Diagnosis and Testing - Front

FRONT

WARNING: To avoid serious or fatal injury on vehicles equipped with airbags, disable the supplemental restraint system before attempting any steering wheel, steering column, airbag, seat belt tensioner, impact sensor, or instrument panel component diagnosis or service. Disconnect and isolate the battery negative (ground) cable, then wait two minutes for the system capacitor to discharge before performing further diagnosis or service. This is the only sure way to disable the supplemental restraint system. Failure to take the proper precautions could result in accidental airbag deployment.

If the front wiper motor operates, but the wipers do not move on the windshield, replace the ineffective front wiper linkage module. If the front washer pump/motor operates, but no washer fluid is dispensed on the glass; or, if the wipers operate, but chatter, lift, or do not clear the glass, clean and inspect the front wiper and washer system components as required. Wipers/Washers - Cleaning and Wipers/Washers - Inspection.

The hard wired front wiper and washer system circuits and components may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, details of wire harness routing and retention, connector pin-out information and location views for the various wire harness connectors, splices and grounds.

However, conventional diagnostic methods will not prove conclusive in the diagnosis of the front wiper and washer system or the electronic controls or communication between other modules and devices that provide some features of the front wiper and washer system. The most reliable, efficient, and accurate means to diagnose the front wiper and washer system or the electronic controls and communication related to front wiper and washer system operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.

FALSE WIPES (AUTOMATIC WIPER ONLY)

False wipes are unnecessary wipes that occur when the control knob of the multi-function switch is in the I (Automatic) wiper position and no rain or moisture is apparent within the wipe pattern on the windshield glass. Because this system is designed to operate whenever it detects moisture, if the switch is in the automatic wiper position any road spray, bug splatters, or mist from passing cars or trucks may occasionally cause the wipers to cycle. These are normal characteristics of this system and are not false wipes.

False wipes generally are the result of foreign material or flaws that interfere with the system optics. The optics for this system allow the rain/light sensor to precisely transmit several InfraRed (IR) light beams and precisely monitor the intensity of these beams on the outer surface of the windshield glass to determine the presence of moisture. The sensitivity of this system is such that anything that distorts the focus or intensity of the IR light beams or affects the ability of the photo diodes within the sensor to see and accurately measure these light beams can result in the sensor misinterpreting the resulting input data as moisture on the windshield. The optics for this system include the lenses of the sensor, the adhesive layer that bonds the sensor bracket to the inside of the windshield, and the windshield glass itself.

The following procedure should only be used if false wipe occurrences are frequent and persistent. Perform diagnosis of the front wiper system, the multi-function switch, the Steering Control Module (SCM), the Body Control Module (BCM) and the rain/light sensor using a diagnostic scan tool and the appropriate diagnostic procedures before performing the following:

1. Carefully inspect the outer surface of the windshield glass for physical damage, including scratches, cracks or chips in the vicinity of the rain/light sensor mounting bracket. Scratches, cracks or chips in the windshield glass outside the area of the RSM mounting bracket will not cause false wipes. If OK, go to STEP 2. If not OK, replace the damaged windshield.
2. From the outside of the windshield glass, carefully inspect the adhesive layer between the windshield glass and the rain/light sensor bracket for any large voids. If an adhesive void greater than about 1 millimeter (0.04 inch) is observed, remove and reinstall the sensor mounting bracket. If OK, go to STEP 3.
3. Remove the rain/light sensor trim cover from below the inside rear view mirror and lightly pull the sensor away from the mounting bracket on the windshield to confirm that the sensor is fully engaged with the bracket on the inside of the windshield glass. If OK, go to STEP 4. If not OK, remove and reinstall the sensor onto the bracket as required.
4. Remove the sensor from the mounting bracket. Inspect the sensor lens and the mounting bracket for contamination. If OK, go to STEP 5. If not OK, clean any foreign material from the lens using rubbing alcohol and a lint-free cloth.
5. Carefully inspect the sensor for any physical damage, including scratches on the sensor lens. If OK, go to STEP 6. If not OK, replace the damaged sensor.
6. Carefully inspect the sensor mounting bracket for any physical damage. If not OK, replace the damaged bracket.