GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 Envoy - 4WD 🢒 Body and Accessories 🢒 Entertainment 🢒 Amplifier Inoperative

Step

Action

Value(s)

Yes

No

1

Did you perform the Radio/Audio System Check?

--

Go to Step 2

Go to Radio/Audio System Check

2

Inspect the AMPF fuse 20 for an open.

Is the fuse open?

--

Go to Step 3

Go to Step 7

3

Test CKT 1340 (ORN) for a short to ground.

Is there a short to ground in CKT 1340 (ORN)?

--

Go to Step 4

Go to Step 6

4
  1. Disconnect the amplifier.
  2. Test CKT 1340 (ORN) for a short to ground.

Is there a short to ground in CKT 1340 (ORN)?

--

Go to Step 5

Go to Step 15

5

Repair the short to ground in CKT 1340 (ORN).

Is the repair complete?

--

Go to Radio/Audio System Check

--

6

Replace the AMPF fuse 20.

Is the replacement complete?

--

Go to Radio/Audio System Check

--

7

Test CKT 1340 (ORN) for an open circuit.

Is an open present in CKT 1340 (ORN)?

--

Go to Step 8

Go to Step 9

8

Repair the open in CKT 1340 (ORN).

Is the repair complete?

--

Go to Radio/Audio System Check

--

9

Test CKT 1050 (BLK) for an open circuit.

Is an open present in CKT 1050 (BLK)?

--

Go to Step 10

Go to Step 11

10

Repair the open in CKT 1050 (BLK).

Is the repair complete?

--

Go to Radio/Audio System Check

--

11
  1. Verify that the amplifier is connected.
  2. Turn the ignition switch to the ACC position.
  3. Turn the radio ON.
  4. Test CKT 145 (DK GRN) at the amplifier for voltage.

Is voltage present in CKT 145 (DK GRN)?

B+

Go to Step 15

Go to Step 12

12

Test CKT 145 (DK GRN) for an open circuit.

Is an open present in CKT 145 (DK GRN)?

--

Go to Step 13

Go to Step 14

13

Repair the open in CKT 145 (DK GRN).

Is the repair complete?

--

Go to Radio/Audio System Check

--

14

Service the radio. Refer to Radio Replacement .

Is service of the radio complete?

--

Go to Radio/Audio System Check

--

15

Important: The audio signal can be identified as a fluctuating AC voltage. Measure from the channel input cavity to the channel common ground cavity.

  1. Turn the volume control to mid-level.
  2. Test for audio signal input to the amplifier.
  3. Verify that the audio signal is present at one input.

Is the audio signal present at one input?

0-1.5 V AC

Go to Step 18

Go to Step 16

16
  1. Test for audio signal output at the radio.
  2. Verify that the audio signal is present at all outputs.

Is the audio signal present at all outputs?

0-1.5 V AC

Go to Step 17

Go to Step 14

17

Repair the harness.

Is the repair complete?

--

Go to Radio/Audio System Check

--

18
  1. Service the amplifier. Refer to Radio Speaker Amplifier Replacement .
  2. Test for open/shorted speakers.
  3. Test for open/shorted speaker harness.

Is service of the amplifier complete?

--

Go to Radio/Audio System Check

--