Sensor Reference Voltage "B" Circuit Low
P0652 indicates that the engine control module detected low voltage in the Sensor Reference Voltage B circuit, which supplies power to various engine sensors. This prevents proper sensor operation and can affect engine performance and transmission shifting.
What You Might Notice
- Check Engine Light illuminated
- Transmission may fail to shift properly between modes
- Rough idle or unstable engine operation
- Reduced fuel economy
- Difficulty starting or stumbling on acceleration
Most Common Causes
- 1
Faulty system power relay
The relay that supplies voltage to the sensor reference circuit may be defective or stuck open, preventing proper voltage from reaching the sensors.
- 2
Blown fuse or fusible link
An open or blown fuse in the sensor reference circuit will block voltage supply to the circuit, triggering the low voltage code.
- 3
Bad reference voltage sensor
The sensor itself may be defective and unable to maintain proper voltage communication with the engine control module.
- 4
Open circuits or corroded connectors
Wiring harness breaks, corrosion, or loose connectors in the reference voltage circuit will cause voltage loss and circuit faults.
How to Diagnose It
- 1
Check Faulty system power relay — The relay that supplies voltage to the sensor reference circuit may be defective or stuck open, preventing proper voltage from reaching the sensors.
- 2
Check Blown fuse or fusible link — An open or blown fuse in the sensor reference circuit will block voltage supply to the circuit, triggering the low voltage code.
- 3
Check Bad reference voltage sensor — The sensor itself may be defective and unable to maintain proper voltage communication with the engine control module.
- 4
Check Open circuits or corroded connectors — Wiring harness breaks, corrosion, or loose connectors in the reference voltage circuit will cause voltage loss and circuit faults.
How to Fix It
- 1
Inspect and test power relay
Locate the sensor reference voltage power relay and test it with a multimeter. Replace if defective or contacts are corroded.
- 2
Check and replace fuses
Inspect the fuse panel for blown fuses related to sensor circuits. Replace any open or blown fuses with the correct amperage rating.
- 3
Clean and inspect connectors
Examine all connectors in the sensor reference voltage circuit for corrosion, loose pins, or damage. Clean with electrical contact cleaner or replace connector if damaged.
- 4
Test and replace reference voltage sensor
Use a diagnostic scanner to verify voltage output at the sensor. If voltage is below specification (typically 4.5-5.5V), replace the defective sensor.
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