P1635

Circuit Description

The PCM uses the 5 Volt Reference A circuit as a sensor feed to the following sensors:

^ 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 Setting the DTC

The engine is running.

Conditions for Setting the DTC

^ The PCM detects a voltage out of tolerance condition on the 5 Volt Reference A circuit.
^ The above condition is present for longer than 10 seconds.

Action Taken When the DTC Sets

^ The PCM will illuminate the MIL during the second consecutive trip in which the diagnostic test has been run and failed.
^ The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail Records data.

Conditions for Clearing the MIL/DTC

^ The PCM will turn the MIL OFF 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

Important: Be sure to inspect PCM and engine grounds for being secure and clean.

Check for the following conditions:

^ Poor connection at PCM - Inspect harness connectors for the following items:
- Backed out terminals
- Improper mating
- Broken locks
- Improperly formed or damaged terminals
- Poor terminal to wire connections
^ 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 not running while moving connectors and wiring harnesses related to the following sensors. A change in the MAP display will indicate the location of the fault.
- The MAP sensor
- The EGR valve

Review the Freeze Frame/Fail Records vehicle mileage since the diagnostic test last failed. This may help determine how often the condition that caused the DTC to be set occurs.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

4. This step isolates the 5.0 volt reference circuit from the sensor signal circuit.