M50 TPS pinout
AMP EFI MSPNP-Pro B8793 E30 plug-and-play wiring:
| Factory E30 throttle-switch connector | MSPNP-Pro B8793 ECU connection | M50 TPS connection |
|---|---|---|
|
Pin 1 Brown/blue wire |
ECU pin 52 TPS signal |
Pin 2 TPS signal |
|
Pin 2 Brown wire |
Sensor ground Sensor return |
Pin 1 Sensor ground |
|
Pin 3 Brown/black wire |
ECU pin 53 5V reference (Vref) |
Pin 3 5V reference (Vref) |
Why the original TPS wiring cannot simply be reused
The original M20/M30 three-pin TPS is generally an idle/WOT switch. The M50 TPS is a potentiometer that produces a continuously changing voltage. Both have three terminals, but their functions are different.
Identify the MegaSquirt wires
MegaSquirt pin numbers are not universal. MS2, MS3, MicroSquirt, relay-board, DIY and PNP harnesses use different ECU terminals. Use the manual for the exact ECU and harness.
- From the correct manual, identify 5V Vref, TPS input and sensor ground.
- With ECU power off and the ECU unplugged, use continuity mode to trace each harness wire to its documented ECU terminal. Never continuity-test a powered circuit.
- Label the wires VREF, SIGNAL and SENSOR GROUND.
- Reconnect the ECU but leave the TPS unplugged. Key on, engine off: measure between the identified Vref and sensor-ground wires. It should be approximately 5V. If it is 0V, near 12V or unstable, stop.
Use the ECU's dedicated sensor ground, not chassis ground. Never connect 5V Vref to 12V or directly to ground.
Connect the M50 TPS
- M50 pin 1 → MegaSquirt sensor ground
- M50 pin 2 → MegaSquirt TPS signal input
- M50 pin 3 → MegaSquirt 5V Vref
Inspect the crimps, pull-test each wire and confirm the terminals are locked into the correct numbered cavities. Do not blindly swap pins because an online example uses a different ECU or connector view.
Test before starting the engine
- Reconnect the TPS. Key on, engine off.
- Back-probe pin 3 to pin 1: approximately 5V.
- Back-probe pin 2 to pin 1 while slowly opening the throttle.
- The signal should rise smoothly from a low closed-throttle voltage toward the upper part of the 0–5V range. It must not jump, drop out or reach 12V.
- Confirm the same smooth movement on the TPS gauge in TunerStudio.
Calibrate it in TunerStudio
- Key on, engine off.
- Open Tools → Calibrate TPS.
- Throttle closed: click Get Current beside closed throttle.
- Throttle fully open: click Get Current beside full throttle.
- Click Accept and verify an approximately 0–100% smooth reading.
If it does not work
- No 5V: check the Vref wire and unplug other sensors that may be pulling down the shared 5V circuit.
- Stuck at 0% or 100%: check for an open signal wire, wrong cavity or missing sensor ground.
- Reads backwards: recheck the molded pin numbers, connector view and sensor part/application. Do not guess and swap terminals.
- Jumpy signal: check crimps and make sure the TPS returns to ECU sensor ground instead of chassis or a high-current ground.
Parts for the conversion
Mounts the M50 TPS and includes the O-ring seal and hardware.
View the adapter →
Housing, boot and contacts for a fresh plug or adapter harness.
View the connector →
Need a custom BMW wiring harness?
Falk Manufacturing builds custom and small-run BMW adapter harnesses. The M20-to-M50 TPS adapter harness shown here is one example of a clean, reversible connector conversion that avoids cutting the original engine harness.
Have a different connector conversion or harness-repair project? Email info@falkmfg.com with the vehicle year and model, engine and ECU information, clear photos of both connector faces, and any available pinout information. I’ll review the project and do my best to develop a solution for you.
View the M20-to-M50 TPS harness example →