For 1990-2009 cars
ABS Components
Antilock Brake System Schematics

### Circuit Description

Two-way serial communication is sent back and forth between the EBCM and the IPC. A message from the IPC is sent to the EBCM within seven seconds after ABS initialization. A serial communication failure does not allow the proper warning indicator commands to be sent back to the IPC.

### Diagnostic Aids

The following conditions may cause an intermittent malfunction:

• | A poor connection

• | Rubbed-through wire insulation

• | A broken wire inside the insulation

The scan tool Serial Data Link (SDL) monitor used in this diagnostic is within the body portion of the scan tool. This requires exiting from the chassis portion of the scan tool to the main menu and entering into the body portion of the scan tool menu and selecting SDL MONITOR.

With the SDL monitor (ABS to IPC mode), any message that is being transmitted on the serial data link can be observed.

Use the Lamp Test function of the Scan Tool in order to turn the indicator on while looking for an intermittent malfunction in the ABS warning indicator circuitry.

Thoroughly inspect any circuitry that may cause the intermittent complaint for the following conditions:

• | Backed out terminals

• | Improper mating

• | Broken locks

• | Improperly formed or damaged terminals

• | Poor terminal-to-wiring connections

• | Physical damage to the wiring harness

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Important: Zero J 39200 test leads before making any resistance measurements. Refer to J 39200 user's manual.
1 | Was the Diagnostic System Check performed? | -- | Go to Step 2 | Go to Diagnostic System Check
2 |

1. Turn the ignition switch to the OFF position.
2. Install a Scan Tool .
3. Turn the ignition switch to the RUN position.
4. Select Special Functions on the Scan Tool .
5. Select Lamp Test on the Scan Tool .
6. Use the Scan Tool in order to turn the amber ABS warning indicator on.

Did the amber ABS warning indicator turn on?

--

Go to Step 3

Go to Step 4

3 |

1. Select Special Functions on the Scan Tool .
2. Select Lamp Test on the Scan Tool .
3. Use the Scan Tool in order to flash the amber ABS warning indicator.

Did the amber ABS warning indicator flash?

--

Go to Step 7

Go to Step 4

4 | Inspect all of the connectors and the terminals for the following conditions:

• | Poor terminal contact

• | Evidence of corrosion

Is there evidence of poor terminal contact or corrosion?

--

Go to Step 5

Go to Step 6

5 | Replace all of the terminals that exhibit signs of poor terminal contact or corrosion. Is the repair complete? | -- | Go to Diagnostic System Check | --
6 | Repair the instrument panel cluster. Refer to Instrument Cluster: Analog Schematics in Instrument Panel, Gauges, and Console. Is the repair complete? | -- | Go to Diagnostic System Check | --
7 | The malfunction is intermittent or not present at this time. Refer to Diagnostic Aids for more information. Is the repair complete? | -- | Go to Diagnostic System Check | --