Powertrain, generic · Computer and auxiliary outputs

P0641 Sensor Reference Voltage A Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

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)

Symptoms

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

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–900
Time0.5–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

sensor reference voltage circuitsensor wiringengine control module

Related codes

P0642P0643P06A6P0651P0697P06A3

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com, saabwisonline.com.