P0641Sensor Reference Voltage A Circuit/Open
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- The engine module feeds several sensors (pedal, throttle, pressure and position sensors) from shared, regulated 5 V reference circuits; 'A' is circuit 1. A short on one sensor or its wire pulls down every sensor on that circuit and triggers many follow-up codes – so look for the one faulty sensor or chafed wire, for example by unplugging the sensors one at a time. P0641 is the general code for circuit A. GM puts everything into this one code: reference outside 4.875–5.125 V or jumping (filtered against unfiltered value), 19 of 39 counts or 0.19 s in a row, lamp in the first trip; circuits 2–4 are P0651, P0697 and P06A3, and GM does not use P0642/P0643. GM Europe's 2.0 L diesel flags it outside 4.5–5.5 V for 0.5 s with reduced engine power (two trips), the 2.0 L petrol after 1 s or 10 s cumulative (first trip). Because throttle and pedal sensors may be affected, limp mode is common.
- What you may notice
- Check engine light
- Limp mode with reduced power
- Many codes from several sensors at once
- Possibly starting or boost problems
- Likely causes
- LikelyShort to ground or voltage at one of the supplied sensors or its wire
- PossibleA sensor signal wire shorted to voltage
- PossibleHarness damage (chafing, rodent bite, water in connector)
- RareModule internal (reference regulator)
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.