Diagnostic Instructions
DTC Descriptors
DTC P0641: 5-Volt Reference 1 Circuit
DTC P0651: 5-Volt Reference 2 Circuit
Circuit/System Description
The engine control module (ECM) has 2 5-volt reference circuits. The ECM provides the 5-volt reference to various sensors. Each reference circuit provides a 5-volt reference for greater 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.
Conditions for Running the DTC
| • | DTCs P0641 and P0651 run continuously when the above condition is met. |
Conditions for Setting the DTC
The control module detects a voltage above 5.5 volts, or below 4.5 volts, on either 5-volt reference circuit for greater than 0.5 second.
Action Taken When the DTC Sets
| • | DTCs P0641 and P0651 are Type B DTCs. |
| • | The ECM commands the TAC system to operate in a Reduced Engine Power mode. |
Conditions for Clearing the DTC
DTCs P0641 and P0651 are Type B DTCs.
Diagnostic Aids
| • | If a shared 5-volt reference circuit is shorted to ground or shorted to a voltage, other 5-volt reference circuits may be affected. |
| • | The scan tool 5 volt reference parameter should display between 4.6-5.4 volts. |
P0641
The 5-volt reference 1 circuit provides 5 volts to the following sensors:
| • | The accelerator pedal position (APP) sensor 1 |
| • | The throttle position (TP) sensor 1 |
| • | The throttle position (TP) sensor 2 |
P0651
The 5-volt reference 2 circuit provides 5 volts to the following sensors:
| • | The accelerator pedal position (APP) sensor 2 |
| • | The air conditioning (A/C) refrigerant pressure sensor |
| • | The exhaust gas recirculation (EGR) valve |
| • | The fuel tank pressure (FTP) sensor |
| • | The intake manifold tuning (IMT) valve position sensor |
| • | The manifold absolute pressure (MAP) sensor |
Reference Information
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
Circuit/System Verification
- Ignition ON, observe the DTC information with a scan tool. DTCs P0641 and P0651 should not set.
- 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.
Circuit/System Testing
Important: Additional DTCs will set when disconnecting the components.
- Ignition OFF, disconnect the harness connector of all appropriate sensors for the applicable DTC. Refer to Diagnostic Aids.
- Ignition ON, measure for 4.6-5.4 volts between one of the 5-volt reference circuits and ground.
| ⇒ | If the voltage is less than the specified value, 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 the specified
value, 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.
- Connect each component associated with the 5-volt reference circuit one at a time while monitoring the scan tool 5 volt reference parameter. The voltage should not change greater than 0.5 volt.
| ⇒ | If the voltage display is not within the specified range when a component is connected, replace the component. |
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
