Audio System Diagnostic Overview
Important: Electromagnetic Interference (EMI) can cause reception of fewer stations.
Various components within the vehicle can be the cause of EMI. Inspect the
components which are powered up in various key positions in order to eliminate
possible causes of the interference.
- Verify customer concern.
| • | Determine the type of audio concern. |
| • | Try to duplicate the condition. |
| - | Put in a good CD or cassette. |
- Follow radio service procedures.
- If technical assistance is required, have all the pertinent information
available before placing the call.
Identifying Concerns
| • | Examine the technical service bulletins. Examine 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. |
| • | Test for audio reception/noise by positioning the vehicle outside
of the building with the engine compartment lid down. |
| • | Duplicate the customer's concern before trying to diagnose the
system. Ask the customer to demonstrate the condition. Test drive the vehicle
with the customer, and then test drive another similar model vehicle (with
a similar audio system). Compare the two vehicles in order to determine
if the condition is abnormal. |
| • | Before diagnosing, identify the components, their features, and
the customer's concern. |
| • | Determine if any aftermarket equipment is installed on the vehicle.
Disconnect the aftermarket equipment and determine if the customer's concern
still exists. Follow GM guidelines for installation of aftermarket components. |
| • | Perform the following steps in order to identify a noisy component: |
| 1. | Identify the ignition switch position in which the noise appears: |
| • | ON (engine not running) |
| 2. | Remove fuses one at a time until the noise condition has been
eliminated. |
| 3. | Mark the suspected fuse. |
| 4. | Reinstall all fuses and circuit breakers. |
| 6. | Disconnect the components powered by the suspected fuse, one at
a time until the noise condition has been eliminated and the noisy component
is identified. |
| 7. | Inspect the ground integrity of the component causing the condition. |
| • | An interference condition is not necessarily an audible noise. |
| • | Most noises can be found on weak stations near the low end of
the band. This is considered to be normal. |
| • | 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 the Electrostatic Discharge (ESD) guidelines. Refer to Handling ESD Sensitive Parts Notice
in General Information. |
| • | Use available noise suppression devices: |
| - | 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 |
| - | 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 |
| • | If you must return the radio to the service center, accurately
describe the symptoms on the warranty form. Send a copy of the service writer
check list with the unit. |
| • | Do not leave a CD disc or a 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 a speaker, inspect all of the connectors and wiring
to that speaker. Examine the connectors for bent or loose pins. |
| • | If you use a test antenna in diagnostics, ground the antenna base
to the vehicle body and do NOT hold the mast. |
| • | Inspect the antenna coax connectors for corrosion or bad connections/crimps.
Route the coax separately from the other wires. Shield the antenna coax interconnections
with aluminum or nickel tape. |
| • | Inspect all vehicle grounds, NOT just the radio and the antenna
grounds. |
| • | Coated screws or bolts are poor grounds. |
| • | Always use a braided ground strap when applying grounds. Keep
the ground strap as short as possible. |
| • | Use aluminum foil tape or nickel tape when shielding the instrument
panel, wires, hoses, etc., in order 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. Then wrap the strap 360 degrees around the tape securing
the other end of the strap to a known good chassis ground. |
| • | Correct the interference by suppression at the source of the interference,
if possible. |
| • | Use caution when applying suppression. You cannot suppress signal
wires (such as sensor outputs, clock, and communication circuits). You can
suppress battery and ignition wires. After adding 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. |
| • | Whenever possible, make a test harness that includes filters and
capacitors. Always test the effectiveness and operation before permanently
installing a fix. |
| • | For an audible pop induced from a switching operation, use the
following capacitor application: |
| - | 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 an audio concern is only present with the engine running, perform
the following inspections: |
| - | Inspect the integrity of the ignition system (proper spark plug
wire routing, no misfiring, etc.). |
| - | Inspect the integrity of the engine compartment grounds. |
| - | Inspect for malfunctioning relays, solenoids, or other components
which may be inducing noise or poor reception. |
| - | Inspect the ground integrity of the component which is causing
the concern. |
Generator Whine Concerns
| • | 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. |
| • | Clean and tighten all ground straps between the engine and the
frame. |
| • | Try the following fixes: |
| - | If the charging system is functioning normally, examine the 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 the filter 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 that 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 when airplanes are flying
in the vicinity). The interference 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, sometimes another
station will interfere with a station being listened to. This only happens
when the stations are on almost the same frequency and when certain geographical
criteria are present. Solution: Select another station or switch to tape. |
How To Enjoy AM
AM does not have the flutter characteristics of FM (caused by tall buildings,
hills, etc.). However, AM radio is subject to interference from power lines,
neon signs, atmospheric conditions, and unwanted stations.
Ways to reduce noise:
| • | Tune to a stronger station. |
