P0641: Sensor Reference Voltage A Circuit/Open

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.

Medium severity. Can I keep driving?It depends on the symptoms. If the car is running normally you can go to a repair shop; if it goes into limp mode, drive as little as possible.

Symptoms

Check engine light
Limp mode with reduced power
Many codes from several sensors at once
Possibly starting or boost problems

Most likely causes

Short to ground or voltage at one of the supplied sensors or its wire
A sensor signal wire shorted to voltage
Harness damage (chafing, rodent bite, water in connector)
Module internal (reference regulator)

What to check, in order

Start with the simplest. You can tick off each step.

Check the battery and grounds
Check the continuity of the wire between the component and the control module.
Clear the code and see if it returns
If it is a reference voltage code, disconnect sensors one at a time and see if the voltage recovers
Check whether a software update is available
Do not replace the control module without a full diagnosis

Good to know

Repair difficulty: medium
It can trigger limp mode.
It affects emissions.

What each character of P0641 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
6: Control modules and outputs
41: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0641?

It depends on the symptoms. If the car is running normally you can go to a repair shop; if it goes into limp mode, drive as little as possible.

What causes code P0641?

The most common causes are: short to ground or voltage at one of the supplied sensors or its wire; a sensor signal wire shorted to voltage; harness damage (chafing, rodent bite, water in connector).

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.