What is the P0641 fault codes? What is the description of the P0641 Sensor Reference Voltage “A” Circuit Open error code? How can you fix P0641 fault codes? What are the symptoms and causes for the P0641 fault code
A P0641 code indicates that there has been a fault detected in the “Sensor Reference Voltage” “A” circuit. This code is general for vehicles with OBD-II systems from 1996 to present. The vehicle make and model may affect the description, troubleshooting, and repair methods.
If the PCM detects an error at the reference voltage of any sensor, the fault code P0641 is set. Circuit A refers to circuits that supply voltage for sensors associated with the differential, driveline, and transmission. Circuit “B” refers to the sensors that control the engine or drive functions. Noting that both circuits have multiple sensors, a fault in “A” circuit can affect all sensors and subsystems. This code is often accompanied by another code that indicates the fault of the sensor. If P0641 doesn’t set itself, it could be due to an error in PCM programming or a problem with software.
NOTE: Hall-effect sensors don’t require a reference voltage because they generate their signal currents through a magnetic field. These sensors are not affected by the code.
In some cases, the engine fault light may come on when Code P0641 is used. To illuminate the engine fault lamp, you will need to have more than one fault code. Before you start the repair, wait for the PCM’s readiness. Clear the fault codes after each repair or intervention and then drive the vehicle as normal.
P0641 Malfunction Symptoms
The severity of the code P0641 depends on which sensor circuit was left open. This code typically displays the following symptoms.
- – Illumination for the check engine light
- – The engine might not start or run well.
- – An increase of fuel consumption
- – Reduced engine performance
- Engine misfires
- – Transmissions may not shift into the right gear at all, or may have rough, laggy or erratic gear changes
- – Unable to switch between economy mode and sport mode by the transmission
- – The transmission cannot switch between two-wheel and four-wheel drive modes.
- Transmission is not shifting from low to high gear
- – Front and center differentials may not engage
- Faulty speedometer/odometer not working or not working
Causes of the P0641 Fault code
These could be the causes for this engine code:
- – Broken, melted or corroded cables or connectors connecting control modules to the PCM.
- – Blown Fuses
- – Defective power relay
- – Electrical components and cables causing an open circuit or short circuit in the engine sensors
- – Bad electrical connection or ground wire to the PCM input circuit
- – Defective engine sensor(s)
- – Defective PCM
Fault Detection & Repair Procedures
Notify us of any errors. You can check the order they appear if there are any additional codes. Codes that were not P0641 might have caused P0641. These codes should first be examined and decoded. Failing to do this will lead to wasted time and unnecessary replacement of components.
You should test the circuit for system fuses or fuse connections when it is under full load. Even though they may appear normal under a light load, fuses that fail under full load often fail. Fuses that are suspected or blowing should be replaced.
You should inspect all wiring and connections that are related to the sensor systems. If necessary, damaged, corroded and corroded cables, connectors, and components should be repaired or replaced.
The reference voltage of the sensor should be checked to make sure that all wiring and fuses are in good condition. It is important to measure the resistance and continuity parameters values of the sensor. You should verify that the measured values are consistent with vehicle specific sensor characteristics. Replace any sensor that does not conform to these specifications. You should pay particular attention to malfunctions or circuits that are open.
- Repair or replace damaged, disconnected and corroded components and wires to the PCM.
- – Replacing blown fuse
- – Replacement of the defective sensor or detection
- – Replace all deficient control modules
- – Replacing the faulty PCM
Reprogramming a control module is required if it needs to be replaced. After a few driving cycles, you will encounter numerous fault codes if the mechanic has not programmed the module. A poorly programmed PCM could prevent your vehicle from starting.
