Simos 33a Pinout Top (iPad)

| Symptom | Check Pin(s) | |-----------------------------|----------------------------------------| | No power, no communication | 1, 2, 3 (power & ground) | | No start (crank, no spark) | 8, 9 (RPM sensor) & 16, 17 (coils) | | No start (no fuel) | 11–24 injector control, 13 (fuel relay)| | Rough idle | 25–28 (IAC), 6 (TPS), 20 (ECT) | | Rich/lean running, lambda fault | 19 (O2 signal), 31 (O2 heater) | | No EGR / emissions test fail| 14 (EGR control), 15 (SAI) | | No MAP correlation | 29 (MAP signal), 30 (MAP ground) |

Before trying to communicate with the ECU, you must power it up correctly on the bench.

Pro Tip for Bench Testing: When powering the SIMOS 33A on a bench, you need to supply Terminal 30 (12V+) and Terminal 15 (Ignition 12V+), along with a solid **Ground

Based on the query "simos 33a pinout top" (referring to the top side of the ECU board), here is the Siemens/Continental SIMOS 33A (also known as SIMOS 3.3 or 3.4) top-side pinout.

This is the 60-pin connector layout (viewed from the component side / top side of the PCB, looking into the connector pins).

To read or write the Simos 33A on a bench, you need to connect:

Tip: On the top side, you can also use TP24 (CAN_H) and TP23 (CAN_L) as solder points for bench harnesses. simos 33a pinout top

| Symptom | Likely Cause | Top-Side Test | | :--- | :--- | :--- | | No communication (OBD) | CAN bus short or transceiver dead | Measure resistance between Pin 23 & 24 – should be 60Ω (with bus loads). | | ECU won't wake up | No KL15 signal | Probe Pin 5 (Top view) – 0V key off, 12V key on. | | Random misfires on one cylinder | Injector driver FET shorted | Measure pin to ground (e.g., Pin 48). If <10Ω, FET is dead. | | 5V sensor fault (P0641, P0651) | 5V reference shorted to ground | Unplug sensors; measure Pin 31 & 32 to ground. If still 0V, internal failure. |

If you are involved in ECU repair, chip tuning, or engine diagnostics for the VAG group (Volkswagen, Audi, Skoda, Seat), you have likely encountered the SIMOS 33A. This Engine Control Unit (ECU) is a staple in many 1.4L and 1.6L engines from the mid-2000s to early 2010s.

While the SIMOS family is robust, issues often arise that require pinout verification—whether you are bench testing a used unit, repairing a damaged connector, or wiring in a replacement ECU. In this guide, we break down the critical details of the SIMOS 33A pinout, focusing specifically on the "Top" connector and how to navigate its layout safely.

| Signal Type | Example Pins | |---------------------|-------------------| | Power (12V) | 1, 3 | | Ground | 2, 7, 18, 30 | | 5V analog input | 6, 20, 29 | | Frequency input | 8, 9, 32 | | Low-side output | 11–13, 14, 16, 17, 23, 24, 31 | | Stepper motor | 25, 26, 27, 28 | | Shield/shield ground| 10, 22 |

If you are working on a specific engine code or vehicle, I can refine the pinout further (e.g., AZD, AEX, BCA differences). Do you have a specific ECU part number or VIN range in mind?

| Pin | Typical Wire Color | Function | Notes / Conditions | |-----|--------------------|-----------------------------------------------|----------------------------------------------| | 1 | Red/Yellow | Permanent battery voltage (ECU main power) | 30a, fused | | 2 | Brown | ECU ground (main chassis ground) | GND, connects to engine block / chassis | | 3 | Black/Yellow | Ignition switched power (15) | Provides +12V when key is in ON/START | | 4 | - | Not connected | | | 5 | - | Not connected | | | 6 | Grey/Red | Throttle position sensor (TPS) – signal | Linear 0-5V output | | 7 | Brown/Green | Intake air temperature (IAT) – sensor ground | Shared sensor ground | | 8 | Yellow/Black | Engine speed sensor (RPM) – signal positive | Variable reluctance sensor | | 9 | Yellow/Blue | Engine speed sensor – signal negative | | | 10 | Blue/Black | Knock sensor – signal | Shielded wire | | 11 | Green | Injector cylinder 3 – control (ground switch) | Low-side output | | 12 | Grey/White | Injector cylinder 1 – control | | | 13 | Green/Yellow | Fuel pump relay control | Activates relay (ground trigger) | | 14 | Green/White | EGR valve (if equipped) – control | PWM output | | 15 | Black/Green | Secondary air injection relay (if equipped) | Ground trigger | | 16 | White/Green | Ignition coil – cylinder 1 & 4 control | Waste-spark ignition (paired) | | 17 | White/Black | Ignition coil – cylinder 2 & 3 control | Waste-spark ignition (paired) | | 18 | Brown/Yellow | Lambda (O2) sensor – heater ground | Shared sensor return | | 19 | White/Yellow | Lambda (O2) sensor – signal (bank 1) | 0-1V narrowband | | 20 | Blue/White | Coolant temperature sensor – signal | NTC sensor, voltage divider | | 21 | - | Not used | | | 22 | Brown/Red | Engine speed sensor – shield / ground | | | 23 | Blue/Grey | Injector cylinder 4 – control | | | 24 | Brown/Black | Injector cylinder 2 – control | | | 25 | Black/Grey | Idle air control (IAC / idle stepper) – coil A| Bipolar stepper motor | | 26 | Brown/White | IAC – coil B | | | 27 | Black/Blue | IAC – coil C | | | 28 | Brown/Red | IAC – coil D | | | 29 | White/Grey | MAP sensor – signal (if speed-density system) | 0-5V output | | 30 | Brown/Blue | MAP sensor – ground | | | 31 | Yellow/Grey | Oxygen sensor heater – control (ground side) | PWM driven | | 32 | Blue/Yellow | Camshaft position sensor (if equipped) – signal| Used for sequential injection (late SIMOS 33A)| Before trying to communicate with the ECU, you

Note: Pins may be arranged on two rows (1-16, 17-32) or (1-20, 21-40) depending on plastic housing revision.

Mastering the Simos 33A pinout top is essential for anyone working on modern Fiat, Alfa Romeo, Suzuki, or GM small-displacement turbo engines. The 154-pin top layout groups battery and ground on the left (pins A1–A8), injectors and ignition on the right (B1–B6), and sensors/diagnostics along the middle rows (C/D).

Before probing or flashing, memorize the critical pins: Battery = A1–A3, Ignition = A7, Ground = A4–A6, CAN = D1/D2. With this guide and a multimeter, you can confidently bench-test, repair, or retune this powerful yet delicate ECU.

Have a specific Simos 33A pinout question? Leave a comment or contact our support team for vehicle-specific diagrams.

The Siemens Simos 3.3A is a common engine control unit (ECU) found in VAG group vehicles (Volkswagen, Audi, Skoda, Seat), particularly for the 1.6L petrol engines (engine code BFQ).

A "top" pinout typically refers to the connection layout required for bench flashing or boot mode work using tools like OBDSTAR DC706 or MPPS. Simos 3.3A Bench Pinout Guide Pro Tip for Bench Testing: When powering the

When looking at the ECU connector pins from the front (connector side), use these primary connection points for basic communication: Permanent Power (+12V): Pin 3 and Pin 62. Ignition Power (+12V): Pin 1. Ground (GND): Pin 2. K-Line (Communication): Pin 43. CAN High (if applicable): Pin 119. CAN Low (if applicable): Pin 120. Key Technical Resources Siemens Simos 3.3 VAG (Audi, Seat, Skoda, Volkswagen)

The Simos 3.3A (often found in VAG 1.6L vehicles like the VW Golf, Jetta, or Audi A3) typically uses an 80-pin connector. For bench operations like reading pincodes or immobilizer service, specific "top" pins are used to power the unit and establish communication. Bench Connection Pinout

For direct wiring or "bench mode" using tools like the OBDSTAR DC706, the following standard pin assignments are used: +12V (Power): Pin 1 and Pin 3 Ground (GND): Pin 2 Ignition: Pin 62 K-Line (Communication): Pin 43 Internal Components

If you are opening the ECU for boot mode or repair, the SIMOS 3.3 board contains key ICs that control engine functions: Processor: Often a Siemens or Infineon C167 series. EEPROM: Typically a for immobilizer data storage. Flash: Usually a or 29F200 chip for the main engine map. Wiring Context

In vehicle wiring diagrams, the Simos control unit (J361) is centrally located in the plenum chamber and connects via the 80-pin T80 connector. Standard engine sensor pins include: Engine Speed Sensor (G28): Pin 82 Oxygen Sensor (G39): Pins 70, 71 Throttle Position Sensor (G79): Pin 73

Simos Control Unit Wiring Diagram | PDF | Fuel Injection - Scribd