Diagnostic Instructions
DTC Descriptors
DTC P0642: 5-Volt Reference 1 Circuit Low Voltage
DTC 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
| P0336
| P0335
| P0643 P0336
| --
|
Camshaft 4 X - 5-Volt Reference
| P0642
| P0340
| P0340
| P0643 P0336
| --
|
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
• | 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
• | The control module illuminates the malfunction indicator lamp
(MIL) when the diagnostic runs and fails. |
• | The control module records the operating conditions at the time
the diagnostic fails. The control module stores this information in the Freeze
Frame/Failure Records. |
Conditions for Clearing the MIL/DTC
• | The control module turns OFF the malfunction indicator lamp (MIL)
after 3 consecutive ignition cycles that the diagnostic runs and does
not fail. |
• | A current DTC, Last Test Failed, clears when the diagnostic runs
and passes. |
• | A history DTC clears after 40 consecutive warm-up cycles,
if no failures are reported by this or any other emission related diagnostic. |
• | Clear the MIL and the DTC with a scan tool. |
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Electrical Information Reference
Circuit/System Verification
- Engine starts and runs.
- 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
- Turn OFF the ignition for 30 seconds or until the ECM powers down.
- Disconnect the camshaft position (CMP) sensor.
- Turn ON the ignition, with engine OFF and measure the voltage from the 5-volt reference circuit of the CMP sensor to a good ground with a DMM.
⇒ | If the voltage measures 4.7-5.2 volts, replace the camshaft position sensor. |
- With the DMM still connected to the 5-volt reference circuit, disconnect the crankshaft position (CKP) sensor.
⇒ | If the voltage measures 4.7-5.2 volts, replace the CKP sensor. |
- Test the 5-volt reference 1 circuits for a short to ground or a short to voltage.
⇒ | If no problem was found in the 5-volt reference circuit , replace the ECM. |
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.