Sensor Reference Voltage B Circuit/Open

Where it lives

For P0651, the circuit described runs through the sensor. The description of P0651 reports the sensor as open.

Check these first

• An open in the 5 volt reference B wire
• A short in a sensor on the reference B circuit
• Corrosion at a sensor connector on reference B
• A failed sensor dragging the reference down
• A faulty ECM reference output

What to do next

1. Check the reference B voltage at each sensor on the circuit
2. Unplug sensors one at a time to find the pull down
3. Inspect the connectors and wiring on reference B
4. Repair the open in the reference B wire
5. Replace the ECM if reference B is dead with the circuit good
6. Clear the code and retest

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