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
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Ignition ON, observe the DTC information with a scan tool. DTCs P0641 and P0651 should not set.
- Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
Important: Additional DTCs will set when disconnecting the components.
- Ignition OFF, disconnect the harness connector at all appropriate sensors for the applicable DTC. Refer to Diagnostic Aids.
- Ignition ON, test for 4.6-5.4 volts between one of the 5-volt reference circuits and ground.
| ⇒ | If less than the specified range, test for a short to ground on all the 5-volt reference circuits. If all circuits test normal, replace the control module. |
| ⇒ | If greater than the specified range, 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 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.
