C 1500 Truck 2WD V8-5.3L VIN T (1999)
Once proper diagnosis has been performed and documented, a thorough repair procedure is performed to fix the complaint. To confirm that the
repair has addressed the complaint, perform the appropriate system check. If the complaint is still present, re-examine the complaint, review the
first four steps of your strategy based diagnostics carefully.
IMPORTANT: Also verify the complaint under the conditions described by the customer before releasing the vehicle. The verification of the
repair in the form of a working test is the only way the repair process can be considered complete, this test should either be a road test or
performance test in the service bay.
Symptom Diagnostic Example
The following is an example of a symptom and the correct course of action taken by the technician.
IMPORTANT: Research for possible bulletins, DTCs and the vehicle's service history. Also, thoroughly screen the customer regarding the problem in
order to complete the repair of the vehicle and completely satisfy the customer when a DTC or a symptom diagnosis is not available.
Verify the Customer Concern, Check the Problem
Customer complaint is the head lamps are inoperative. Verify the normal operating procedure of the circuit and the components that share that
circuit. Refer to Strategy Based Diagnosis in Powertrain Management Testing. See: Computers and Control Systems
Review the Head lamps Electrical Schematic (Preliminary Checks)
Review the schematic, it is essential to understand how a circuit should work before trying to figure out why it doesn't. After understanding how a
circuit should operate, read the schematic again, this time keeping in mind what has been learned by operating the circuit. Since both the low beam
headlamps are inoperative, ensure that the following components are operating properly.
-
The headlamp Switch.
-
The YEL wire.
-
Low contacts of the Headlamp Dimmer Switch.
-
C100 terminal 1E.
-
The TAN wires.
-
Grounds G105 and G106.
Perform the System Check
The system check indicates that the low beam headlamps operate when the high beam switch is in high. Also, the high beam indicator illuminates
but neither high beam headlamp operates. Refer to Strategy Based Diagnosis.
Check for Bulletins
Utilizing a combination of Techline tools and the information accumulated from the Preliminary Checks, check for bulletins.
Isolate the Root Cause
At this point analyze and (diagnose the problem), and develop text. Since the high beam indicator illuminated when the headlamp dimmer switch
was in the high position, the high contacts of the headlamp dimmer switch and the LT GRN wire between the headlamp dimmer switch and C100
are good.
At this point, it is extremely unlikely that the high beam filaments in the RH and LH headlamp are both open or that both headlamp connections
are bad. The cause must be a bad connection at C100 or an open in the LT GRN wire between C100 and the RH headlamp.
