OBD-II code · Powertrain (generic)
P0641 Sensor Reference Voltage "A" Circuit Open
The 5 V reference voltage that the ECU supplies to multiple sensors (TPS, MAP, accelerator pedal, etc.) has dropped out or is open-circuit. Symptoms cascade — many sensor codes appear at once, all related to the same reference rail.
Is it safe to drive with P0641?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyReference wire shorted to ground (one defective sensor pulls the rail down)
- PossibleECM internal reference output failed
- Less likelyPin pushed back out of connector body
Symptoms
- Check engine light on
- Possible limp mode or no-start
- Multiple follow-up faults across modules
- Reset/relearn may be needed after repair
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1–6 h
- Emissions test
- Likely to fail
- Parts involved
- Ecm, Sensor Reference Wiring
Related codes
- P063EAuto Configuration Throttle Input Not Present Bank 1
- P063FAuto Configuration Engine Coolant Temperature Input Not Present
- P0640Intake Air Heater Control Circuit
- P0642Sensor Reference Voltage "A" Circuit Low
- P0643Sensor Reference Voltage "A" Circuit High
- P0644Driver Display Serial Communication Circuit
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.