Audio System Diagnostic Overview
- Verify the customer complaint.
- Follow the radio service procedures.
- If you call for technical assistance, assemble all of the pertinent
information before you place the phone call.
Identifying Concerns
Refer to any technical service bulletins. Also refer to the Dealer Communication
System. The Dealer Communication System will provide any applicable Preliminary
Information (P/I) for customer concerns.
Determine if any DTCs are stored. Refer to Engine Controls.
If the reception is poor, determine if the station is within the customer's
listening area.
Before you test for audio reception or noise, position the vehicle outside
of the building with the hood closed.
Duplicate the customer's complaint before you begin to diagnose the
system:
- Ask the customer to demonstrate the
condition.
- Compare the vehicle to another vehicle
in order to determine if the condition is abnormal:
| • | Test drive the vehicle with the
customer. |
| • | Test drive another vehicle that is a similar
model with a similar audio system. |
Before you begin diagnosis, identify which components are involved and
the features of these components.
Determine if any aftermarket equipment has been installed on the vehicle.
Complete the following steps if aftermarket equipment is present:
- Disconnect the aftermarket equipment.
- Determine if the customer's complaint still exists.
- Reinstall the equipment as needed. Refer to GM guidelines
for the installation of the aftermarket components.
Complete the following steps in order to identify a faulty component:
- Place the ignition into the following
positions. Determine in which position the noise is audible:
| • | The ON position, with the engine off |
| • | The ON position, with the engine running |
- Remove the fuses one at a time until the condition is gone.
- Mark the fuse or fuses that cause the condition.
- Reinstall all of the fuses and the circuit breakers.
- Determine which systems and components are powered by the
faulty fuse or fuses. Refer to
Power Distribution Schematics
in Wiring Systems.
- Disconnect
each of the components that is powered by the complaint fuse or fuses.
Disconnect the components one at a time.
- When
the condition is gone, identify the noisy component.
- Inspect the ground integrity of the component that is causing the condition.
An interference condition may not be an audible noise.
Most noises can be heard on weak stations near the end of the band.
These noises are normal.
An ignition noise on FM may indicate that the ignition system is flawed.
Malfunction in the following items may cause noise or poor reception:
Error Codes
Display
| Error Condition
|
E10
| Tight Tape
|
E11
| Broken Tape
|
E14
| Wrapped Tape
|
Corrective Action
Use the correct tools for diagnosis and repairs. Be sure to follow the
ESD guidelines.
The following noise suppression devices are available:
| • | 220 mF (50 V) capacitor
GM P/N 1227895 |
| • | 0.47 mF capacitor
GM P/N 1227894 |
| • | Fuse block capacitor
GM P/N 469328 |
| • | Feed through capacitor
GM P/N 477371 |
| • | Filter package GM P/N 1224205 |
| • | Turn signal suppression GM P/N 3861565 |
| • | Fuel pump suppressor GM P/N 25027405 |
| • | 53.3 cm (21 in) braided ground strap
GM P/N 8910791 |
| • | 48.3 cm (19 in)
braided ground strap GM P/N 6286800 |
| • | 26.7 cm (10.5 in) braided ground strap GM P/N 6287160 |
| • | 21.6 cm (8.5 in) braided ground strap
GM P/N 12091511 |
Use the Test Tape/CD Diagnosis Kit GM P/N J 39916-A
to assist in optimizing diagnosis.
If the condition requires you to send the radio to the service center,
describe the symptoms accurately on the warranty form. Send a copy of the
Service Writer Check List along with the warranty form.
Take the following precautions in order to prevent damage to cassettes:
| • | Do not leave cassettes in the car.
Extreme heat may cause permanent damage to cassettes. |
| • | Store cassettes in their cases. The vibration in the vehicle may cause
the tape to unwind inside of the cartridge. |
Complete the following steps before you remove the speakers:
| • | Inspect all of the connectors and
wiring to the speakers. |
| • | Examine the connectors for
bent or loose pins. |
Complete the following steps if you use a test antenna in diagnosis:
- Ground the antenna base to the vehicle
body. Do not hold the mast.
- Inspect the antenna coax
connectors for the following conditions:
- Shield the antenna coax interconnections with aluminum or nickel
tape.
- Inspect the following grounds:
| • | All of the remaining
grounds in the vehicle |
Coated bolts and screws may be poor grounds.
Use a braided ground strap when you apply a ground. Keep the ground
strap as short as possible.
Radio
Use aluminum foil tape or nickel tape in order to shield against magnetically
induced interference when shielding the following components:
| | Most hoses are conductive unless the hoses have a white stripe. |
Vary the following ground techniques for optimum grounding results:
| • | Add a ground at both ends of the
tape. |
| • | Add a ground to just one end of the tape. |
| • | Do not add ground to the tape. |
Complete the following steps when shielding a harness with tape:
| • | Attach a ground strap to the end
of the tape. |
| • | Wrap the strap 360 degrees around
the tape. |
| • | Secure the other end of the strap to a
known good chassis ground. |
If possible, correct any interference at the source of the interference.
Apply suppression carefully. The following wires can be suppressed:
Signal wires cannot be suppressed. The following wires are examples
of signal wires that cannot be suppressed:
| • | The communication circuits |
After you apply suppression, inspect all of the vehicle systems for
correct operation.
Interference is usually eliminated with the following procedures:
Use capacitors in order to correct the following conditions:
Use filters in order to correct the following conditions:
Whenever possible, make a test harness that includes filters and capacitors.
Always verify that a repair is effective and that the systems operate correctly
before you permanently install a fix.
Use one of the following capacitor applications for an audible pop that
is induced by a switching operation:
| • | Add a capacitor across the contacts
of the switch. |
| • | Add a capacitor from the hot side
of the switch to the ground. |
| • | Add a capacitor to each
side of the switch to the ground. |
Complete the following inspections if the condition is present only
when the ignition is in the RUN position and the engine is running:
| • | Inspect the integrity of the ignition
system. Refer to Engine Controls. |
| • | Inspect the integrity
of the engine compartment grounds. |
| • | Inspect for the
following conditions that may cause noise or poor reception: |
| - | Malfunctioning solenoids |
| - | Malfunctioning
system components |
| • | Inspect the integrity of the ground for the component that is
causing the complaint. |
Perform the Antenna System test for noise or poor reception. Repair
the system as needed. Refer to
Radio Poor Reception
for diagnosis.
Generator Whine Concerns
Complete the following inspections:
| • | Inspect the ground terminal on
the battery. |
| • | Inspect for coated mounting bolts on
the generator bracket. |
| • | Inspect for a faulty mounting
of the generator to the engine. |
| • | Verify that all of
the ground straps between the engine and the frame are clean and tight. |
Complete the following repairs as needed:
- If the noise is still present, inspect
the charging system. Refer to
Diagnostic System Check - Engine Electrical
in Engine Electrical.
- If the charging system is functioning normally, refer to any technical
service bulletins on generator whine.
- Install a filter
GM P/N 1224205 in the battery feed to the radio.
- If the noise is still present, install the filter with the following
variations:
| • | Install the filter with the single
wire side toward the radio. |
| • | Attach the ground wire to a good ground. |
| • | Remove the ground to the filter. |
| • | Reverse the
filter so that the two wire side is toward the radio and the ground wire is
attached to a good ground. |
| • | Remove the ground from the filter. |
- If the noise is still present, install another filter GM P/N 1224205
in the ignition feed to the radio.
Install the filter using the same variations as in the first filter.
If the installation of this filter causes turn on or turn off delays
or other performance concerns, complete the following steps:
| 5.2. | Install a 0.47 mF capacitor to ground in the filter's place. |
- Remove any unneeded filters after the repair, before you reassemble
the vehicle.
Radio Noise
Use a noise sniffer in order to aid in diagnosing the radio noise.
Inspect the radio reception in an area that is free of the following
items:
Ignition noise on FM may indicate that the electronic ignition (EI)
system is defective.
Inspect the antenna coax connectors for the following conditions:
If you use a test antenna, ground the base of the test antenna to the
vehicle body.
Coated screws or bolts can act as a poor ground.
Notice To Technicians
Electromagnetic interference (EMI) can cause a fewer number of stations
to be received in one of the three modes. Various vehicle components may cause
EMI. EMI may cause of the differences in reception.
Inspect for components that are powered up in the three various key
positions. This action will eliminate some sets of conditions. For example,
if the same number of stations are received with the engine running
as when the engine was off, active components with the engine running
are not causing interference.
- Determine the type of audio complaint.
- Attempt to duplicate the condition:
| • | Play a known good
cassette. |
