Circuit Description
The Electronic Suspension Control (ESC) module monitors a lift/dive signal at the Powertrain Control Module (PCM). Under normal conditions, the ESC module supplies a 5 volt reference voltage to the PCM. The PCM grounds this circuit when the vehicle is accelerating rapidly (LIFT) or braking hard (DIVE). When the lift/dive signal goes low (approximately 0 volts), the ESC module commands all four ESC dampers to a FIRM condition.
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
| • | The DTC is set if the ESC module does not detect the low-to-high transition on the lift/dive circuit within 31 seconds after the ignition is turned ON. |
| • | The fault is detected during three consecutive ignition cycles, or during the same ignition cycle after clearing the DTC with a scan tool. |
Action Taken When the DTC Sets
| • | The ESC lift/dive function will be disabled. |
| • | The vehicle will pitch more during a braking or wide open throttle condition. |
| • | 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 sees the low-to-high transition on the lift/dive signal from the PCM during a valid test period. The DTC will clear if the fault does not return after 50 consecutive ignition cycles. |
Diagnostic Aids
As part of the vehicle diagnostic system, the PCM toggles the lift/dive line within 31 seconds after the ignition is turned ON. This allows the ESC module to determine if the line is faulted or not. A retry is attempted every four minutes until successful.
An intermittent short to ground or an open in the Lift/Dive Signal circuit may cause a random firm/soft ride condition.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests for proper voltage in the chassis pitch signal circuit.
-
This step tests for communication between the PCM and the ESC module.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Refer to the appropriate RTD, RSS, or ESC Schematics | ||||
1 | Did you perform the Road Sensing Suspension Diagnostic System Check? | -- | Go to Step 2 | Go to Diagnostic System Check - RTD, RSS, or ESC |
Measure the voltage by probing from the chassis pitch signal circuit of the ESC module to a good ground. Does the voltage measure near the specified value? | 5 V | Go to Step 3 | Go to Step 4 | |
Does the voltage momentarily drop near the specified value within 31 seconds? | 1 V | Go to Diagnostic Aids | Go to Step 5 | |
4 | Does the voltage measure near the specified value? | B+ | Go to Step 8 | Go to Step 6 |
5 | Test the chassis pitch signal circuit for 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 11 | Go to Step 7 |
6 | 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 11 | Go to Step 9 |
7 | Inspect for poor connections at the harness connector of the PCM. 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 11 | Go to Step 10 |
8 | Repair the short to voltage in the chassis pitch signal circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 11 | -- |
9 |
Important: Perform the set up procedure for the ESC module. Replace the ESC module. Did you complete the replacement? | -- | Go to Step 11 | -- |
10 | Replace the PCM. Did you complete the replacement? | -- | Go to Step 11 | -- |
11 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
