P1635

Diagnostic Chart (Part 1 Of 2):

Diagnostic Chart (Part 2 Of 2):

Refer to Engine Controls Schematic A/C Pressure Switch, TP, MAP, ECT and IAT Sensors.

CIRCUIT DESCRIPTION
The PCM uses the 5 volt Reference A circuit as a sensor feed to the following sensors:
^ The Throttle Position (TP) sensor
^ The Manifold Absolute Pressure (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 PCM detects a voltage out of tolerance condition on the 5 volt Reference A circuit.
^ The above condition is present for more than 10 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM turns the MIL OFF after three consecutive drive trips during which the diagnostic runs and passes.
^ A last test failed, or the current DTC, clears when the diagnostic runs and passes.
^ A History DTC clears after forty consecutive warm-up cycles, if no other emission related diagnostic failures are reported.
^ Use a scan tool in order to clear the MIL diagnostic trouble code.
^ Interrupting the PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Powertrain Control Module (PCM) Description, Clearing Diagnostic Trouble Codes.

DIAGNOSTIC AIDS

NOTE: Refer to Connector Test Adapter kit J 35616-A Notice in Service Precautions.

IMPORTANT: Verify that the PCM grounds and the engine grounds are secure and clean.

Check for the following conditions:
^ A poor connection at the PCM.
Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connections.
^ A 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 and the engine not running while moving the connectors and the wiring harnesses related to the following sensors. A change in the MAP display will indicate the location of the malfunction.
- The TP sensor
- The MAP sensor
- The EGR valve

Reviewing the Failure 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.

If the problem is intermittent, refer to Intermittent Conditions. Intermittent Conditions

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
5. A component that does not affect the reference voltage when reconnected is considered passed. When the last component is reconnected, disconnect one of the 'passed' components to obtain the voltage measurement.
10. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read-only Memory (EEPROM). If the PCM is replaced, the new PCM must be programmed.