GM Service Manual Online
For 1990-2009 cars only

Poor Reception Diagnosis

Step

Action

Value

Yes

No

Refer to SIR Handling Caution in Cautions and Notices.: Electronic modules with an undiagnosed problem may cause Electromagnetic Interference (EMI). An EMI condition may cause radio reception interference.

To test for the presence of EMI in a module, systematically disconnect the electronic module connectors one at a time (turn the ignition switch to OFF before disconnecting each module) and note any improvement in radio reception. Do Not disconnect the Inflatable Restraint Sensing and Diagnostic Module (SDM).

1

  1. Verify the customer's complaint with the station(s) that are normally received in your area.
  2. Compare the complaint vehicle with a similar vehicle in the same locations that the concern is observed.

Does the radio reception of both vehicles perform the same?

--

Go to Step 2

Go to Step 3

2

Explain to customer the normal operation of the radio observed in both vehicles.

Is the explanation complete?

--

Go to Step 24

--

3

  1. Move vehicle outside away from any electrical interference such as electric motors, fluorescent lighting etc.
  2. Disconnect the coaxial cable from the radio.
  3. Temporarily mount a test antenna to the vehicle.
  4. Ground the antenna base and test the ground with a DMM before plugging the coax into the radio.
  5. Connect the coaxial cable.
  6. Do not hold the antenna in your hand.
  7. Turn radio on and tune to a strong radio station.

Does the reception improve?

--

Go to Step 4

Go to Step 5

4

Replace the Antenna assembly. Refer to Radio Antenna Replacement .

Is the replacement complete?

--

Go to Step 24

--

5

Refer to Checking Aftermarket Accessories in Wiring Systems.

Is any aftermarket wiring present?

--

Go to Step 6

Go to Step 8

6

Temporarily disconnect aftermarket wiring (both the battery and ground connections.

Does the radio reception improve?

--

Go to Step 7

Go to Step 8

7

Remove the aftermarket wiring.

Is the repair complete?

--

Go to Step 24

--

8

Compare the radio reception with the ignition switch in the following positions:

    • ACC
    • ON (engine not running)
    • ON (engine running)

Does the radio reception change with the key in the ON position (engine not running) or in the ON position (engine running)?

--

Go to Step 9

Go to Step 11

9

Was the radio reception degraded with the ignition key in the ON position (engine not running)?

--

Go to Step 11

Go to Step 10

10

Was the radio reception degraded with the ignition key in the ON position (engine running)?

--

Go to Step 11

Go to Step 13

11

Test for Electromagnetic Interference (EMI).

Was an EMI condition found in an electronic module?

--

Go to Step 12

Go to Step 13

12

Replace the faulty module.

Has the radio reception improved?

--

Go to Step 24

Go to Step 13

13

Using J 39200 set to measure AC voltage, connect the positive lead to the negative battery terminal and the negative lead of the DMM to a non-painted surface in the engine compartment.

Is the AC voltage less than the specified value?

25 mV

Go to Step 15

Go to Step 14

14

Repair the poor ground condition in one or more of the following ground connections:

    • G100
    • G101
    • G102
    • G103
    • G104
    • G105, G106
    • G109

Refer to Master Electrical Component List in Wiring Systems for locations.

Is the repair(s) complete?

--

Go to Step 21

--

15

Using J 39200 set to measure AC voltage, connect the positive lead to the negative battery terminal and the negative lead to a non-painted surface of the A-pillar.

Was the AC voltage less than the specified value?

25 mV

Go to Step 17

Go to Step 16

16

Repair the poor ground condition in one or more of the following ground connections:

    • G200
    • G201, G204
    • G202
    • G203
    • G204

Refer to Master Electrical Component List in Wiring Systems for locations.

Is the repair(s) complete?

--

Go to Step 21

--

17

Using J 39200 set to measure AC voltage, connect the positive lead to the negative battery terminal and the negative lead to a non-painted surface of the B-pillar.

Was the AC voltage less than the specified value?

25 mV

Go to Step 19

Go to Step 18

18

Repair the poor ground condition in one or more of the following ground connections:

    • G300
    • G301

Refer to Master Electrical Component List for locations.

Is the repair complete?

--

Go to Step 21

--

19

Using J 39200 set to measure AC voltage, connect the positive lead to the Negative battery terminal and the negative lead to a non-painted surface in the luggage compartment.

Was the AC voltage less than the specified value?

25 mV

Go to Step 22

Go to Step 20

20

Repair the poor ground connection at G400. Refer to Master Electrical Component List in Wiring Systems for locations.

Is the repair complete?

--

Go to Step 21

--

21

Has the radio reception improved?

--

Go to Step 24

Go to Step 22

22

Inspect for poor connections at the harness connector of the radio. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 24

Go to Step 23

23

Replace the radio. Refer to Radio Replacement .

Is the replacement complete?

--

Go to Step 24

--

24

Operate the system to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 3