Audio System Diagnostic Overview
Important: Electromagnetic Interference (EMI) can cause a fewer number of stations
to be received in one of the three modes. The EMI can be caused by various
vehicle components. This may be the cause of the differences in reception.
Check for components powered up in the three various key positions. This
may eliminate engine running components, ignition on components, etc. For
example, if the same number of stations are received with the engine running
as when the engine was off, the components active with the engine running
are not causing the interference. Perform the following:
| • | Determine type of audio complaint. |
| • | Try to duplicate condition (listen to AM or FM, start vehicle,
put in a good CD or cassette, test switches, etc.) |
- Verify customer complaint.
- Follow radio service procedures.
- If technical assistance is required, have all the pertinent information
available before placing the call.
Identifying Concerns
| • | Check for technical service bulletins. Check the Dealer Communication
System for any applicable Preliminary Information (P/I) for customer concerns. |
| • | For reception concerns, determine if the station is obtainable
in the customer's listening area. |
| • | To test for audio reception/noise, position the vehicle outside
of the building with the engine compartment lid down. |
| • | Duplicate the customer's complaint before trying to diagnose the
system. Have the customer demonstrate the condition. Test drive the vehicle
with the customer and then test drive another similar model vehicle (with
a similar audio system) to do a comparison of the two vehicles to determine
if the condition is abnormal. |
| • | Before diagnosing, identify components, their features and the
customer's complaint. |
| • | Determine if any aftermarket equipment is installed on the vehicle.
Disconnect the aftermarket equipment and determine if the customer's complaint
still exists. Follow GM guidelines for installation of aftermarket components. |
| • | Perform the following steps to identify a noisy component: |
| 1. | Identify ignition switch position in which the noise appears,
such as: accessory, on (engine not running), and on (engine running). |
| 2. | Remove fuses one at a time until the complaint condition has been
eliminated. |
| 3. | Mark the complaint fuse(s) and reinstall all fuses and circuit
breakers. |
| 5. | Disconnect the components powered by the complaint fuse(s) one
at a time until the complaint condition has been eliminated and the noisy
component is identified. |
| 6. | Check the ground integrity of the complaint causing component. |
| • | An interference condition is not necessarily an audible noise. |
| • | Most noises can be found on weak stations near the low end of
the band and are considered to be a normal condition. |
| • | Ignition noise on FM could indicate a possible defective ignition
system. Malfunctioning and marginal components, relays, and solenoids may
induce noise and/or poor reception. |
Error Codes
Display
| Error Condition
|
E10
| Tight Tape
|
E11
| Broken Tape
|
E14
| Wrapped Tape
|
E20
| CD Optics Focus Error
|
E21
| CD Optics Loss of Tracking Control
|
E30
| CD Changer Optics Focus Error
|
E31
| CD Changer Optics Loss
of Tracking Control
|
E34
| CD Changer Door Open
|
Corrective Action
| • | Use proper tools for diagnostics and repairs. |
| • | Follow Electrostatic Discharge (ESD) guidelines. Refer to Handling ESD Sensitive Parts Notice
in General Information. |
| • | Use available noise suppression devices: |
| - | 220 mF (50V) 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 |
| - | 21 inch braided ground strap GM P/N 8910791 |
| - | 19 inch braided ground strap GM P/N 6286800 |
| - | 10.5 inch braided ground strap GM P/N 6287160 |
| - | 8.5 inch braided ground strap GM P/N 12091511 |
| • | Utilize the Test Tape/CD Diagnostic Kit GM P/N J 39916-A
to optimize proper audio diagnostics. Refer to
Speakers General Diagnosis
in Entertainment for more information. |
| • | If the condition requires the radio to be sent to the service
center, describe the symptoms on the warranty form accurately. Along with
the warranty form, send a copy of the Service Writer Check List with the
unit. |
| • | Do not leave a CD disc or tape in the car. Extreme heat could
cause permanent damage. Cassette tapes could be damaged if not stored in the
case. The vibration in the vehicle can cause the tape to unwind inside
the cartridge. |
| • | Before removing speaker(s), check all connectors and wiring to
the speaker(s). Examine the connectors for bent or loose pins. |
| • | If a test antenna is used in diagnostics, ground the antenna base
to the vehicle body and do not hold the mast. |
| • | Check the antenna coax connectors for corrosion or bad connections/crimps.
Route coax separately from the other wires. Shield antenna coax interconnections
with aluminum or nickel tape. |
| • | Check all vehicle grounds, NOT just radio and antenna grounds. |
| • | Coated screws or bolts can act as poor grounds. |
| • | Always use a braided ground strap when applying grounds. Keep
the ground strap as short as possible, the shorter the ground strap the better. |
| • | When shielding the instrument panel, wires, hoses (most hoses
are conductive unless they have a white stripe), etc., use aluminum foil tape
or nickel tape to shield against magnetically induced interference. For
optimum results, try varying the following ground techniques: |
| - | 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. |
| • | When shielding a harness with tape, attach a ground strap to the
end of the tape and then wrap the strap 360° around the tape securing
the other end of the strap to a known good chassis ground. |
| • | Any interference is best corrected by suppression at the source
of the interference, if possible. |
| • | Care should be used when applying suppression. Signal wires (such
as sensor outputs, clock, and communication circuits) cannot be suppressed.
Battery and ignition wires can be suppressed. After adding any suppression,
all vehicle systems (even those not related to the audio system) should
be checked for proper operation and function. |
| • | Interference can usually be eliminated by shielding/grounding
or suppressing. |
| • | Capacitors work best on switch pops and low frequency noise. Filters
work best on high frequency whines and static. |
| • | Whenever possible, make a test harness that includes filters and
capacitors. Always check the effectiveness and operation before permanently
installing a fix. |
| • | Recommended capacitor application for an audible pop induced from
a switching operation is: |
| - | 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 engine running,
perform the following checks: |
| - | Check the integrity of the ignition system (proper spark plug
wire routing, no misfiring, etc.). |
| - | Check the integrity of the engine compartment grounds. |
| - | Check for malfunctioning relays, solenoids, or other components
which may be inducing noise or poor reception. |
| - | Check the ground integrity of the complaint causing component. |
Generator Whine Concerns
| • | Check the ground terminal on the battery. |
| • | Check for coated mounting bolts on the generator bracket. |
| • | Check for a faulty mounting of the generator to the engine. |
| • | Make sure all ground straps between the engine and the frame are
clean and tight. |
| • | Try the following fixes: |
| - | If noise is still present, check the charging system Refer to
Charging System Check
in Engine Electrical. |
| - | If the charging system is functioning normally, check for technical
service bulletins on generator whine. |
| - | Install a filter GM P/N 1224205 in the battery feed to the radio. |
| - | Try installing the filter with the following variations if noise
is not eliminated. |
| 1. | Remove the ground to the filter. |
| 2. | Reverse the filter so the two wire side is toward the radio with
the ground wire attached to a good ground. |
| 3. | Remove the ground from the filter. |
| - | If noise is still present, install another filter GM P/N 1224205
in the ignition feed to the radio. Install using the same variations as the
first filter. If the installation of this filter causes turn on or turn
off delays or other noticeable performance concerns, remove it and install
a 0.47 mF capacitor to ground in its place. |
| - | Remove any unneeded filters after repair, before reassembling
the vehicle. |
How to Enjoy FM Stereo
- Select Stations Within Range - The best FM fidelity will be obtained
from stations within a 16-64 km (10-40 mile) range. Beyond that noise
or flutter may begin to appear due to the line of sight range limitations
of FM signals. Solution: Reduce treble response by reducing the treble
control in fringe areas.
- Realize Tall Structures Can Interfere - Tall buildings or hills
may cause shadows or cancellation of FM signals (this is similar to the ghost
or flutter effect seen on television sometimes when airplanes are flying
in the vicinity). It will sound like a pop or momentary hiss. Solution:
Reduce the treble control.
- Interference from Another Station - Although the circuits in Delco
receivers are the most advanced available, there are rare instances where
a station being listened to will be interfered with by another station.
This only happens when the stations are on almost the same frequency and
certain geographical criteria are present. Solution: Select another station
or switch to tape.
How To Enjoy AM
Reception Characteristics: AM does not have the flutter characteristics
of FM (caused by tall buildings, hills, etc.). However, it is subject to interference
from power lines, neon signs, atmospheric conditions, and unwanted stations.
Ways to reduce noise:
| • | Tune to a stronger station. |
