P0641

Sensor Reference Voltage "A" Circuit Open

DTC P0641, sometimes indicated as P064100 is an OBD diagnostic trouble code indicating a generic fault with the vehicle powertrain (i.e. engine and gearbox). This code identifies an error with the causing sensor reference voltage "a" circuit open.

This code is set when the PCM detects an open or shorted condition in the voltage reference circuit for the A side of the engine coolant temperature sensor. This sensor is used by the PCM to calculate the engine coolant temperature.
Possible causes of this code include a bad engine coolant temperature sensor, a wiring problem, a bad PCM, or a problem with the powertrain control module ground.
If this code is present, check the engine coolant temperature sensor for proper operation. If the sensor is good, check the wiring and connectors for damage or corrosion. If the wiring and connectors are good, then the PCM may need to be replaced.

  • P0641: Sensor Reference Voltage A Circuit Open
  • P0641: Sensor Reference Voltage "A" Circuit Open
  • P0641: Sensor Reference Voltage "A" Circuit/Open
  • P0641: Sensor A Reference Voltage Circuit Open
  • P0641: Sensor reference voltage A – open circuit
  • P0641 00: Sensor reference voltage A - open circuit

See Also: Related Error Codes
DTC Trouble Code Search
Bulletins

Bulletins are notices put out by manufacturers in conjunction with the NHTSA to notify the public of manufacturing issues or changes.

  • PIP5724 - ENGINE AND ENGINE COOLING
    CHEVROLET: This preliminary information communicates the vehicle may have an ses lamp with any of the following dtc P06DA, P06DB, P06DC, P250A, P0300, P0340, P0341, P0335, P0336, P0641, P0011, P0010, P2088, P2089, and/or P2230. Possible crank no s
  • PIP5553A - ELECTRICAL SYSTEM
    CHEVROLET: This preliminary information communicatesthe vehicle may have an ses lamp with any of the following dtc P06DA, P06DB, P06DC, P250A, P0300, P0340, P0341, P0335, P0336, P0641, P0011, P0010, P2088, P2089, and/or P2230. Possible crank no start
  • PIC5606A - ELECTRICAL SYSTEM:WIRING
    CHEVROLET: This preliminary information communication provides information to the technicians about vehicles that may have a service engine soon malfunction indicator lamp on. Technician may find diagnostic trouble codes P069E, P0641, and B101D. Techn
  • PIP5553 - ELECTRICAL SYSTEM:STARTER ASSEMBLY
    CHEVROLET: This preliminary information communicatesthe vehicle may have an ses lamp with any of the following dtc P06DA, P06DB, P06DC, P06B6, P06B7, P250A, P0300, P0340, P0341, P0335, P0336, P0641, P0011, P0010, P2088, P2089, and/or P2230. Possible c
  • PIP5444 - FUEL SYSTEM, GASOLINE
    CHEVROLET: This preliminary information communication provides information to the technician about vehicles that have a check engine malfunction indicator lamp on. Technician will find diagnostic trouble code P0641. Technician will need to unplug the
Consumer Complaints for this DTC


2010 CHEVROLET COBALT with 107225. miles

While driving on nys i-90, my 2010 Chevrolet Cobalt ls 2010 went into "engine power reduced" and i was not able to drive over 40 mph. I pulled off to the shoulder and waited for about 10 minutes. I started back up, check engine light remained on and car stays in limp mode. The vehicle now idles rough, accelerates slow when at red lights and stop signs and bucks when shifting gears. First at 10 mph (hard buck) than (lighter buck) at 20 mph, and continues lighter through acceleration. Codes that are coming up are P0107 engine (map) barometric pressure circuit - low input, P0452 engine (evaporative emission system pressure system pressure sensor - switch low input, P0532 engine ac pressure sensor a - circuit low, and P0641 engine (sensor reference voltage a) circuit/open. I was able to clear out all codes except for P0641 (permanent). Please help.
POWER TRAIN, ELECTRICAL SYSTEM ENGINE


2010 CHEVROLET COBALT

Vehicle is a 2010 chevy Cobalt 2.2 ecotech (base model). On start up check engine light appears with message engine power reduced. Check engine code is P0641. Replaced multiple sensors, throttle body, checked for wire issues etc. Dealer replaced ecm and still having issues. Can not drive over 40mph or engine with disable. Car hesitates and bucks while driving in engine reduced mode.Car has 68,789 miles.
ENGINE, ELECTRICAL SYSTEM


2010 CHEVROLET COBALT with 188520. miles

My Cobalt illuminates the check engine light as well as the theft light and displays engine power reduced happens multiple times first time it started was in 12/2017. The car was purchased in 2011 always serviced and repaired by dealer ship. The car stalls at stop signs lights or when you pull into a parking lot. Engine light comes and goes. Lights dim and flicker the gauges jump up and down in the dash. After you shut the car off the gauges in the instrument cluster jump adn make ticking noise. When there is no engine light present the car idles rough and acts like its going to die till you start driving then its fine. The issue with the brakes are when you to press them the pedal will depress all the way but its like it dont meet with the pad, this problem is intermittent as well. Obd2 codes have been P0641 P0017 P0651 P0573 current codes stored are P0340 P0300 P0341. I've had this car at the dealer and multiple shops on multiple occasions now without resolution. It's becoming more of a problem than anything especially when your on the interstate and it dies or coming up to a stop light/ sign, a car pulls out or an animal and your brakes fail to stop you! It is a very scary situation. The car does have high miles but i have not had any problems till december of 2017 mileage is 203,602 all maintenance is performed under recommended mileage.
EXTERIOR LIGHTING, SERVICE BRAKES ELECTRICAL SYSTEM

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