1. Verify the customer complaint.
2. Follow the radio service procedures.
3. If technical assistance is required, acquire all pertinent information before calling for technical assistance.

1. If the left speaker or the right speaker operates normally except with the remote cassette (optional) in the playback mode, repair the open in CKT 1406 (left) or CKT 1407 (right) between the cassette player and the radio.
2. If the radio clock memory is inoperative, inspect for an open in CKT 1740 between the right side IP wiring harness junction block and the radio. If CKT 1740 is OK, service the radio.
3. Repair the open in CKT 835 between the cassette player and the radio if the following conditions exist:

•	The remote cassette player (optional) is inoperative.

•	The cassette ejects only with the ignition switch in the OFF position.

4. Acquire any available technical service bulletins.
5. If the radio display does not dim with the headlamp switch in the PARK or the HEAD position, inspect CKT 9 for an open. If CKT 9 is OK, service the radio.
6. If the radio display is lit and the backlit switches are not lit, inspect CKT 8 for an open. If CKT 8 is OK, service the radio.
7. For reception concerns, determine if the station is obtainable in the customer's listening area.
8. In order to test for audio reception/noise, position the vehicle outside the building with the hood closed.
9. Duplicate the customer's complaint before attempting to diagnose the system.

9.1.	Ask the customer to demonstrate the condition.

9.2.	Test drive the vehicle with the customer.

9.3.	Test drive a similar model vehicle with a similar audio system.

9.4.	Compare the sound quality in the two vehicles in order to determine if the condition is abnormal.

10. Before diagnosing the system, identify the following items:

•	The components

•	The component features

•	The customer's complaint

11. If any aftermarket equipment was installed on the vehicle, perform the following procedure:

11.1.

Disconnect the aftermarket equipment.

11.2.

Determine if the customer's complaint still exists.

11.3.

Follow GM guidelines for installation of aftermarket components.

12. Perform the following steps in order to identify a noisy component:

12.1.

Identify the ignition key switch position in which the noise appears, including the following positions:

•	Key ON with the engine not running

•	Key ON with the engine running

12.2.

Remove the fuses one at a time until the complaint condition is eliminated.

12.3.

Mark the complaint fuse(s). Reinstall all of the fuses and the circuit breakers.

12.4.

Refer to Power Distribution Schematics in Wiring Systems in order to identify all the systems and components powered by the complaint fuse(s).

12.5.

Disconnect the components powered by the complaint fuse(s) one at a time until the complaint condition is eliminated and the noisy component is identified.

12.6.

Inspect the ground integrity of the complaint-causing component.

13. Consider the following points when diagnosing noise in the system:

•	An interference condition is NOT necessarily an audible noise.

•	Most noises are found on weak stations near the low end of the band. These noises are part of a normal condition.

•	An ignition noise on the FM band may indicate a possible defective ignition system.

•	The following items may induce noise or poor reception:

-	Malfunctioning and marginal components

-	Malfunctioning and marginal relays

-	Malfunctioning and marginal solenoids

14. Inspect for a broken (or partially broken) wire inside the insulation. A broken wire may cause a system malfunction but prove GOOD in a continuity/voltage inspection with the system disconnected. The circuits may be intermittent when loaded. Monitor the circuits for a voltage drop with the system operational (under load).

Important: Electromagnetic Interference (EMI) may cause a fewer number of stations to be received in one of the three modes. Various vehicle components may cause the EMI. This EMI may be the cause of the differences in reception. Inspect for components powered up in the three various key positions. This action may eliminate one or more of the following components:

Radio Inoperative:

1. Verify that G202 is clean and tight.
2. Visually inspect the following fuses:

•	The RADIO ACCESSORY fuse

•	The RADIO BATTERY fuse

3. In order to inspect a speaker, use a C or D cell battery in order to perform the following procedure:

3.1.	While momentarily connecting and disconnecting the battery across the circuits to the speaker, perform the following actions:

•	Listen for a slight popping sound.

•	Watch the cone of the speaker in order to ensure that the cone moves in and out.

3.2.	Verify that one of the above actions occurs. If either action occurs, the speaker and the circuitry are usually OK.

If the installation of this filter causes turn ON or turn OFF delays (or other noticeable performance concerns), remove the filter. Install a 0.47 mF capacitor to ground in place of the filter that was just removed.

Important: Before measuring the resistance of the antenna, perform the following steps:

1. Remove the negative lead of the battery.
2. Zero the meter.

1. Select stations within range.

The best FM fidelity is obtained from stations within a 16-64 km (10-40 mi) range. Beyond 64 km (40 mi), noise and flutter may appear due to the line of sight range limitations of FM signals.

SOLUTION: Reduce the treble response by moving the treble control down (or to the left) in fringe areas. On EQ Radios, slowly slide the 10K control down.

2. Realize that tall structures may interfere.

Tall buildings or hills may cause shadows or cancellation of FM signals. This effect is similar to the ghost effect or flutter effect noticed on the television sometimes when airplanes fly in the vicinity. The shadow or cancellation of the FM signal sounds like a pop or momentary hiss.

SOLUTION: Reduce the treble or the 10K setting to a lower volume.

3. Realize that other stations may cause interference.

Although the circuits in Delco® receivers are the most advanced available, rare instances occur where a station being listened to is interfered with by another station. This effect only occurs when the stations are almost on the same frequency and certain geographical criteria are present.

SOLUTION: Select another station or switch to a tape.

Reception Characteristics

AM does not have the flutter characteristics of FM (caused by tall buildings or hills). AM is subject to interference from the following items:

Ways To Reduce Noise

1. Move the treble control down.
2. Tune to a stronger station.