Circuit Description
For vehicles equipped with a U23 or a UH8 instrument cluster, the TRACTION OFF indicator is controlled by the EBCM/EBTCM via serial data UART.
For vehicles equipped with a UB3, a U2F, or a U50 instrument cluster, the TRACTION OFF indicator is controlled by the EBCM/EBTCM via the brake lamp driver module. The instrument cluster or remote indicator bank supplies voltage to the indicator. The brake lamp driver module acts as an inverter. When the EBCM/EBTCM supplies ground to the brake lamp driver module, the indicator remains OFF. When the EBCM/EBTCM removes ground from the brake lamp driver module, the brake lamp driver module supplies ground to the TRACTION OFF indicator.
Diagnostic Aids
| • | Buick uses the U23 and the UB3 instrument clusters. |
| • | Oldsmobile uses the UH8 instrument cluster. |
| • | Pontiac uses the UB3, the U2F, and the U50 instrument clusters. |
| • | It is very important that a thorough inspection of the wiring and connectors be performed. Failure to carefully and fully inspect wiring and connectors may result in misdiagnosis, causing part replacement with reappearance of the malfunction. |
| • | An intermittent malfunction can be caused by poor connections, broken insulation, or a wire that is broken inside the insulation. |
| • | If an intermittent malfunction exists, refer to Intermittents and Poor Connections Diagnosis in Wiring Systems. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step checks if the instrument cluster is controlled by serial data or hard wired through the brake lamp to the EBCM/EBTCM.
-
This step checks if the instrument cluster can turn the TRACTION OFF indicator on.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the ABS Diagnostic System Check? | -- | Go to Step 2 | |
Is this vehicle equipped with a U23 or a UH8 Instrument cluster? | -- | Go to Step 3 | Go to Step 7 | |
3 |
Does the switch status change as the TCS switch is pressed and released? | -- | Go to Step 4 | Go to Step 24 |
Use the scan tool in ABS/TCS Special Functions in order to command the TRACTION OFF indicator on. Does the indicator turn on? | -- | Go to Step 5 | Go to Step 6 | |
5 | Replace the EBCM/EBTCM. Refer to Electronic Brake Control Module Replacement . Did you complete the repair? | -- | -- | |
6 | Inspect the instrument cluster. Refer to Diagnostic System Check - Instrument Cluster in Instrument Panel, Gauges and Console. Is the diagnosis complete? | -- | -- | |
7 |
Does the switch status change as the TCS switch is pressed and released? | -- | Go to Step 8 | Go to Step 24 |
8 |
Does the TRACTION OFF indicator turn on? | -- | Go to Step 5 | Go to Step 9 |
9 |
Is the fuse OK? | -- | Go to Step 10 | Go to Step 11 |
10 |
Is the voltage within the specified range? | Battery Voltage | Go to Step 12 | Go to Wiring Repairs in Wiring Systems |
11 |
Is the resistance within the specified range? | OL (infinite) | Go to Step 15 | Go to Step 14 |
12 |
Is the voltage within the specified range? | Battery Voltage | Go to Step 13 | Go to Step 23 |
13 | Use the J 39200 DMM in order to measure the voltage to ground at terminal A of the brake lamp driver module harness connector. Is the voltage within the specified range? | Battery Voltage | Go to Step 16 | Go to Step 17 |
14 | Repair a short to ground in CKT 39 (PNK). Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |
15 |
Is the fuse OK? | -- | Go to Step 21 | |
16 |
Is the resistance less than the specified value? | 5 ohms | Go to Step 18 | Go to Step 21 |
17 |
Is the resistance less than the specified value? | 5 ohms | Go to Step 6 | Go to Step 22 |
18 |
Is the resistance within the specified range? | OL (infinite) | Go to Step 19 | Go to Step 20 |
19 | Replace the brake lamp driver module. Refer to Lamp Driver Module Replacement . Did you complete the repair? | -- | -- | |
20 | Repair a short to ground in CKT 1572 (PPL/WHT). Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |
21 | Repair an open in CKT 1250 (BLK). Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |
22 | Repair an open or high resistance in CKT 1660 (DK BLU). Refer to Wiring Repairs . Did you complete the repair? | -- | -- | |
23 | Repair an open or high resistance in CKT 39 (PNK). Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |
24 |
Is the resistance less than the specified value? | 5 ohms | Go to Step 5 | Go to Step 25 |
25 |
Is the resistance less than the specified value? | 5 ohms | Go to Step 27 | Go to Step 26 |
26 | Repair an open in CKT 1571 (BRN/WHT). Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |
27 | Use the J 39200 DMM in order to measure the resistance between CKT 251 (BLK/WHT) of the TCS switch harness connector and a good ground. Is the resistance less than the specified value? | 5 ohms | Go to Step 28 | Go to Step 29 |
28 | Replace the TCS switch. Refer to Instrument Panel, Gauges and Console. Did you complete the repair? | -- | -- | |
29 | Repair an open in CKT 251 (BLK/WHT). Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- |
