Circuit Description
The PCM uses the 5 Volt Reference A circuit as a sensor feed to the following sensors:
| • | The TP sensor. |
| • | The MAP sensor. |
| • | The EGR Valve Pintle Position sensor. |
The PCM monitors the voltage on the 5 Volt Reference A circuit. If the voltage is out of tolerance, the PCM will set DTC P1635.
Conditions for Running the DTC
The ignition is on.
Conditions for Setting the DTC
| • | The PCM detects a voltage out of tolerance condition on the 5 Volt Reference A circuit. |
| • | Above condition for longer than 10 seconds. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecuitive trip in which the diagnostic has been run and failed. |
| • | If equipped with traction control, the PCM will command the EBTCM via the serial data circuit to turn OFF traction control, and the EBTCM will illuminate the TRACTION OFF lamp. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed. |
| • | The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using the scan tool. |
Diagnostic Aids
Check for the following conditions:
| Important: Be sure to inspect PCM and engine grounds for being secure and clean. |
| • | Poor connection at PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. |
| • | Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the MAP display on the scan tool with the ignition on, engine off while moving connectors and wiring harnesses related to the following sensors: |
| • | The MAP sensor. |
| • | The EGR valve. |
| • | TP sensor. |
A change in the MAP display will indicate the location of the fault.
Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.
Test Description
The numbers below refer to the step numbers on the diagnostic table:
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Important: : DTC must have failed this ignition to be properly diagnosed.
The 5 Volt Reference circuits have multiple PCM pins, be sure to test all components on the 5 Volt Reference A circuits only.
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The 5 Volt Reference circuits have multiple PCM pins, be sure to test all components on the 5 Volt Reference A circuits only.
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This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check ? | -- | ||||||
|
Important:: The DTC must have failed this ignition to be diagnosed correctly.
Does the voltage measure near the specified value? | 5.0V | |||||||
With a DMM observe the voltage while disconnecting all components connected to the 5 Volt Reference circuit one at a time. Does voltage change when one of the components is disconnected? | -- | |||||||
4 | Does the voltage measure less than the specified value? | 4.9V | ||||||
5 |
Does the voltage measure near the specified value? | 5.0V | ||||||
6 | Test all 5 Volt Reference A circuits for a short to ground. Refer to Wiring Repairs in wiring systems. Did you find and correct the condition? | -- | ||||||
7 | Test all 5 Volt reference A circuit for a short to voltage. Refer to Wiring Repairs in wiring systems. Did you find and correct the condition? | -- | ||||||
8 | Replace the affected component. Refer to appropriate component replacement. Did you complete the replacement? | -- | -- | |||||
|
Important: : The replacement PCM must be programmed. Replace PCM. Refer to Powertrain Control Module Replacement/Programming Did you complete the replacement? | -- | -- | ||||||
10 | Use the scan tool in order to clear the DTCs Operate the Vehicle within the conditions for running the DTC as specified in the supporting text . Does the DTC reset ? | -- | System OK |
