P1635

CIRCUIT DESCRIPTION
The Engine Control Module (ECM) uses the 5-volt reference 1 circuit as a sensor feed to the following sensors:
^ The accelerator pedal position Accelerator Pedal Position (APP) sensor 1
^ The accelerator pedal position APP sensor 3
^ The Fuel Rail Pressure (FRP) sensor

The ECM monitors the voltage on the 5-volt reference 1 circuit. If the voltage is out of tolerance the ECM will set Diagnostic Trouble Code (DTC) P1635.

CONDITIONS FOR RUNNING THE DTC
The ignition is ON.

CONDITIONS FOR SETTING THE DTC
^ The ECM 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 control module stores the DTC information into memory when the diagnostic runs and fails.
^ The Malfunction Indicator Lamp (MIL) will not illuminate.
^ The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
^ The driver information center, if equipped, may display a message.

CONDITIONS FOR CLEARING THE DTC
^ 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 non-emission related diagnostic.
^ Use a scan tool in order to clear the DTC.

TEST DESCRIPTION

Steps 1-5:

Steps 6-13:

The numbers below refer to the step numbers on the diagnostic table.
8. A short to the Transmission Control Module (TCM) Malfunction Indicator Lamp (MIL) request may not show up on the scan tool as skewed sensor readings. The TCM momentarily grounds the circuit as a test, and the test is just long enough to set this DTC.
11. This vehicle is equipped with a ECM which utilizes an electrically Erasable Programmable Read Only Memory (EEPROM). When the ECM is being replaced, the new ECM must be programmed.