Service Manual2006 Nubira-Lacetti ANTILOCK BRAKE SYSTEM

SECTION 4F

ANTILOCK BRAKE SYSTEM

Caution : Disconnect the negative battery cable before removing or installing any electrical unit or when a tool or equipment could easily come in contact with exposed electrical terminals. Disconnecting this cable will help prevent personal injury and damage to the vehicle. The ignition must also be in LOCK unless otherwise noted.

SPECIFICATIONS

Fastener Tightening Specifications

Application	N•m	Lb-Ft	Lb-In
ABS 5.3 Mounting Nuts	15	11	-
Brake Pipe Nuts	22	16	-
Front Wheel Speed Sensor Bolt	8	-	71

SPECIAL TOOLS

Special Tools Table

Scan Tool

SCHEMATIC AND ROUTING DIAGRAMS

Abs System Circuit (I)

Abs System Circuit (II)

EBCM Connector Face View

EBCM Connector

Pin	Color	Circuit
1	WHT	Right Rear Wheel Speed Sensor
2	-	Not Used
3	BRN	Right Rear Wheel Speed Sensor
4	WHT	Right Front Wheel Speed Sensor
5	GRY	Right Front Wheel Speed Sensor
6	BRN	Left Front Wheel Speed Sensor
7	LT BLU	Left Front Wheel Speed Sensor
8	RED	Left Rear Wheel Speed Sensor
9	BLK	Left Rear Wheel Speed Sensor
10	-	Not Used
11	DK BLU	Data Link Connector (DLC)
12	-	Not Used
13	-	Not Used
14	Lt BLU	Brake Lamp Switch
15	BRN	Switched Ignition
16	BLK	Motor Ground

Pin	Color	Circuit
17	RED	Battery
18	RED	Battery
19	BLK/WHT	Instrument Ground
20	LT GRN/BLK	ABS Warning Lamp
21	PPL/WHT	EBD Warning Lamp (Parking Brake Lamp)
22	DK GRN	TCS Warning Lamp
23	WHT/YEL	ECM
24	-	Not Used
25	LT GRN	ECM
26	-	Not Used
27	-	Not Used
28	-	Not Used
29	-	Not Used
30	-	Not Used
31	-	Not Used
SB	-	Shorting Bar

COMPONENT LOCATOR

ABS/EBD System Drive

(Left-Hand Drive Shown, Right-Hand Drive Similar)

Right Front Wheel Speed Sensor
Brake Master Cylinder
Master Cylinder Reservoir
Grommet
Right Front Wheel Speed Sensor Connector
Brake Fluid Level Switch Connector
Instrument Cluster
Connector C901
Right Rear Wheel Speed Sensor Connector
Right Rear Wheel Speed Sensor
Left Rear Wheel Speed Sensor
Left Rear Wheel Speed Sensor Connector
Body Wiring Harness
Connector C202
Connectors C110
EBCM Connector
Left Front Speed Sensor Connector
Grommet
Hydraulic Modulator with Attached EBCM
Connector C107
Left Front Wheel Speed Sensor

DIAGNOSIS

Diagnostic Circuit Check

The Diagnostic Circuit Check is an organized approach to identifying a problem created by an antilock brake system (ABS) malfunction. It must be the starting point for any ABS complaint diagnosis because it directs the service technician to the next logical step in diagnosing the complaint.

Diagnostic Process

Perform the following steps in order when servicing the ABS/EBD system. Failure to do so may result in the loss of important diagnostic data and may lead to difficulties and time-consuming diagnosis procedures.

Perform the tests of the table below.
Perform a road test if directed by the table.

Test drive the vehicle while using the snapshot feature of the scan tool.
Perform normal acceleration, stopping, and turning maneuvers.
If this does not reproduce the malfunction, perform an ABS stop on a low friction surface such as gravel.

Clear the diagnostic trouble codes (DTCs) after all system malfunctions have been corrected.

Diagnostic Circuit Check

Step	Action	Value(s)	Yes	No
1	Install the scan tool. Turn ignition switch to ON. Select the Data List mode. Is the scan tool receiving data from the electronic brake control module (EBCM) ?	-	Go to Step 2	Go to Step 6
2	Check the display. Are there any current DTCs displayed?	-	Refer to the applicable DTC table	Go to Step 3
3	Turn the ignition switch to LOCK for 10 seconds. Turn the ignition switch to ON and observe the ABS indicator. Does the indicator light for 4 seconds and then go off?	-	Go to Step 5	Go to Step 4
4	Check the ABS indicator. Did the ABS indicator turn on and stay on?	-	Go to "ABS Indicator Lamp Illuminated Constantly"	Go to "ABS Indicator Lamp Inoperative"
5	Turn the ignition switch to LOCK for 10 seconds. Turn the ignition switch to ON and observe the parking brake / EBD indicator. Does the indicator light for 4 seconds and then go off?	-	Go to Step 12	Go to "EBD System Indicator Lamp Inoperative"
6	Turn the ignition switch to LOCK. Disconnect the EBCM harness connector. Turn the ignition switch to ON. Use a digital voltmeter (DVM) to measure the voltage from ground to terminal 15, 17, and 18 of EBCM harness connector. Is the voltage within the specified value on each terminal?	11-14 v	Go to Step 7	Go to "Power Supply to Control Module, No DTCs Stored"
7	Turn the ignition switch to LOCK. Use a DVM to measure the resistance from the EBCM harness connector, terminals 16 and 19 to ground. Is the resistance equal to the specified value?	≈ 0 Ω	Go to Step 9	Go to Step 8
8	Repair the open in the circuit BLK and BLK/WHT that failed. Is the repair complete?	-	System OK	-
9	Use a DVM to measure the resistance between terminal 11 of the EBCM harness connector and terminal 12 of the Data Link Connector (DLC). Is the resistance below the specified value?	2 Ω	Go to Step 10	Go to Step 11
10	Replace the ABS unit assembly. Is the repair complete?	-	System OK	-
11	Repair the open or high resistance in circuit DK BLU between terminal 11 of the EBCM harness connector and terminal 12 of the DLC jack. Is the repair complete?	-	Go to Step 1	-
12	Perform the road test described above. Are any DTCs set?	-	Go to the table for the DTC	-

ABS Indicator Lamp Inoperative

Circuit Description

Battery voltage is supplied to the ABS warning lamp with the ignition switch in the ON or START positions. The warning lamp can be activated only by the ABS control module internally supplying ground to terminal 20 or by the shorting bar in the ABS module connector when it is disconnected from the module.

Diagnosis

This procedure checks for a problem in the wiring, a faulty ground, a voltage supply problem, a burned out indicator lamp, or a contact problem in a connector.

Cause(s)

A fuse has blown.
The indicator lamp has burned out.
There is a corroded or broken connector terminal.
There is a faulty ground connection.
There is a broken wire in a wiring harness.
The EBCM is faulty.

Test Description

The number(s) below refer to step(s) on the diagnostic table.

This test checks for any DTCs that may cause the ABS indicator lamp to be inoperative.
This test verifies an inoperative lamp condition.
This test checks for voltage on the lamp circuit.
This begins a series of tests of the circuit from the indicator lamp to the EBCM and ground.

This begins a series of tests of the voltage supply circuits that power the indicator lamp.

ABS Indicator Lamp Inoperative

Step	Action	Value(s)	Yes	No
1	Install the scan tool and check for any DTCs. Is any DTC set?	-	Go to the chart for the DTC	Go to Step 2
2	Turn the ignition switch to LOCK. Disconnect the scan tool. Turn the ignition switch to ON. Observe the ABS indicator lamp. Does the lamp illuminate for about 4 seconds, then turn off?	-	Go to "Intermittents and Poor Connections"	Go to Step 3
3	With the ignition still ON, observe the oil pressure lamp. Is the oil pressure lamp illuminated?	-	Go to Step 4	Go to Step 19
4	Turn the ignition switch to LOCK. Disconnect connector from the electronic brake control module (EBCM). Turn the ignition switch to ON. Does the ABS indicator illuminate?	-	Go to Step 5	Go to Step 8
5	Turn the ignition switch to LOCK. Examine terminals 19 and 20 at the EBCM connector on both the ABS wiring harness and on the EBCM. Is there a poor connection at any of these terminals?	-	Go to Step 6	Go to Step 7
6	Repair the faulty terminals or replace the ABS unit as required. Is the repair complete?	-	System OK	-
7	Replace the ABS unit. Is the repair complete?	-	System OK	-
8	Turn the ignition switch to LOCK. Disconnect the wire from the negative battery terminal. Measure the resistance between the negative battery wire, which is attached to ground, and the shorting bar in the EBCM connector. Does the resistance match the specified value?	0 Ω	Go to Step 10	Go to Step 9
9	Repair the open or high resistance in the circuit from EBCM connector, terminal 19 to ground G106. Is the repair complete?	-	System OK	-
10	Remove the I/P cluster. Remove and check the ABS indicator bulb. Is the bulb burned out?	-	Go to Step 11	Go to Step 12
11	Replace the ABS indicator bulb. Install the I/P cluster. Is the repair complete?	-	System OK	-
12	Check the continuity at the I/P cluster connector terminal A13. Does the ohmmeter show the specified value?	0 Ω	Go to Step 14	Go to Step 13
13	Repair the contact at the I/P cluster connector terminal A13. Is the repair complete?	-	System OK	-
14	Check the wiring harnesses and the connectors in circuit LT GRN/BLK from the I/P cluster terminal A13 to terminal 20 of the EBCM connector. Does the ohmmeter show the specified value?	∞	Go to Step 15	Go to Step 16
15	Repair the open or high resistance found. Is the repair complete?	-	System OK	-
16	Check for continuity between terminal 19 of the ABS connector and ground G106. Does the ground connection match the specified value?	0 Ω	Go to Step 17	Go to Step 18
17	Replace the ABS unit. Is the repair complete?	-	System OK	-
18	Repair the continuity problem between terminal 19 of the EBCM connector and ground G106. Is the repair complete?	-	System OK	-
19	Turn the ignition switch to LOCK. Check fuse F4 in the I/P fuse block. Is this fuse blown?	-	Go to Step 20	Go to Step 21
20	Replace fuse F4. Is the repair complete?	-	System OK	-
21	Check fuse EF5 in the engine fuse block. Is this fuse blown?	-	Go to Step 22	Go to Step 23
22	Replace fuse EF5. Is the repair complete?	-	System OK	-
23	Measure the voltage at terminal 2 of the ignition switch connector by backprobing. Does the voltage match the specified value?	11-14 v	Go to Step 25	Go to Step 24
24	Check circuit RED between terminal 4 of C105 at the engine fuse block and terminal 2 of the ignition switch for continuity. Repair any open or high resistance found. Is the repair complete?	-	System OK	-
25	Turn the ignition switch to ON. Backprobe terminal 4 (PNK) of the ignition switch connector. Does the voltage match the specified value?	11-14 v	Go to Step 27	Go to Step 26
26	Replace the ignition switch. Is the repair complete?	-	System OK	-
27	Turn the ignition switch to LOCK. Check circuit PNK from terminal 4 of the ignition switch to fuse F4 in the I/P fuse block. Does the ohmmeter show the specified value?	∞	Go to Step 28	Go to Step 29
28	Repair the open or the high resistance. Is the repair complete?	-	System OK	-
29	Remove the instrument cluster. Check circuit PNK from fuse F4 to terminal A19 of the I/P cluster connector B. Repair any open or high resistance found in a wiring harness, splice pack, or connector. Is the repair complete?	-	System OK	-

Power Supply to Control Module, No DTCs Stored

Circuit Description

Battery voltage is supplied to the electronic brake control module (EBCM) through fuse F11 in the I/P fuse block, to terminal 15 of the EBCM connector. The voltage is present when the ignition switch is in the ON or START position.

Diagnosis

This test checks for battery output, proper grounding, blown fuses, a faulty ignition switch, and problems in the circuitry.

Cause(s)

The battery is defective.
There is a defective ground connection.
A connector is damaged.
A wire is broken or shorted.
A fuse is blown.
The ignition switch is malfunctioning.

Fail Action

ABS action is disabled during the period of low voltage.

Test Description

The number(s) below refer to step(s) on the diagnostic table.

This step determines whether there is voltage at the battery and the high current source.
This step checks for voltage at the ignition 1 source.
This step begins the check for voltage at the EBCM end of the ABS harness.
This step checks for a defective ground connection.
This is a check for a defective EBCM connector.

Diagnostic Aids

It is very important to perform a thorough inspection of the wiring and the connectors. Failure to do so may result in misdiagnosis, causing part replacement with a reappearance of the malfunction.

Power Supply to Control Module, No DTCs Stored

Step	Action	Value(s)	Yes	No
1	Check the voltage at the battery. Is the voltage within the specified value?	11-14 v	Go to Step 3	Go to Step 2
2	Charge or replace the battery as required. Is the repair complete?	-	System OK	-
3	Check fuse EF2 in the engine fuse block. Is the fuse blown?	-	Go to Step 4	Go to Step 8
4	Replace fuse EF2. Turn the ignition to ON. Does the fuse blow again?	-	Go to Step 6	Go to Step 5
5	Check the ABS function. Is the repair complete?	-	System OK	-
6	Turn the ignition to OFF. Remove fuse EF2. Disconnect the ABS connector from the EBCM. Measure the resistance to ground at terminals 17 and 18. Does the ohmmeter show the specified value?	0 Ω	Go to Step 7	Go to Step 25
7	Repair the short to ground in circuit RED between terminal 1 of engine fuse block connector C107 and the ABS harness EBCM connector. Is the repair complete?	-	System OK	-
8	Check fuse EF5 in the engine fuse block. Is the fuse blown?	-	Go to Step 9	Go to Step 13
9	Replace fuse EF5. Turn the ignition to ON. Does the fuse blow again?	-	Go to Step 11	Go to Step 10
10	Check the ABS function. Is the repair complete?	-	System OK	-
11	Turn the ignition to OFF. Remove fuse EF5. Disconnect ABS connector from the EBCM. Measure the resistance to ground at terminal 15. Does the ohmmeter show the specified value?	0 Ω	Go to Step 12	Go to Step 25
12	Examine circuit RED between terminal 4 of engine fuse block connector C105 and terminal 2 of the ignition switch. Examine circuit PNK from terminal 4 of the ignition switch to fuse F11 in the I/P fuse block. Examine circuit PNK from fuse F11 in the I/P fuse block to terminal 15 of the ABS EBCM connector. Repair any short to ground found in the wiring or the ignition switch. Is the repair complete?	-	System OK	-
13	Check fuse F11 in the I/P fuse block. Is the fuse blown?	-	Go to Step 14	Go to Step 18
14	Replace fuse F11. Turn the ignition to ON. Does the fuse blow again?	-	Go to Step 16	Go to Step 15
15	Check the ABS function. Is the repair complete?	-	System OK	-
16	Turn the ignition to OFF. Remove fuse F11. Disconnect ABS connector from the EBCM. Measure the resistance to ground at terminal 15. Does the ohmmeter show the specified value?	0 Ω	Go to Step 17	Go to Step 25
17	Repair the short to ground in circuit PNK fuse F11 of the I/P fuse block and terminal 15 of the ABS harness EBCM connector. Is the repair complete?	-	System OK	-
18	Disconnect the EBCM connector from the EBCM. Turn the ignition to ON. Check for the presence of battery voltage between ground and terminal 17, and between ground and terminal 18. Is the voltage within the specified value?	11-14 v	Go to Step 20	Go to Step 19
19	Turn the ignition switch to OFF. Trace the RED wires between terminals 17 and 18 of the EBCM connector to terminal 1 of connector C107 at the engine fuse block. Repair the open in this circuit. Is the repair complete?	-	System OK	-
20	Check the voltage between ground and terminal 15 of the EBCM connector. Is the voltage within the specified value?	11-14 v	Go to Step 22	Go to Step 21
21	Turn the ignition switch to OFF. Trace circuit PNK between terminal 15 of the ABS harness EBCM connector to fuse F11 in the I/P fuse block. Trace circuit PNK from fuse F11 of the I/P fuse block to terminal 4 (IG1) of the ignition switch. Trace circuit RED from terminal 2 (B1) of the ignition switch to terminal 4 of connector C105 at the engine fuse block and to fuse EF5. Repair the open in the wiring or possibly bad connector terminal, defective ignition switch, or blown fuse EF5. Is the repair complete?	-	System OK	-
22	Turn the ignition to OFF. Check the resistance between ground and terminals 19 and 16 of the EBCM connector. Does the ohmmeter show the specified value?	0 Ω	Go to Step 23	Go to Step 26
23	Examine terminals 15, 19, 17, 18, and 16 of the EBCM connector. Is there a defective terminal?	-	Go to Step 24	Go to Step 25
24	Repair the defective terminal or replace the connector or wiring harness as required. Is the repair complete?	-	System OK	-
25	Replace the ABS unit. Is the repair complete?	-	System OK	-
26	Repair the defective ground connection. Is the repair complete?	-	System OK	-

ABS Indicator Lamp Illuminated Continuously, No DTCs Stored

Circuit Description

Battery voltage is supplied to the ABS warning lamp with the ignition switch in the ON or START position. The warning lamp should be activated only by the ABS control module internally supplying ground to terminal 20.

Diagnosis

This procedure checks for a short to ground in the wiring or a defective electronic brake control module (EBCM).

Cause(s)

There is a short to ground in the circuit between the cluster terminal A13 and the EBCM terminal 20.
The EBCM is faulty.

Test Description

The number(s) below refer to step(s) on the diagnostic table.

This step determines whether the EBCM is faulty.
This begins a search for a short to ground in the circuit between the ABS indicator lamp and the EBCM.

ABS Indicator Lamp Illuminated Continuously, No DTCs Stored

Step	Action	Value(s)	Yes	No
1	Check the EBCM connector. Is it connected properly?	-	Go to Step 3	Go to Step 2
2	Connect the EBCM connector. Is the repair complete?	-	System OK	-
3	Disconnect the EBCM connector. Turn the ignition switch to ON. Use an insulated tool to push the shorting bar in the connector away from terminal 20. Does the ABS indicator lamp go out?	-	Go to Step 4	Go to Step 5
4	Replace the ABS unit. Is the repair complete?	-	System OK	-
5	Turn the ignition switch to OFF. Connect the EBCM connector. Disconnect connector C110. Turn the ignition switch to ON. Does the ABS indicator lamp illuminate?	-	Go to Step 7	Go to Step 6
6	Repair the short to ground in circuit LT GRN between connector C110 and the EBCM connector. Is the repair complete?	-	System OK	-
7	Repair the short to ground in circuit LT GRN between I/P cluster connector A13 and connector C110. Is the repair complete?	-	System OK	-

Electronic Brake-Force Distribution (EBD) System Indicator Lamp Inoperative

Circuit Description

Battery voltage is supplied to the EBD warning lamp with the ignition switch in the ON or START position. The warning lamp can be activated only by the ABS control module internally supplying ground to terminal 21.

Diagnosis

This procedure checks for a problem in the wiring, a faulty ground, a voltage supply problem, a burned out indicator lamp, or a contact problem in a connector.

Cause(s)

A fuse has blown.
The indicator lamp has burned out.
There is a corroded or broken connector terminal.
There is a faulty ground connection.
There is a broken wire in a wiring harness.
The EBCM is faulty.

Test Description

The number(s) below refer to step(s) on the diagnostic table.

This test checks for any DTCs that may cause the EBD indicator lamp to be inoperative.
This test verifies an inoperative lamp condition.
This test checks for voltage on the lamp circuit.
This begins a series of tests of the circuit from the indicator lamp to the EBCM and ground.
This begins a series of tests of the voltage supply circuits that power the indicator lamp.

EBD System Indicator Lamp Inoperative

Step	Action	Value(s)	Yes	No
1	Install the scan tool and check for any DTCs. Is any DTC set?	-	Go to the chart for the DTC	Go to Step 2
2	Turn the ignition switch to LOCK. Disconnect the scan tool. Release the parking brake fully. Push the brake pedal. Turn the ignition switch to ON. Observe the EBD indicator lamp. Does the lamp illuminate for about 4 seconds, then turn off?	-	Go to "Intermittents and Poor Connections"	Go to Step 3
3	With the ignition still ON, observe the oil pressure lamp. Is the oil pressure lamp illuminated?	-	Go to Step 4	Go to Step 19
4	Turn the ignition switch to LOCK. Disconnect connector from the EBCM. Connect a jumper from terminal 21 to the grounding bar in the connector. Turn the ignition switch to ON. Does the EBD indicator illuminate?	-	Go to Step 5	Go to Step 8
5	Turn the ignition switch to LOCK. Examine terminals 19 and 21 at the EBCM connector on both the ABS wiring harness and on the EBCM. Is there a poor connection at any of these terminals?	-	Go to Step 6	Go to Step 7
6	Repair the faulty terminals or replace the ABS unit as required. Is the repair complete?	-	System OK	-
7	Replace the ABS unit. Is the repair complete?	-	System OK	-
8	Turn the ignition switch to LOCK. Disconnect the wire from the negative battery terminal. Measure the resistance between the negative battery wire, which is attached to ground, and the shorting bar in the EBCM connector. Does the resistance match the specified value?	0 Ω	Go to Step 10	Go to Step 9
9	Repair the open or high resistance in the circuit from EBCM connector, terminal 19 to ground G106. Is the repair complete?	-	System OK	-
10	Remove the I/P cluster. Remove and check the EBD indicator bulb. Is the bulb burned out?	-	Go to Step 11	Go to Step 12
11	Replace the EBD indicator bulb. Install the I/P cluster. Is the repair complete?	-	System OK	-
12	Check the continuity at the I/P cluster connector terminal A1. Does the ohmmeter show the specified value?	0 Ω	Go to Step 14	Go to Step 13
13	Repair the contact at the I/P cluster connector terminal A1. Is the repair complete?	-	System OK	-
14	Check the wiring harnesses and connectors in circuit PPL/WHT from the I/P cluster terminal A1 to terminal 21 of the EBCM connector. Does the ohmmeter show the specified value?	∞	Go to Step 15	Go to Step 16
15	Repair the open or high resistance found. Is the repair complete?	-	System OK	-
16	Check for continuity between terminal 19 of the ABS connector and ground G106. Does the ground connection match the specified value?	0 Ω	Go to Step 17	Go to Step 18
17	Replace the ABS unit. Is the repair complete?	-	System OK	-
18	Repair the continuity problem between terminal 19 of the EBCM connector and ground G106. Is the repair complete?	-	System OK	-
19	Turn the ignition switch to LOCK. Check fuse F4 in the I/P fuse block. Is this fuse blown?	-	Go to Step 20	Go to Step 21
20	Replace fuse F4. Is the repair complete?	-	System OK	-
21	Check fuse EF5 in the engine fuse block. Is this fuse blown?	-	Go to Step 22	Go to Step 23
22	Replace fuse EF5. Is the repair complete?	-	System OK	-
23	Measure the voltage at terminal 2 of the ignition switch connector by backprobing. Is the voltage within the specified value?	11-14 v	Go to Step 25	Go to Step 24
24	Check circuit RED between terminal 4 of C105 at the engine fuse block and terminal 2 of the ignition switch for continuity. Repair any open or high resistance found. Is the repair complete?	-	System OK	-
25	Turn the ignition switch to ON. Backprobe terminal 4 (PNK) of the ignition switch connector. Is the voltage within the specified value?	11-14 v	Go to Step 27	Go to Step 26
26	Replace the ignition switch. Is the repair complete?	-	System OK	-
27	Turn the ignition switch to LOCK. Check circuit PNK from terminal 4 of the ignition switch to fuse F4 in the I/P fuse block. Does the ohmmeter show the specified value?	∞	Go to Step 28	Go to Step 29
28	Repair the open or the high resistance. Is the repair complete?	-	System OK	-
29	Remove the instrument cluster. Check circuit PNK from fuse F4 to terminal B15 or A19 of the I/P cluster connector A. Repair any open or high resistance found in a wiring harness, splice pack, or connector. Is the repair complete?	-	System OK	-

Self-Diagnostics

Important : The electronic brake control module (EBCM) turns the valve relay off when a diagnostic trouble code (DTC) is set. The scan tool will indicate that the valve relay is off when it is used to monitor the data list. This is normal and should not be considered a malfunction.

Important : For safety reasons it is recommended that the vehicle not be driven with test equipment connected. Exception : for testing of wheel speeds provided the test regulations are met.

The EBCM performs system self-diagnostics and can detect and often isolate system malfunctions. When it detects a malfunction, the EBCM sets a DTC that represents the malfunction, turns ON the ABS and/or the EBD indicators in most instances, and may disable the ABS and/or the EBD functions as necessary for the duration of the ignition cycle.

Once each ignition cycle, the EBCM performs an automatic test when the vehicle speed > 6 km/h and the brake pedal is not actuated or when the vehicle speed > 15 km/h and the brake pedal is actuated. In the course of this test, the system cycles each valve solenoid and the pump motor, along with the necessary relays, to check component operation. If the EBCM detects any malfunctions, it will set a DTC as described above.

Displaying DTCs

Tools Required

Scan Tool

DTCs can be read through the use of the scan tool.

Clearing DTCs

Tools Required

Scan Tool

The diagnostic trouble codes (DTCs) in the electronic brake control module (EBCM) memory are erased:

Use the scan tool "Clear DTCs" selection.

The method is detailed below. Be sure to verify proper system operation and absence of DTCs when the clearing procedure is completed.

The EBCM will not permit DTC clearing until all DTCs have been displayed. Also, DTCs cannot be cleared by disconnecting the EBCM, disconnecting the battery cables, or turning the ignition switch to LOCK.

Scan Tool Method

The scan tool can clear ABS system DTCs using the mass storage cartridge.

Install the scan tool and the mass storage cartridge.
Select "Fault Memory."
Select "Clear Fault Memory."

Clearing the fault memory cannot reset a valve relay which was shut down when the fault was recognized. Changes are possible only after the fault has been eliminated and the next ignition cycle has begun.

Intermittents and Poor Connections

As with most electronic systems, intermittent malfunctions may be difficult to diagnose accurately. The following is a method to try to isolate an intermittent malfunction, especially in wheel speed circuitry.

If an ABS malfunction occurs, the ABS indicator will illuminate during the ignition cycle in which the malfunction was detected. If it is an intermittent problem which seems to have corrected itself (ABS indicator off), a history DTC will be stored. Also stored will be the history data of the DTC at the time the malfunction occurred. Use the scan tool modular diagnostic system to read ABS history data.

Most intermittents are caused by faulty electrical connections or wiring, although a sticking relay or solenoid can occasionally be at fault.