Flow of Diagnosis

GENERAL INFORMATION
An RWAL system malfunction will be indicated by illumination of the ABS warning lamp. In most cases, the brake warning lamp will also be illuminated at the same time. If either or both warning lamps illuminate, the following six step troubleshooting procedure should be implemented.
^ Verify the customer's concern
^ Determine any related symptoms
^ Diagnose the concern
^ Isolate the concern
^ Repair the concern
^ Verify the repair

The RWAL diagnosis begins by verifying the customer's concern. This test starts by verifying the ABS warning lamp and brake warning lamp operation. When this test is complete, you will be instructed to perform either RWAL DIAGNOSTIC PROCEDURES TEST 1 or RWAL DIAGNOSTIC PROCEDURES TEST 2. The test usually will begin with a brief explanation of the procedure or provide guidelines for the test. Then, you will begin with step 1. Each test has four columns; STEP, ACTION, YES and NO. You will be guided through each test by the ACTION. The ACTION questions will all have bullets (^) in front of them. Answer all questions either with a YES or NO statement. The YES or NO columns will guide you to the next appropriate test.

VERIFYING THE CUSTOMER'S CONCERN
Start the engine and monitor the brake warning lamp and ABS warning lamp. Both lamps will illuminate for a few seconds when the ignition is turned on. If the brake warning lamp and or ABS warning lamp remain illuminated or do not come on, continue on to the RWAL DIAGNOSTIC TEST PROCEDURES TEST 1. If the warning lamps illuminate for a few seconds and then go out, proceed with this test. With the engine running and the vehicle in PARK or NEUTRAL, check the service brake. The brake pedal should remain firm under steady foot pressure and not travel too far towards the floor. The vehicle can be test driven if is determined that the base brake system is functioning normally. Refer to the Brakes if the previous checks determine a malfunction with the base brakes.

TEST DRIVING VEHICLE
Most RWAL complaints will require a test drive as part of the diagnostic procedure. The purpose of the test drive is to duplicate and verify the customer's concern.

WARNING: REDUCED BRAKING MAY BE ENCOUNTERED IF THE VEHICLE IS TEST DRIVEN WITH EITHER THE BRAKE WARNING LAMP OR THE ABS WARNING LAMP ILLUMINATED. EXTREME CAUTION SHOULD BE USED.

Perform both normal and firm braking stops in the 25 - 40 mph range. At least one complete ABS stop should be performed. Determine if there are any unusual brake operating conditions such as vehicle lead during braking, brakes grabbing, brakes dragging, noise, low brake pedal, etc. If the brake warning lamp and or ABS warning lamps illuminate during the test drive, proceed to the RWAL DIAGNOSTICS PROCEDURES TEST 1. If the vehicle leads during braking, the brakes grab, the brakes are dragging, there is brake related noise, a low brake pedal, etc., refer to Brakes. If the warning lamps remain extinguished and the brakes respond normally, then proceed to the RWAL DIAGNOSTIC PROCEDURES TEST 2.

NOTE: If either warning lamp is illuminated, a DTC should have been generated. Certain Diagnostic Trouble Codes (DTCs) are erased when the ignition key is turned to OFF. Do not turn the ignition key OFF until you have recorded the DTC. Refer to SELF DIAGNOSIS for instructions on retrieving any DTC.