GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

  1. Using a test light, backprobe between connector C240 terminal M to ground.
  2. Turn the ignition switch on.

Does the test light illuminate?

--

Go to Step 2

Go to Step 7

2

  1. Disconnect C240.
  2. Connect a DMM between C240 (female side) terminal M and terminal P.
  3. Press each of the radio control switch buttons one at a time.
  4. Compare the approximate resistance values to the list below:
  5. • Volume Up: 6652ohms
    • Volume Down: 13632ohms
    • Source: 4282ohms
    • PSCAN: 3102ohms
    • Mute: 2387ohms
    • AMFM: 1912
    • Seek Down: 1564ohms
    • Seek Up: 1270ohms

Do all the resistance values approximately equal those above?

--

Go to Step 4

Go to Step 3

3

  1. Disconnect the radio control switch.
  2. Connect a DMM between the radio control switch harness connector terminal A and terminal D.
  3. Press each of the radio control switch buttons, one at a time.
  4. Compare the approximate resistance values to the list below:
  5. • Volume Up: 6652ohms
    • Volume Down: 13632ohms
    • Source: 4282ohms
    • PSCAN: 3102ohms
    • Mute: 2387ohms
    • AMFM: 1912
    • Seek Down: 1564ohms
    • Seek Up: 1270ohms

Do all the resistance values approximately equal those above?

--

Go to Step 6

Go to Step 8

4

  1. Using a test light, backprobe between the radio harness connector terminal E6 to ground.
  2. Turn the ignition switch on.

Does the test light illuminate?

--

Go to Step 9

Go to Step 5

5

Using a DMM, measure the resistance between the radio harness connector terminal E6 and ground.

Is the resistance measured same as the specified value?

Go to Step 6

Go to Step 10

6

Inspect circuit 1796.

Is there a poor connection or open in circuit 1796?

--

Go to Step 11

Go to Step 12

7

Repair poor connection or open in circuit 43.

Is the repair complete?

--

Go to Diagnostic System Check - Radio/Audio System

--

8

Replace the radio control switch. Refer to Rear Seat Audio Control Replacement for service procedure.

Is the repair complete?

--

Go to Diagnostic System Check - Radio/Audio System

--

9

Repair short to B+ on circuit 1796.

Is the repair complete?

--

Go to Diagnostic System Check - Radio/Audio System

--

10

Repair short to ground in circuit 1796.

Is the repair complete?

--

Go to Diagnostic System Check - Radio/Audio System

--

11

Repair poor connection or open in circuit 1796.

Is the repair complete?

--

Go to Diagnostic System Check - Radio/Audio System

--

12

Replace the radio. Refer to Radio Replacement for service procedure.

Is the repair complete?

--

Go to Diagnostic System Check - Radio/Audio System

--