Circuit Description
The 5 inputs to the electronic brake control module (EBCM), which are used solely for vehicle stability enhancement, are the longitudinal accelerometer, lateral accelerometer, yaw rate sensor, master cylinder pressure sensor, and the steering wheel position sensor. The EBCM must detect valid inputs from all 5 sources during the initialization period in order to enable the vehicle stability enhancement system (VSES). Initialization must occur during the first 3 000 meters of vehicle travel or 1 000 meters of straight vehicle travel. If initialization cannot be achieved during this time period, the VSES remains inactive and the stability system not ready indicator is illuminated. The EBCM does not attempt to reinitialize until the next ignition cycle. One or more DTCs often set, shortly after an unsuccessful initialization attempt, indicating the root cause of the failure. If this occurs, the stability system not ready indicator is no longer illuminated. The stability system caution indicator is illuminated instead.
Diagnostic Aids
If the customer concern is that the stability system disabled message is displayed intermittently, communicate with the customer to determine what driving conditions are being experienced at the time the message is displayed. The EBCM may be unable to successfully initialize the system during operation on very winding roads. Initialization may also be unsuccessful if pressure is continuously applied to the brake pedal during the initialization period.
If the message is displayed due to any of the above conditions, no diagnosis or repair of the VSES is required.
Step | Action | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |||||||||
2 |
Is the stability system not ready indicator illuminated? | Go to Step 3 | Go to Diagnostic Aids | ||||||||
3 | Use the scan tool to display vehicle stability enhancement system (VSES) History DTCs. Are any of the following DTCs stored in History?
| Go to Step 4 | Go to Step 5 | ||||||||
4 | Operate the vehicle within the conditions for running any history DTCs which may be the cause of unsuccessful initialization. Do any of the DTCs listed in step 4 set as a Current DTC? | Go to Step 5 | |||||||||
5 |
Do the Digital SWPS Phase A and the Digital SWPS Phase B parameters both transition from Low to High as the steering wheel is rotated? | Go to Step 1 | Go to Step 6 | ||||||||
6 |
Does the scan tool display that both parameters are low? | Go to Step 7 | Go to Step 13 | ||||||||
7 |
Does the scan tool display the Digital SWPS Phase A signal as being High? | Go to Step 10 | Go to Step 8 | ||||||||
8 | Test the battery positive voltage circuit for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 18 | Go to Step 9 | ||||||||
9 | Test the steering wheel position signal A circuit for an open, a high resistance, or short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 18 | Go to Step 15 | ||||||||
10 |
Does the scan tool display the Digital SWPS Phase B signal as being High? | Go to Step 12 | Go to Step 11 | ||||||||
11 | Test the steering wheel position signal B circuit for an open, a high resistance, or short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 18 | Go to Step 15 | ||||||||
12 | Test each ground circuit to the steering wheel position sensor for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 18 | Go to Step 14 | ||||||||
13 | Test each steering wheel position sensor signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 18 | Go to Step 15 | ||||||||
14 | Inspect for poor connections at the harness connector of the steering wheel position sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 18 | Go to Step 16 | ||||||||
15 | 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 . Did you find and correct the condition? | Go to Step 18 | Go to Step 17 | ||||||||
16 | Replace the steering wheel position sensor. Refer to Steering Wheel Position Sensor or Steering Shaft Lower Bearing Replacement . Did you complete the replacement? | Go to Step 18 | -- | ||||||||
17 |
Important: Following the EBCM replacement, perform the set-up procedure for the EBCM and use the scan tool to perform the Tire Size Calibration procedure. Replace the EBCM. Refer to Electronic Brake Control Module Replacement . Did you complete the replacement? | Go to Step 18 | -- | ||||||||
18 |
Is the stability system not ready indicator illuminated? | Go to Step 3 | System OK |
