check Engine Light. Noticeable drop in fuel efficiency. Rough idling or a slight loss in engine power. Potential Causes: A faulty O2 sensor (most common). Damaged, corroded, or loose wiring/connectors. An exhaust leak near the sensor. A contaminated or failing catalytic converter. Repair Recommendations
Visual Inspection: Before buying parts, check the wiring harness and connectors for any signs of fraying, melting (from exhaust heat), or corrosion.
Monitor Live Data: Use an OBD-II scanner to watch the O2 sensor voltage while the engine is running at operating temperature. It should cycle rapidly between approximately 0.1V and 0.9V.
Check for Leaks: Inspect the exhaust manifold for cracks or leaking gaskets, as fresh air entering the exhaust can confuse the sensor.
Replace Sensor: If wiring and exhaust are intact, replacing the upstream Bank 1 O2 sensor typically resolves this specific code. Experts recommend using an Oxygen Sensor Removal Tool for easier access.
Understanding the Nissan P155B-00 Code: A Comprehensive Guide
As a car owner, receiving a mysterious error code from your vehicle's onboard computer can be frustrating and worrisome. One such code that has been reported by several Nissan owners is the P155B-00 code. In this article, we will delve into the world of automotive diagnostics and explore the meaning, causes, symptoms, and possible solutions for the Nissan P155B-00 code.
What is the Nissan P155B-00 Code?
The P155B-00 code is a specific error code that is related to the throttle control system in Nissan vehicles. This code is part of the OBD-II (On-Board Diagnostics II) system, which is a standardized system used to monitor and diagnose issues in modern vehicles. The P155B-00 code is specifically related to the electronic throttle control (ETC) system, which is responsible for regulating the throttle's position and airflow into the engine.
Causes of the Nissan P155B-00 Code
The P155B-00 code can be triggered by a variety of factors, including:
Symptoms of the Nissan P155B-00 Code
When the P155B-00 code is triggered, you may notice one or more of the following symptoms:
Diagnosing and Repairing the Nissan P155B-00 Code Key Features
If you suspect that your Nissan vehicle has triggered the P155B-00 code, it's essential to have it diagnosed and repaired by a qualified mechanic. Here are the general steps involved in diagnosing and repairing the P155B-00 code:
Preventing the Nissan P155B-00 Code
While some issues that trigger the P155B-00 code may be unavoidable, there are steps you can take to prevent it:
Conclusion
The Nissan P155B-00 code is a specific error code related to the throttle control system in Nissan vehicles. Understanding the causes, symptoms, and possible solutions for this code can help you diagnose and repair issues promptly. By taking preventative measures and addressing issues promptly, you can minimize the risk of triggering the P155B-00 code and ensure your vehicle runs smoothly and efficiently. If you're experiencing issues with your Nissan vehicle, consult a qualified mechanic for proper diagnosis and repair.
Based on the diagnostic trouble code (DTC) format, P155B-00 is a manufacturer-specific code used by Nissan and Infiniti vehicles.
Here is a detailed breakdown of the code, its meaning, causes, and diagnosis.
Locate the coolant bypass valve—typically on the engine block, near the intake manifold or behind the alternator on QR25DE engines. Look for:
Use a bidirectional scan tool (not just a basic code reader). Clear the code and perform a road test to see if P155B-00 returns immediately.
Nissan has acknowledged cooling system valve issues on several models. For example, NTB12-055 and NTB16-085 cover certain Rogue, Altima, and Sentra models with P155B-00-related symptoms. These TSBs often prescribe a software update and/or valve replacement.
Check with a Nissan dealer using your VIN to see if your vehicle qualifies for a warranty extension or free repair—especially if you are under 80,000 miles.
| Service | Estimated Cost (USD) | |---------|----------------------| | Diagnostic fee | $100 – $150 | | Coolant bypass valve (OEM) | $120 – $250 | | Coolant & supplies | $30 – $60 | | Labor (1.5 – 2.5 hours) | $150 – $300 | | Total at dealership | $350 – $650 | | Total at independent shop | $250 – $450 | | DIY cost | $150 – $300 |
Note: Prices vary by region and model year. V6 engines often require more labor due to tighter access.
The Nissan fault code P155B-00 is a manufacturer-specific diagnostic trouble code (DTC) that indicates a malfunction in the Battery Current Sensor Circuit. This sensor is a critical component in modern Nissan vehicles, as it monitors the rate of charge and discharge for the battery, allowing the Engine Control Module (ECM) to manage the alternator's output and optimize fuel efficiency. Understanding the P155B-00 Code
When your vehicle's computer (PCM/ECM) detects a voltage signal from the battery current sensor that is outside of the expected range, it triggers the P155B-00 code and illuminates the Check Engine Light.
P155B: Refers to the specific circuit malfunction of the battery current sensor.
-00: Is a sub-type indicator often used in modern OBD-II systems to denote a "general failure" or no specific sub-type information available. Common Symptoms
While the most immediate sign is a warning light, you may also experience:
Decreased Fuel Economy: The alternator may run more than necessary, putting extra load on the engine.
Charging System Issues: You might notice flickering lights or a weak battery if the alternator isn't charging correctly.
Auto Start-Stop Failure: On newer models, this system may be disabled because the ECM cannot accurately verify the battery's state of charge. Potential Causes
Corroded Battery Terminals: Heavy corrosion on the terminals can disrupt the sensor's signal or power supply.
Faulty Battery Current Sensor: The sensor itself, typically located on the negative battery cable, may have failed internally.
Wiring Damaged: Frayed, broken, or shorted wires in the sensor's harness.
Weak Battery: A failing battery that cannot maintain proper voltage may lead the sensor to report "out of range" values. Diagnostic and Repair Steps
If you encounter this code, following these steps can help identify the root cause:
Visual Inspection: Check the battery terminals for white or green powdery buildup. Cleaning these with a wire brush and a mixture of baking water and soda is a common first fix.
Check the Sensor Harness: Inspect the small connector going to the negative battery terminal. Ensure it is firmly seated and the wires are not damaged.
Test the Battery: Use a multimeter or visit a retailer like AutoZone or O'Reilly Auto Parts to have your battery and alternator tested for free.
Sensor Replacement: If the wiring and battery are healthy, the current sensor may need replacement. You can find OEM Nissan parts through Nissan USA's parts portal.
Clear the Code: After repairs, use an OBD-II scanner to clear the code and perform a drive cycle to see if the light returns.
The Nissan P155B-00 fault code typically refers to a malfunction within the Selective Catalytic Reduction (SCR) system, specifically involving the Reductant Heater Control Circuit or a general SCR system fault. This code is most commonly seen in modern Nissan diesel vehicles, such as the Navara NP300, that utilize AdBlue (Diesel Exhaust Fluid) to meet strict emission standards. What Does P155B-00 Mean?
The "P155B" prefix indicates a manufacturer-specific code rather than a generic OBD-II code (which usually starts with P0). In the context of Nissan’s SCR system:
Reductant Heater Failure: The engine's computer (ECM) has detected that the heater responsible for keeping the AdBlue fluid from freezing or maintaining its operating temperature is not performing correctly.
Circuit Malfunction: The "-00" suffix often suggests a general failure or a "no sub-type" information status, meaning the circuit is either open, shorted, or the heater itself has failed. Common Symptoms
When this code is triggered, you may notice one or more of the following:
Check Engine Light (MIL): The most obvious sign is the dashboard warning lamp.
AdBlue/DEF Warning: A message stating "SCR System Fault" or "AdBlue Error" may appear.
Engine Derate (Limp Mode): To prevent excessive emissions, the vehicle may limit engine performance by up to 40% or cap the maximum speed.
No-Start Countdown: In severe cases, the vehicle may display a countdown of miles remaining before the engine will no longer start until the system is serviced. Common Causes
Faulty AdBlue Dosing Valve/Injector: The injector can become blocked by crystallized DEF, leading to circuit issues.
Damaged Wiring Harness: The SCR system components are located under the vehicle and are exposed to road debris, water, and heat, which can cause corroded or broken wires.
Defective Reductant Heater: The internal heating element within the DEF tank or the lines may have failed.
Poor DEF Quality: Using contaminated or old Diesel Exhaust Fluid can trigger SCR-related codes. Troubleshooting and Repair Steps
If you encounter the P155B-00 code, follow these diagnostic steps to identify the root cause:
Step 1: Inspect the AdBlue Injector. Locate the AdBlue injector on the exhaust pipe. Check for signs of white "crystal" buildup. You can sometimes clean a blocked injector by soaking the tip in warm water to dissolve the urea crystals.
Step 2: Check Wiring and Connectors. Perform a visual inspection of the wiring harness leading to the DEF tank and the dosing valve. Look for any corrosion or frayed wires that might be causing a short or open circuit.
Step 3: Test Component Resistance. Use a multimeter to check the resistance of the reductant heater and the dosing valve. Compare these readings against the factory specifications found in a Nissan Service Manual.
Step 4: Perform a Forced Reset. After repairs, the code often requires a "Hard Reset" using a professional-grade diagnostic scanner to clear the "SCR System Fault" and end any limp-mode conditions.
Note: SCR repairs can be complex due to the software integration. If cleaning the injector and checking the wiring does not resolve the issue, it is highly recommended to visit a specialist or dealer to ensure the ECM adaptives are properly reset.