Circuit Description
The powertrain control module (PCM) uses the 5-volt reference circuit as a sensor feed to the following sensors:
| • | The boost sensor. |
| • | The crankshaft position (CKP) sensor. |
| • | The optical/fuel temperature sensor (CMP/High resolution). |
The ECM monitors the voltage on the 5-volt reference circuit. If the voltage is out of tolerance, the ECM will set DTC P1635.
Conditions for Running the DTC
The ignition is in the ON position.
Conditions for Setting the DTC
A 5-volt reference is less than 1 volt.
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. |
| • | Clear the DTC with a scan tool. |
Diagnostic Aids
During the time the failure is present, the setting of additional DTCs that share a 5-volt reference may also set.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step checks to confirm that a DTC is still present.
-
This step checks to determine if there is a 5-volt reference from the PCM.
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This step checks to determine if there is a short to ground in the reference circuit or a short to ground in the PCM.
-
This step determines if the short is being caused by one of the sensors on the engine or the short is in the wiring harness.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
Does the DTC reset? | -- | Go to Step 3 | Go to Step 5 | |
Does the voltage measure less than the specified value? | 4 V | Go to Step 4 | Go to Step 6 | |
Does the test lamp illuminate? | -- | Go to Step 7 | Go to Step 8 | |
5 | The DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids. If additional DTCs were stored refer to those tables. Are any additional DTCs stored? | -- | Go to Diagnostic Aids | |
6 | Replace the boost sensor. Refer to Boost Sensor Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
With the test lamp still probing the boost sensor 5-volt reference circuit at the PCM, disconnect each sensor, one at a time, that shares the 5-volt reference with the boost sensor. Does the test lamp turn OFF when one of the sensors is disconnected? | -- | Go to Step 9 | Go to Step 10 | |
8 |
Does the test lamp illuminate? | -- | Go to Step 10 | Go to Step 11 |
9 | Replace the sensor that caused the test lamp to turn OFF. Did you complete the replacement? | -- | Go to Step 12 | -- |
10 | Repair the short to ground in 5-volt reference circuit. Did you complete the repair? | -- | Go to Step 12 | -- |
11 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Does the DTC run and pass? | -- | Go to Step 13 | Go to Step 2 |
13 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
