Initial Inspection and Diagnostic Overview: Service Precautions

^ Inspect the antenna coax connectors for corrosion or bad connections/crimps. Route coax separately from the other wires. Shield the antenna coax interconnections with aluminum or nickel tape.
^ Verify all vehicle grounds, not just the radio and antenna grounds. Refer to the Antenna Diagnostic.
^ If you use a test antenna in diagnostics, ground the antenna base to the vehicle body. Do not hold the mast.
^ Coated screws or bolts may act as poor grounds.
^ Always use a braided ground strap when you apply grounds. Keep the ground strap as short as possible. The shorter the ground strap, the better.
^ When you shield the dash, wires, hoses (most hoses are conductive unless the hose has a white stripe), etc., use only aluminum foil or nickel tape in order to protect against magnetically induced interference. For optimum results, vary the following ground techniques:
- Add a ground at both ends of the tape.
- Add a ground to just 1 end of the tape.
- Do not add ground to the tape.
^ When you shield a harness with tape, attach a ground strap to the end of the tape and wrap the strap 360° around the tape, then secure the other end of the strap to a known good chassis ground.
^ Correct any interference by means of supersession at the source of interference, if possible.
^ Care should be used when you apply suppression. Do not suppress signal wires such as the sensor outputs, the clock, and the communication circuits. You can suppress battery and ignition wires. After you add any suppression, inspect all vehicle systems (even those not related to the audio system) for proper operation and function.
^ You can usually eliminate interference by shielding/grounding or suppressing.
^ Capacitors work best on switch pops and low frequency noise. Filters work best on high frequency whines and static.
^ Make a test harness that includes filters and capacitors whenever possible. Always inspect the effectiveness and operation before you permanently install a FIX.
^ The recommended capacitor application for an audible pop induced from a switching operation is to:
- Add a capacitor across the contacts of the switch.
- Add a capacitor from the hot side of the switch to ground.
- Add a capacitor to each side of the switch to ground.
^ If a complaint condition is only present with the ignition key in the RUN position with the engine running, perform the following inspections:
- Inspect the integrity of the ignition system (proper spark plug wire routing, no misfiring, etc.). Refer to Starting and Charging. Starting and Charging
- Inspect the integrity of the engine compartment grounds.
- Inspect for malfunctioning relays, solenoids, or other components which may include noise or poor reception
- Inspect the ground integrity of the complaint causing component.