For 1990-2009 cars

### Circuit Description

The EBCM/EBTCM Diagnostic System Check is an organized approach to identify problems associated with the EBCM/EBTCM. This check must be the starting point for any EBCM/EBTCM complaint, and will direct you to the next logical step in diagnosing the complaint. The EBCM/EBTCM is a very reliable component and is not likely the cause of the malfunction. Most system complaints are linked to faulty wiring, connectors, and occasionally to components. Understanding the ABS system and using the tables correctly will reduce diagnostic time and prevent unnecessary parts replacement.

### Diagnostic Aids

An intermittent failure in the electronic system may be very difficult to detect and to accurately diagnose. The EBCM/EBTCM test for different malfunctions under different vehicle conditions. For this reason, a thorough test drive is often needed in order to repeat a malfunction. If the system malfunction is not repeated during the test drive, a good description of the complaint may be very useful in locating an intermittent malfunction. Faulty electrical connections or wiring causes most intermitting problems. When an intermitting condition is suspected, check the suspected circuits for the following conditions:

• | Poor mating of connector halves or backed out terminals

• | Improperly formed or damaged terminals

• | Wire chafing

• | Poor wire to terminal connections

• | Dirty or corroded terminals

• | Damage to connector bodies

If the DTC is a history DTC, the problem may be intermittent. Perform the tests shown while moving related wiring and connectors. This can often cause the malfunction to occur. Perform a thorough inspection of all related wiring and connectors pertaining to the history DTC stored. Refer to General Electrical Diagnosis in Wiring Systems.

Important: Any battery disconnect or removal of battery positive voltage from the EBCM/EBTCM will cause a DTC C1255e2 to be set as a history code. This DTC should be ignored and cleared immediately.

#### ABS Diagnostic System Check

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 |

1. Reconnect all previously disconnected components.
2. Cycle the ignition switch from the OFF to RUN position, engine off.
3. Plug a scan tool into the Diagnostic Link Connector (DLC).

Does the scan tool communicate with the EBCM/EBTCM?

--

Go to Step 3

Go to Step 2

2 | Does the scan tool communicate with other modules on the UART serial data line? | -- | Go to No Communication with Electronic Brake Control Module/Electronic Brake and Traction Control Module | Go to Data Link Communications System Check in Wiring Systems
3 |

1. With the scan tool in ABS/TCS Special Functions run the AUTOMATED test.
2. With the scan tool read ABS/TCS DTC(s).

Are there any current Diagnostic Trouble Codes?

--

Go to Diagnostic Trouble Code (DTC) List for Applicable DTC Table

Go to Step 4

4 | Cycle the ignition switch from the OFF to RUN position, engine off. Does the ABS Indicator turn on then turn off after several seconds? | -- | Go to Step 5 | Go to Step 7
5 | Is this vehicle equipped with Traction Control? | -- | Go to Step 6 | Go to Step 12
6 | Cycle the ignition switch from the OFF to RUN position, engine off. Does the Traction Off Indicator turn on then turn off after several seconds? | -- | Go to Step 8 | Go to Step 9
7 | Does the ABS Indicator stay on? | -- | Go to ABS Indicator Always On | Go to ABS Indicator Inoperative
8 | Is the vehicle an Oldsmobile? | -- | Go to Step 10 | Go to Step 12
9 | Does the Traction Off Indicator stay on? | -- | Go to Traction Off Indicator Always On | Go to Traction Off Indicator Inoperative
10 | Cycle the ignition switch from the OFF to RUN position, engine Off. Does the Traction Active Indicator turn on then turn off after several seconds? | -- | Go to Step 12 | Go to Step 11
11 | Does the Traction Active Indicator stay on? | -- | Go to Traction Active Indicator Always On | Go to Traction Active Indicator Inoperative
12 | Are there any history DTC(s)? | -- | Go to Step 13 | System OK
13 |

1. Refer to the appropriate DTC table for the history DTC.
2. Read the diagnostic aids, and the conditions for setting the DTC.
3. Carefully drive the vehicle above 24 Km/h (15 mph) for several minutes, while monitoring a scan tool.

Did the history DTC set as a current DTC while the vehicle was being driven?

--

Go to Diagnostic Trouble Code (DTC) List for Applicable DTC Table

System OK