The powertrain control module (PCM) uses the 5-volt reference A circuit as a sensor feed to the following sensors:
• | The fuel tank pressure (FTP) sensor |
• | The throttle position (TP) sensor |
• | The mass absolute pressure (MAP) sensor |
• | The exhaust gas recirculation (EGR) valve pintle position sensor |
• | The engine oil pressure 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.
The ignition is ON.
• | 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. |
• | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
• | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
• | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
• | 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 emission related diagnostic. |
• | Clear the MIL and the DTC with a scan tool. |
Important:: Be sure to inspect PCM and engine grounds for being secure and clean.
Check for the following conditions:
• | A poor connection at the PCM--Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. |
• | 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, 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 malfunction. |
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.
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No |
---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
2 |
Was a condition found? | -- | Go to Step 11 | Go to Step 3 |
3 |
Is voltage near the specified value indicated? | 5 V | Go to Step 5 | Go to Step 4 |
4 | Is voltage near the specified value indicated? | 0 V | Go to Step 6 | Go to Step 8 |
5 |
Is voltage near the specified value indicated? | 5 V | Go to Step 10 | Go to Step 9 |
6 |
Was a component replaced? | -- | Go to Step 11 | Go to Step 7 |
7 |
Was a condition found? | -- | Go to Step 11 | Go to Step 10 |
8 |
Was a condition found? | -- | Go to Step 11 | Go to Step 10 |
9 | Replace the EGR valve. Refer to Exhaust Gas Recirculation Valve Replacement . Is the action complete? | -- | Go to Step 11 | -- |
Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 11 | -- | |
11 |
Does the DTC run and pass? | -- | Go to Step 12 | Go to Step 2 |
12 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK |