Normal Operation

The brake warning light is used to indicate low brake fluid level (base brake system concern) or a parking brake that is not fully released. The instrument cluster is hardwired to the parking brake switch through circuit (GY/L) for parking brake status. The instrument cluster is hardwired to the anti-lock brake system (ABS) module through the electronic brake distribution (EBD) line, circuit (G/V), for brake fluid level concerns. When the parking brake is applied, the instrument cluster receives a ground and turns on the brake warning indicator. When brake fluid is low or the ABS module detects a base brake system concern, the ABS module sends the instrument cluster a signal through the EBD line and the instrument cluster turns on the brake warning indicator. If the instrument cluster detects fault condition in either the base brake system (low brake fluid level) or ABS, both the brake and ABS warning indicators are turned on.

This pinpoint test is intended to diagnose the following:

Wiring, terminals or connectors
Parking brake switch
ABS module
Instrument cluster
CAUTION:
- Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.

BRAKE WARNING INDICATOR PINPOINT TEST 28

PINPOINT TEST 28		THE BRAKE WARNING INDICATOR IS ALWAYS ON
STEP	INSPECTION		ACTION
1	CARRY OUT THE INSTRUMENT CLUSTER INDICATOR LAMP CONTROL ACTIVE COMMAND USING THE SCAN TOOL Key in ON position. Enter the following diagnostic mode on the scan tool: Instrument Cluster DataLogger Select the instrument cluster brake warning indicator (BRK_LAMP) active command. Command the brake warning indicator on then off again. Observe the brake warning indicator. Does the brake warning indicator turn off when commanded off?	Yes	Go to next step.
1		No	Go to step 9.
2	RETRIEVE THE RECORDED DTCs FROM BOTH THE CONTINUOUS AND ON-DEMAND ABS MODULE SELF-TESTS Use the recorded ABS module DTCs from the continuous and on-demand self-tests. Are any DTCs present?	Yes	See ANTI-LOCK BRAKE SYSTEM (ABS) MODULE DIAGNOSTIC TROUBLE CODE (DTC) INDEX .
2		No	Go to next step.
3	DETERMINE THE CONDITION Key in ON position. Enter the following diagnostic mode on the scan tool: Instrument Cluster DataLogger Select the instrument cluster parking brake (PRKSWAPPL) PID. Apply and release the parking brake while monitoring the instrument cluster parking brake switch PID. Does the PID agree with the parking brake position?	Yes	Go to step 6.
3		No	Go to next step.
4	CHECK THE PARKING BRAKE SWITCH Key in OFF position. Disconnect: Parking Brake Switch connector 0918-201. Key in ON position. Observe the parking brake indicator. Did the brake warning indicator turn off?	Yes	INSTALL a new parking brake switch. TEST the system for normal operation.
4		No	Go to next step.
5	CHECK CIRCUIT (GY/L) FOR A SHORT TO GROUND Key in OFF position. Disconnect: Instrument Cluster connector 0922-101. Measure the resistance between the parking brake switch 0918-201 pin 1, circuit (GY/L), harness side and ground. Is the resistance greater than 10,000 ohms?	Yes	Go to step 9.
5		No	REPAIR the circuit. TEST the system for normal operation.
6	CHECK THE ABS MODULE OPERATION Key in OFF position. Disconnect: ABS Module connector 0413-102. Connect a fused (5A) jumper wire between the ABS module 0413-102 pin 27, circuit (G/V), harness side and ground. Key in ON position. Does the brake warning indicator turn off after prove-out?	Yes	REMOVE the jumper wire. Go to step 8.
6		No	REMOVE the jumper wire. Go to next step.
7	CHECK CIRCUIT (G/V) FOR AN OPEN Key in OFF position. Disconnect: Instrument Cluster connector 0922-101. Measure the resistance between the ABS module 0413-102 pin 27, circuit (G/V), harness side and the instrument cluster 0922-101 pin 16, circuit (G/V), harness side. Is the resistance less than 5 ohms?	Yes	Go to step 9
7		No	REPAIR the circuit. TEST the system for normal operation.
8	CHECK FOR CORRECT ABS MODULE OPERATION Disconnect the ABS module connector. Check for: corrosion damaged pins pushed-out pins Connect the ABS module connector and make sure it seats correctly. Operate the system and verify the concern is still present. Is the concern still present?	Yes	INSTALL a new ABS module. See ANTI-LOCK BRAKE SYSTEM (ABS) MODULE . TEST the system for normal operation.
8		No	The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.
9	CHECK FOR CORRECT INSTRUMENT CLUSTER OPERATION Disconnect all the instrument cluster connectors. Check for. corrosion damaged pins pushed-out pins Connect all the instrument cluster connectors and make sure they seat correctly. Operate the system and verify the concern is still present. Is the concern still present?	Yes	INSTALL a new instrument cluster. See INSTRUMENT CLUSTER TEST the system for normal operation.
9		No	The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.