Circuit Description
The electronic suspension control (ESC) module estimates the road surface and communicates that information to the Electronic Brake Control module (EBCM). The ESC module provides a Pulse Width Modulation (PWM) signal to the EBCM through the left and right normal force signal circuits. The ESC module sends each normal force value twice to the EBCM. The possible values of the PWM duty cycle are 20%, 40%, 60% and 80%, with the valid range from 10-90%. The EBCM uses this information to provide improved rough-road braking performance.
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
DTC C0635 or C0640
The DTC is set when the ESC module measures a feedback voltage less than a preset value during 5 consecutive normal force signal output OFF state tests.
DTC C0638 or C0643
The DTC is set when the ESC module measures a feedback voltage greater than a preset value during 5 consecutive normal force signal output ON state tests.
DTC C1252 or C1253
The DTC is set if one of the following conditions is present for 5 seconds of any 10 second period:
| • | The PWM duty cycle is outside the valid range of 10-90%. |
| • | The PWM duty cycle value does not match either the previous or the next PWM duty cycle value. |
Action Taken When the DTC Sets
| • | Both the left and right normal force outputs are set to default output states. |
| • | The EBCM disables the rough road detection function for the duration of the ignition cycle. |
| • | The SERVICE SUSPENSION SYS message will be displayed. |
Conditions for Clearing the MIL/DTC
| • | The scan tool can be used to clear the DTC. |
| • | The DTC is saved as history when the ESC module no longer sees an out of range feedback voltage during 5 consecutive normal force OFF states. The DTC will clear if the fault does not return after 50 consecutive ignition cycles. |
Diagnostic Aids
| • | The DTC may be caused by an open or a short in the normal force signal circuit. Refer to Circuit Testing in Wiring Systems. |
| • | The DTC may be caused by a poor connection at the EBCM or ESC module connectors. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests for a valid duty cycle in the normal force signal circuit.
-
This step tests for normal voltage in the normal force signal circuit.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Suspension Controls Schematics | ||||
1 | Did you perform the Electronic Suspension Control Diagnostic System Check? | -- | Go to Step 2 | Go to Diagnostic System Check - Electronic Suspension Control |
Does the scan tool display within the specified range? | 10-90% | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 | |
Does the voltage measure greater than the specified value? | B+ | Go to Step 5 | Go to Step 4 | |
4 | Test the normal force signal circuit for high resistance, a short to ground, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 6 |
5 | Test the normal force signal circuit 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 10 | Go to Step 7 |
6 | Inspect for poor connections at the harness connector of the Electronic Brake Control module (EBCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9 |
7 | Inspect for poor connections at the harness connector of the ESC module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 8 |
8 | Replace the EBCM. Refer to Electronic Brake Control Module Replacement in Antilock Brake System. Did you complete the replacement? | -- | Go to Step 10 | -- |
9 | Replace the ESC module. Refer to Electronic Suspension Control Module Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- |
10 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
