P0643-SENSOR REFERENCE VOLTAGE 1 CIRCUIT HIGH
For a complete wiring diagram, refer to the Wiring Information.
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Theory of Operation
The Powertrain Control Module (PCM) contains two internal 5-Volt Sensor Supply sources. Each 5-Volt Supply source is split into parallel circuits to provide a 5.0 volt reference to multiple three wire sensors. For self protection, if the 5-Volt Supply circuit is shorted to ground or if one of the sensors is internally shorted, the PCM will turn off the 5-Volt Supply circuit until the next ignition cycle.
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When Monitored:
With the ignition on.
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Set Condition:
The Powertrain Control Module (PCM) detects that the 5-Volt supply circuit voltage is above the maximum acceptable value. One Trip Fault. ETC light is flashing.
Possible Causes |
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| (F855) PRIMARY 5-VOLT SUPPLY CIRCUIT SHORTED TO VOLTAGE |
| (F852) ACCELERATOR PEDAL POSITION SENSOR 1 SUPPLY SHORTED TO VOLTAGE |
| 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).
Diagnostic Test
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 at least 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) PRIMARY 5-VOLT SUPPLY SHORTED TO VOLTAGE
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| 1. | Turn the ignition off. |
| 2. | Disconnect the C2 PCM harness connector. |
| 3. | Disconnect all the Sensor harness connectors that share the (F855) Primary 5-Volt Supply circuit. |
| 4. | Ignition on, engine not running. |
| 5. | Measure the voltage on the (F855) Primary 5-Volt Supply circuit in the CKP Sensor harness connector. |
Is there any voltage present?
Yes
- Repair the short to voltage in the (F855) Primary 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
3. (F852) ACCELERATOR PEDAL POSITION SENSOR 1 SUPPLY SHORTED TO VOLTAGE
| 1. | Turn the ignition off. |
| 2. | Disconnect the C1 PCM harness connector. |
| 3. | Disconnect the APP Sensor harness connector. |
| 4. | Ignition on, engine not running. |
| 5. | Measure the voltage on the (F852) Accelerator Pedal Position Sensor 1 Supply circuit in the APP Sensor harness connector. |
Is there any voltage present?
Yes
- Repair the short to voltage in the (F852) Accelerator Pedal Position Sensor 1 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 4
4. 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).