Circuit Description
Spark retard is simultaneously controlled by the electronic brake control module (EBCM) and the powertrain control module (PCM). The PCM supplies a 12 volt pull up voltage. This voltage is monitored by the PCM, the EBCM requests spark retard by pulling the voltage low.
Conditions for Running the DTC
DTC 65 can be set anytime the ignition switch is in the ON position.
Conditions for Setting the DTC
The EBCM detects one of the following conditions in the spark retard circuitry:
| • | An open or high resistance |
| • | A short to ground |
| • | A short to voltage |
Action Taken When the DTC Sets
| • | The EBCM disables the traction control system for the remainder of the ignition cycle. |
| • | The TRAC OFF warning indicator turns ON. |
Conditions for Clearing the DTC
The condition responsible for setting the DTC no longer exists and the Scan Tool Clear DTCs function is used.
Diagnostic Aids
Thoroughly inspect the wiring and the connectors. An incomplete inspection of the wiring and the connectors may result in a misdiagnosis, causing a part replacement with the reappearance of the malfunction.
The following are possible causes of the malfunction:
| • | An open, high resistance, or a short in the spark retard circuit |
| • | An internal EBCM malfunction |
| • | An internal PCM malfunction |
If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Test Description
The numbers below refer to step numbers on the diagnostic table.
-
This step tests the voltage of spark retard circuit of the EBCM.
-
This step tests the spark retard circuit of the EBCM or a short to voltage.
-
This step tests the spark retard circuit of the EBCM or an open, high resistance or short to ground.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Antilock Brake System Schematics Connector End View Reference: Antilock Brake System Connector End Views | ||||
1 | Did you perform A Diagnostic System Check - ABS? | -- | Go to Step 2 | |
2 | Is DTC 73 set as a current DTC? | -- | Go to Step 3 | Go to Diagnostic Aids |
Does the voltage measure as specified? | Battery Voltage | Go to Step 4 | Go to Step 5 | |
Test the SPK retard circuit of the EBCM for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 6 | |
Test the SPK retard circuit of the EBCM for an open, high resistance or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 7 | |
6 | Replace the EBCM. Refer to Electronic Brake Control Module Replacement . Did you complete the replacement? | -- | Go to Step 8 | -- |
7 | Replace the powertrain control module (PCM). Refer to Powertrain Control Module Replacement in Engine Controls - 5.7L. Did you complete the replacement? | -- | Go to Step 8 | -- |
8 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
