P0642-SENSOR REFERENCE VOLTAGE 1 CIRCUIT LOW
P0642-SENSOR REFERENCE VOLTAGE 1 CIRCUIT LOW
For a complete wiring diagram, refer to the Wiring Information.
Theory of Operation
The primary 5-Volt Supply circuit supplies the Crankshaft Position Sensor (CKP), Oil Pressure Sensor (OPS), and Throttle Body Assembly. For self protection, if the 5-Volt Supply circuit is shorted to ground or if one of the sensors is internally shorted, the Powertrain Control Module (PCM) will turn off the 5-Volt Supply circuit until the next ignition cycle.
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When Monitored:
Ignition on.
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Set Condition:
When the Powertrain Control Module (PCM) recognizes the (F855) 5-Volt Supply circuit voltage is too low. One Trip Fault. ETC light is flashing.
Possible Causes |
|---|
| (F855) 5-VOLT SUPPLY SHORTED TO GROUND |
| CRANKSHAFT POSITION SENSOR |
| OIL PRESSURE SENSOR |
| A/C PRESSURE TRANSDUCER |
| THROTTLE BODY ASSEMBLY |
| APP SENSOR |
| POWERTRAIN CONTROL MODULE (PCM) |
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
1. ACTIVE DIAGNOSTIC TROUBLE CODE (DTC)
| NOTE: | Improperly installed aftermarket accessories can cause this DTC to set. Check for any improperly installed aftermarket accessories before continuing with this test. |
| 1. | Turn the ignition on for 60 seconds. |
| 2. | With a scan tool, read the active DTCs. |
Is the DTC Active at this time?
Yes
- Go To 2
No
- Perform the INTERMITTENT CONDITION diagnostic procedure. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
2. (F855) 5-VOLT SUPPLY SHORTED TO GROUND
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| 1. | Turn the ignition off. |
| 2. | Disconnect the PCM C2 harness connector. |
| 3. | Disconnect all the Sensors that share the (F855) 5-Volt Supply circuit. |
| 4. | Disconnect the APP Sensor harness connector. |
| 5. | Measure the resistance between ground and the (F855) 5-Volt Supply circuit in the Throttle Body harness connector. |
Is the resistance below 100 Ohms?
Yes
- Repair the short to ground in the (F855) 5-Volt Supply circuit.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
No
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Go To 3
 |
| 1. | Reconnect all the previously disconnected Sensors except for the CKP Sensor harness connector. |
| 2. | Ignition on, engine not running. |
| 3. | Measure the voltage on the (F855) 5-Volt Supply circuit in the CKP Sensor harness connector. |
Is the voltage below 4.75 Volts?
Yes
- Go To 4
No
- Verify that there is good pin to terminal contact in the CKP Sensor and Powertrain Control Module harness connectors. If OK, replace the Crankshaft Position Sensor. (Refer to 14 - Fuel System/Fuel Injection/SENSOR, Crankshaft Position - Removal) .
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Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM)
- Standard Procedure).
4. 5-VOLT SENSOR SHORTED TO GROUND
| 1. | Measure the voltage on the (F855) 5-Volt Supply circuit at the CKP Sensor harness connector. |
| NOTE: | You must Turn the Ignition OFF when disconnecting any of the Sensor harness connectors and Turn the Ignition On to check the voltage readings. |
| 2. | While monitoring the voltage, disconnect each Sensor harness connector that shares the (F855) 5-Volt Supply circuit, one at a time. |
Does the voltage increase above 4.75 Volts when disconnecting any of the Sensor harness connectors?
Yes
- Verify that there is good pin to terminal contact in the related Sensor and Powertrain Control Module connectors. If OK, replace the Sensor that causes the (F855) 5-Volt Supply circuit voltage to increase when disconnected.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
No
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Go To 5
5. POWERTRAIN CONTROL MODULE (PCM)
| 1. | Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the related Sensors and the Powertrain Control Module (PCM). |
| 2. | Look for any chafed, pierced, pinched, or partially broken wires. |
| 3. | Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the related Sensor and Powertrain Control Module connectors. |
| 4. | Perform any Technical Service Bulletins that may apply. |
Were there any problems found?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
No
- Replace and program the Powertrain Control Module (PCM) in accordance with the Service Information. (Refer to 08 - Electrical/8E - Electronic Control Modules/MODULE, Powertrain Control - Removal) .
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).