For 1990-2009 cars

Table 1: | Antenna System Resistance Values
Table 2: | Lead-in Cable Resistance Values

### Identifying Concerns

• | 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.

• | 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.

• | 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.

• | Acquire any available technical service bulletins. Inquire the dealer communication system for any applicable Preliminary Information (P/I) for customer concerns.

• | 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.

• | 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.

• | For reception concerns, determine if the station is obtainable in the customer's listening area.

• | In order to test for audio reception/noise, position the vehicle outside the building with the hood closed.

• | Duplicate the customer's complaint before attempting to diagnose the system.

1. | Ask the customer to demonstrate the condition.

2. | Test drive the vehicle with the customer.

3. | Test drive a similar model vehicle with a similar audio system.

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

• | Before diagnosing the system, identify the following items:

• | The components

• | The component features

• | The customer's complaint

• | If any aftermarket equipment was installed on the vehicle, perform the following procedure:

1. | Disconnect the aftermarket equipment.

2. | Determine if the customer's complaint still exists.

3. | Follow GM guidelines for installation of aftermarket components.

• | Perform the following steps in order to identify a noisy component:

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

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

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

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

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.

6. | Inspect the ground integrity of the complaint-causing component.

• | 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

• | 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).

### Corrective Action

• | Use the proper tools for diagnostic and repairs.

• | Follow ESD guidelines. Refer to Notice: Electrostatic discharge (ESD) can damage many solid-state electrical components. ESD susceptible components may or may not be labeled with the ESD symbol. Handle all electrical components carefully. Use the following precautions in order to avoid ESD damage:

• | Touch a metal ground point in order to remove your body's static charge before servicing any electronic component; especially after sliding across the vehicle seat.

• | Do not touch exposed terminals. Terminals may connect to circuits susceptible the ESD damage.

• | Do not allow tools to contact exposed terminals when servicing connectors.

• | Do not remove components from their protective packaging until required to do so.

• | Avoid the following actions unless required by the diagnostic procedure:

- | Jumpering or grounding of the components or connectors.

- | Connecting test equipment probes to components or connectors. Connect the ground lead first when using test probes.

• | Ground the protective packaging of any component before opening. Do not rest solid-state components on metal workbenches, or on top of TVs, radios, or other electrical devices.

.

• | Use the available noise suppression devices listed in the table below:

Application | GM Part Number
--- | ---
220 mF (50 V) capacitor | 1227895
0.47 mF capacitor | 1227894
Fuse block capacitor | 469328
Feed through capacitor | 477371
Filter package | 1224205
Turn signal suppression | 3861565
Fuel pump suppressor | 25027405
53.3 cm (21 in) braided ground strap | 12016624
48.3 cm (19 in) braided ground strap | 6286800
26.7 cm (10.5 in) braided ground strap | 6287160
21.6 cm (8.5 in) braided ground strap | 12091511

#### 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.

### Audio System Diagnostic Overview

• | Use the J 39916-A in order to optimize proper audio diagnostics.

• | If the condition requires the radio to be sent to the service center, accurately describe the symptoms on the warranty form. Send a copy of the Service Writer Check List with the unit and the warranty form.

• | Do not leave a CD or tape in the car. Extreme heat may cause permanent damage.

• | Do not store cassette tapes outside of the case. Vehicle vibration may cause the tape to unwind inside the cartridge.

• | Before removing the speaker(s), inspect all the connectors and the wiring to the speaker(s). Inspect the connectors for bent or loose pins. Refer to System Diagnosis in Wiring System.

| Important:

• | Inspect the antenna coax connectors for the following conditions:

- | Corrosion

- | Bad connections

- | Crimps

• | Route the coax separately from the other wires.

• | Shield the antenna coax interconnections using aluminum or nickel tape as described in the DE SSG.

• | Inspect all of the vehicle grounds, NOT just the radio and the antenna grounds. Refer to the Antenna Diagnostic Section.

• | If a test antenna is used 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 applying grounds. Ensure that the ground strap is as short as possible.

• | When shielding the following items, use aluminum foil tape or nickel tape in order to shield against magnetically-induced interference:

- | The dash

- | Wires

- | Hoses (most hoses are conductive unless the hose has a white stripe)

- | Other components

• | When shielding components, vary the following ground techniques in order to achieve optimum 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.

• | When shielding a harness using tape, perform the following steps:

1. | Attach a ground strap to the end of the tape.

2. | Wrap the strap 360 degrees around the tape securing the other end of the strap to a known chassis ground.

• | Correct any interference by using suppression at the source of the interference, if possible.

• | Use care when applying suppression. Do not suppress the following signal wires:

- | Sensor outputs

- | The clock

- | Communication circuits

• | The following items may be suppressed:

- | Battery wires

- | Ignition wires

• | After adding any suppression, inspect all vehicle systems (including non-audio related systems) for proper operation.

• | 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, use a test harness that includes filters and capacitors. Always verify the effectiveness and operation of the test harness before permanently installing a FIX.

• | Use one of the following recommended capacitor applications for an audible pop induced from a switching operation:

- | 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 ON position and the engine running, perform the following inspections:

- | Inspect the integrity of the ignition system, including the following conditions. Refer to Ignition System.

• | Proper spark plug wire routing

• | No misfiring

• | Other conditions

- | Inspect the integrity of the engine compartment grounds.

- | Inspect for malfunctioning relays, solenoids, or other components that may be inducing noise or poor reception.

- | Inspect the ground integrity of the complaint-causing component.

• | For noise or poor reception, perform the Antenna System Test. Repair any components as necessary.

### 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.

• | Ensure that all of the ground straps between the engine and the frame are clean and tight.

• | Use the following repairs:

1. | If noise is still present, inspect the charging system. Refer to Charging System Check Charging System

2. | If the charging system is functioning properly, acquire any available technical service bulletins on generator whine.

3. | Install a filter GM P/N 1224205 in the battery feed to the radio.

4. | If noise is not eliminated, install the filter using the following variations:

• | Install the filter with the single wire side toward the radio and the ground wire attached to a good ground.

• | Remove the ground to the filter.

• | Reverse the filter so that the two-wire side is toward the radio with the ground wire attached to a good ground.

• | Remove the ground from the filter.

5. | If the noise is still present, install another filter GM P/N 1224205 in the ignition feed to the radio. Use the same installation variations as listed above.

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.

6. | Remove any unneeded filters after the repair, before reassembling the vehicle.

### Antenna System Test

#### Antenna System Resistance Values

Ohmmeter Probe Points | Resistance
--- | ---
Important: Perform the following procedure before measuring the resistance of the antenna:

1. Remove the battery negative lead.
2. Zero the ohmmeter.

When measuring the resistance, carefully wiggle the tip (4) and the cable. If the readings in the following table are not obtained, replace a portion of the lead-in intermittent and the lead in.

The negative battery cable and the radio connection metal case (6) | 0-0.15 ohms
The negative battery cable and the antenna base (2) | 0-0.15 ohms
The radio connection metal case (6) and the antenna connection metal case (3) | 0-0.15 ohms
The radio connection metal case (6) and the antenna base (2) | 0-0.15 ohms
The negative battery cable and the radio connection tip (5) | ∞
The radio connection metal case (6) and the radio connection tip (5) | ∞
The radio connection metal case (6) and the antenna connection tip (4) | ∞
The radio connection metal case (6) and the antenna mast (1) | ∞
The negative battery cable and the antenna connection tip (4) | ∞
The negative battery cable and the antenna mast (1) | ∞
The negative battery cable and the antenna connection metal case (3) | 0-0.15 ohms

#### Lead-in Cable Resistance Values

Digital Multimeter Probe Points | Resistance
--- | ---
The radio connection tip (5) and the antenna mast (1) (RG-62 and RG-62M) | 0-3.5 ohms
The radio connection tip (5) and the antenna mast (1) (RG-58 and RG-59) | 0-0.2 ohms
The radio connection tip (5) and the radio connection metal case (6) | Infinite
The radio connection tip (5) and the antenna base (2) | Infinite
The radio connection tip (5) and the antenna connection metal case (3) | Infinite
The antenna connection tip (4) and the antenna connection metal case (3) | Infinite
The radio connection tip (5) and the antenna connection tip (4) (RG-62 and RG-62M) | 0-3.5 ohms
The radio connection tip (5) and the antenna connection tip (4) (RG-58 and RG-59) | 0-0.2 ohms