Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptors
DTC P0642: 5-Volt Reference 1 Circuit Low VoltageDTC P0643: 5-Volt Reference 1 Circuit High Voltage
Diagnostic Fault Information
Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance |
|---|---|---|---|---|---|
Crankshaft 58 X - 5-Volt Reference | P0642 | P0335, P2453 | P0335, P2453 | P0341, P0401, P0643 | -- |
Camshaft 4 X - 5-Volt Reference | P0642 | P0340 | P0340 | P0340, P0401, P0643 | -- |
Intake Air Flow Valve | P0642 | P02E7 | P02E8 | P0401, P0643 | -- |
Fuel Tank Level Sensor 2 | P0642, P2067 | P2068 | P2068 | P0643, P2068 | -- |
Circuit/System Description
The engine control module (ECM) supplies 5 volts to components through 5-volt reference circuits. These 5-volt reference circuits are independent of each other outside the ECM, but are bussed together in three reference groups inside the ECM. Therefore, a circuit condition on one sensor 5-volt reference circuit may affect multiple components. The ECM monitors voltage on the 5-volt reference circuits.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The diagnostics run continuously. |
Conditions for Setting the DTC
P0642
| • | The ECM detects the 5-volt reference 1 circuit voltage is less than 4.7 volts. |
| • | The above condition is present for 2 seconds. |
P0643
| • | The ECM detects the 5-volt reference 1 circuit voltage is more than 5.2 volts. |
| • | The above condition is present for 2 seconds. |
Action Taken When the DTC Sets
DTC P0642 and P0643 are Type A DTCs.
Conditions for Clearing the MIL/DTC
DTC P0642 and P0643 are Type A DTCs.
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
- The engine starts and runs.
- Observe the 5-Volt Reference 1 Circuit Status parameter with a scan tool. The parameter should display OK.
- Engine running, observe the DTC information with a scan tool. DTCs P0642 or P0643 should not set.
- Operate the vehicle within the Conditions for Running the DTC. 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 of all appropriate sensors for the applicable DTC.
- Ignition ON, measure for 4.8-5.2 volts between one of the 5-volt reference circuits and ground.
- Connect each component associated with the 5-volt reference circuit, one at a time, while monitoring the voltage. The voltage should not change more than 1 volt.
Important: A short to voltage on the signal circuit of certain components may cause this DTC to set.
| ⇒ | If the voltage is 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 ECM. |
| ⇒ | If the voltage is greater than the specified range, test for a short to voltage on all the 5-volt reference circuits. If all circuits test normal, replace the ECM. |
| ⇒ | If the voltage display increases greater than the specified value when a component is connected, test the signal circuit for a short to voltage. If all circuits test normal, replace the ECM. |
| ⇒ | If the voltage display decreases more than the specified value when a component is connected, replace the component. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ECM replacement, setup, and programming |
