For 1990-2009 cars
ABS Components
ABS Schematic References
Antilock Brake System Schematics
Data Link Connector Schematics
Power Distribution Schematics
Handling ESD Sensitive Parts Notice

### System Description

The diagnostic system check is an organized method of identifying any problems caused by a malfunction in either of the following systems:

• | The Antilock Brake System (ABS)

• | The Traction Control System (TCS)

The service technician must begin diagnosis of any ABS or ABS/TCS complaint with the diagnostic system check. The diagnostic system check directs the service technician to the next logical step in diagnosing the complaint.

The EBCM/EBTCM exchanges serial data through the connector C1 terminal A1. Connector C1 terminal A9 supplies the switched ignition voltage to the EBCM/EBTCM. Connector C1 terminal B12 supplies the battery voltage to the EBCM/EBTCM. Connector C2 terminal C supplies the switched battery voltage to the EBCM/EBTCM. Connector C2 Terminal D provides the ground for the EBCM/EBTCM.

### Diagnostic Process

Use the following ordered procedure when servicing the ABS/TCS.

Failure to use the following procedure may cause the loss of important diagnostic data. Failure to use the following procedure may lead to difficult and time-consuming diagnosis procedures.

1. Use the following procedure to perform a vehicle preliminary diagnosis inspection:

• | Inspect the brake master cylinder fluid reservoir:

- | Verify that the brake fluid level is correct.

- | Inspect the master cylinder for contamination.

• | Inspect the brake modulator for the following conditions:

- | Leaks

- | Wiring damage

• | Inspect the brake components of all four wheels:

- | Verify that no drag exists.

- | Verify that the brake apply operation is correct.

• | Inspect for worn or damaged wheel bearings.

• | Inspect the wheel speed sensors and the wheel speed sensor wirings:

- | Verify that all of the sensors solidly attach.

- | Inspect for wiring damage especially at vehicle attachment points.

2. Perform the Diagnostic System Check.

If any DTCs are displayed select DTC History.

2.1. | Determine which malfunction occurred most recently.

2.2. | Diagnose and repair the most recent malfunction first.

3. Determine if the following conditions exist:

• | No DTCs are present.

• | There are malfunctions in the mechanical components.

• | The failure is intermittent and cannot be reproduced.

4. If the above conditions exist attempt to reproduce the malfunction:

4.1. | Use the automatic snapshot feature of the Scan Tool while test driving the vehicle.

Perform normal acceleration, stopping and turning maneuvers during the test drive.

4.2. | If the test drive does not reproduce the malfunction perform an ABS stop:

• | Perform the stop on a low coefficient surface (such as gravel).

• | Perform the stop from a speed of 48-80 km/h (30-50 mph).

• | Trigger the snapshot mode on any ABS/TCS DTC while performing the stop.

4.3. | If the ABS stop does not reproduce the malfunction, use the enhanced diagnostic information in the DTC History in order to determine if further diagnosis is needed. This determination will be based on the frequency of failure.

5. Clear the ABS/TCS DTCs after all of the system malfunctions have been corrected.

### Diagnostic Aids

Communication with the EBCM/EBTCM is not possible when excessive resistance exists in the following components:

• | The ground

• | The power supply circuits

If communication with the EBCM/EBTCM is not possible, perform the following actions:

• | Verify that the EBCM/EBTCM ground connection is good.

• | Verify that no excessive resistance exists in any of the power supply circuits.

#### Diagnostic System Check

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Install the scan tool. Does the scan tool power up? | -- | Go to Step 3 | Go to Step 2
2 | Inspect the data link connector (DLC). Is the DLC connected correctly? | -- | Go to A Diagnostic System Check - Data Link Communications | --
3 |

1. Turn the ignition switch to the RUN position. Do not start the engine.
2. Select the ABS portion of the CHASSIS application on the scan tool.
3. Select DATA LIST.

Is data being received from the (EBCM)/(EBTCM)?

--

Go to Step 15

Go to Step 4

4 | Is the message "No Communication with Vehicle" displayed on the scan tool? | -- | Go to Step 5 | Go to A Diagnostic System Check - Data Link Communications
5 | Verify that the following EBCM/EBTCM components are connected:

• | The 24-way connector C1

• | The 8-way connector C2

• | The 8-way connector C3

Are the components connected correctly?

--

Go to Step 6

Connect components correctly and then go to Step 1

6 |

1. Turn the ignition switch to the OFF position.
2. Remove the ABS MDL BATT fuse (10A).
3. Use the J 39200 in order to measure resistance between the fuse terminals.

Is the resistance within the specified range?

0-2ohms

Go to Step 7

Go to Step 22

7 |

1. Install the ABS MDL BATT Fuse (10A).
2. Remove the fuse block ABS/TCS IGN Fuse (10A).
3. Use the J 39200 in order to measure the resistance between the fuse terminals.

Is the resistance within the specified range?

0-2ohms

Go to Step 8

Go to Step 23

8 |

1. Install the ABS/TCS IGN Fuse (10A).
2. Disconnect the 8-way EBCM/EBTCM connector C2.
3. Use the J 39200 in order to measure the resistance between connector C2 terminal D and ground.

Is the resistance within the specified range?

0-2ohms

Go to Step 9

Go to Step 28

9 |

1. Disconnect the 24-way EBCM/EBTCM connector C1.
2. Use the J 39200 in order to measure the voltage between connector C1 terminal B12 and ground.

Is the voltage within the specified voltage?

10.0-14.0 V

Go to Step 10

Go to Step 29

10 |

1. Turn the ignition switch to the RUN position (Do not start the engine).
2. Using the J 39200 , measure the voltage between the 24-way EBCM/EBTCM connector C1 terminal A9 and ground.

Is the voltage within the specified voltage?

10.0-14.0 V

Go to Step 11

Go to Step 30

11 |

1. Turn the ignition switch to the OFF position.
2. Disconnect the negative battery cable.
3. Use the J 39200 in order to measure the resistance between the 8-way EBCM/EBTCM connector C2 terminal D and the negative battery cable terminal.

Is the resistance within the specified range?

0-2ohms

Go to Step 12

Go to Step 31

12 |

1. Turn the ignition switch to the OFF position.
2. Use the J 39200 in order to measure the resistance between the 24-way EBCM/EBTCM connector C1 terminal A1 and the DLC terminal 9.

Is continuity present between the 24-way EBCM/EBTCM connector C1 terminal A1 and the DLC terminal 9?

--

Go to Step 13

Go to A Diagnostic System Check - Data Link Communications

13 | Use the J 39200 in order to measure the resistance between the 24-way EBCM/EBTCM connector C1 terminal A1 and ground. Is continuity present between the 24-way EBCM/EBTCM connector C1 terminal A1 and ground? | -- | Go to A Diagnostic System Check - Data Link Communications | Go to Step 14
14 |

1. Inspect the following components:

• | The 24-way EBCM/EBTCM connector C1

• | The 8-way EBCM/EBTCM connector C2

• | The 8-way EBCM/EBTCM connector C3

• | The negative battery cable

• | The positive

2. Inspect the components for the following conditions:

• | Poor terminal contact

• | Terminal corrosion

• | Damaged terminals

Are there signs of poor terminal contact, terminal corrosion, or damaged terminals?

--

Go to Step 32

Go to Step 33

15 |

1. Select view DTC's on the scan tool.
2. Check for stored DTC's in memory.

Does the scan tool display any current DTC's?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 16

16 |

1. Turn the ignition switch to the OFF position.
2. Remove the scan tool from the data link connector.
3. Cycle the ignition switch from the OFF to the ON position.
4. Do not start the engine.

Does the ABS Indicator come on then go OFF after three seconds (bulb check)?

--

Go to Step 18

Go to Step 17

17 | Does the ABS Indicator come ON and stay ON? | -- | Go to ABS Indicator Always On | Go to ABS Indicator Inoperative
18 | Is the vehicle TCS equipped? | -- | Go to Step 19 | Go to Step 21
19 |

1. Cycle the ignition switch from the OFF to the ON position.
2. Do not start the engine.

Does the TCS Indicator come on then go OFF after three seconds?

--

Go to Step 21

Go to Step 20

20 | Does the TCS Indicator come ON and stay ON? | -- | Go to Traction Control Indicator Always On | Go to Traction Control Indicator Inoperative
21 |

1. Reconnect the scan tool.
2. Turn the ignition switch to the ON position.
3. Select DTC HISTORY.
4. Inspect for any codes stored in memory.

Does the scan tool display any history DTC(s)?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 34

22 |

1. Turn the ignition switch to the OFF position.
2. Remove the ABS MDL BATT Fuse (10A).
3. Disconnect the 24-way EBCM/EBTCM connector C1.
4. Use the J 39200 to measure for continuity between the EBCM/EBTCM connector C1 terminal B12 and ground.
5. Wiggle wiring harness to simulate movement.

Is CKT 2940 shorted to ground?

--

Go to Step 26

Go to Step 24

23 |

1. Turn the ignition switch to the OFF position.
2. Remove the ABC/TCS IGN Fuse (10A).
3. Disconnect the 24-way EBCM/EBTCM connector C1.
4. Use the J 39200 in order to measure for continuity between the EBCM/EBTCM connector C1 terminal A9 and ground.
5. Wiggle wiring harness to simulate movement.

Is CKT 1639 shorted to ground?

--

Go to Step 27

Go to Step 25

24 |

1. Replace the EBCM/EBTCM.
2. Replace the ABS/TCS IGN fuse.

Is the repair complete?

--

Go to Step 1

--

25 |

1. Replace the EBCM/EBTCM.
2. Replace the ABS MDL BATT fuse.

Is the repair complete?

--

Go to Step 1

--

26 | Repair the short to ground in CKT 2940. Is the repair complete? | -- | Go to Step 1 | --
27 | Repair the short to ground in CKT 1639. Is the repair complete? | -- | Go to Step 1 | --
28 | Repair the open or high resistance in CKT 251. Is the repair complete? | -- | Go to Step 1 | --
29 | Repair the open or high resistance in CKT 2940. Is the repair complete? | -- | Go to Step 1 | --
30 | Repair the open or high resistance in CKT 1639. Is the repair complete? | -- | Go to Step 1 | --
31 | Repair the open or high resistance in any of the following components:

• | The negative battery cable

• | The negative battery cable terminals

• | The negative battery cable connections

Is the repair complete?

--

Go to Step 1

--

32 | Replace the terminals or the connectors that exhibit the following conditions:

• | Poor terminal contact

• | Terminal corrosion

• | Damaged terminals

Is the repair complete?

--

Go to Step 1

--

33 | Replace the EBCM/EBTCM. Is the repair complete? | -- | Go to Step 1 | --
34 | The system is functioning properly at this time. The malfunction may be intermittent or not present during testing. Is a concern still present? | -- | Go to Diagnostic Aids | System OK