The engine control module (ECM) has 3 5-volt reference circuits. The ECM provides the 5-volt reference to various sensors. Each reference circuit provides a 5-volt reference for more than one sensor. A short to ground or voltage on one of the 5-volt reference circuits will affect all components connected to that 5-volt reference circuit. The ECM monitors the voltage on the 5-volt reference circuits.

The 5-volt reference 2 voltage is above or below a predetermined threshold for more than 4 seconds.

DTC P0651 is Type B DTC.

DTC P0651 is Type B DTC.

The 5-volt reference 2 circuit provides 5 volts to the following sensors:

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

1. Ignition ON, observe the DTC information with a scan tool. DTC P0651 should not set.
2. If the vehicle passes the Circuit/System Verification test, operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records List.

Important: Additional DTCs will set when disconnecting the components.

1. Ignition OFF, disconnect the harness connector of all appropriate sensors for the applicable DTC. Refer to Diagnostic Aids.
2. Ignition ON, measure for 4.6-5.2 volts between one of the 5-volt reference circuits and ground.

⇒	If the voltage is less than 4.6 volts, test for a short to ground on all the 5-volt reference circuits. If all circuits test normal, replace the control module.

⇒	If the voltage is greater than 5.2 volts, test for a short to voltage on all the 5-volt reference circuits for each component associated with the appropriate 5-volt reference circuit. If all circuits test normal, replace the control module.

Important: A short to voltage on the signal circuit of certain components may cause this DTC to set.

3. Connect each component associated with the 5-volt reference 2 circuit one at a time while monitoring the 5-Volt Reference 2 Circuit Status parameter with a scan tool. The parameter should continue to display OK.

⇒	If the parameter displays Fault when a component is connected, test the signal circuit of that component for a short to voltage. If the circuit tests normal, replace the component.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.