GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1998 🢒 Sonoma Pickup - 2WD 🢒 Body and Accessories 🢒 Lighting Systems 🢒 Headlamps Inoperative - One Lamp

Headlamps Inoperative - One Lamp Envoy

Step

Action

Value(s)

Yes

No

1

Did you perform the Headlight System Check?

--

Go to Step 2

Go to Headlight System Check

2
  1. For the LH headlamp, connect a test lamp between the following components:
    2. • Ground
    • Both exposed test points on the rear of the LT LOW fuse
  2. For the RH headlamp, connect a test lamp between the following components:
    3. • Ground
    • Both exposed test points on the rear of the RT LOW fuse

Does the test lamp light on both sides of the fuse?

--

Go to Step 4

Go to Step 3

3
  1. For the LH headlamp, locate and repair a short to ground in CKT 712 (YEL).
  2. For the RH headlamp, locate and repair a short to ground in CKT 312 (TAN/WHT).
  3. Replace the LT/RT LOW fuse.

Is the repair complete?

--

Go to Headlight System Check

--

4
  1. Disconnect the inoperative headlamp ballast connector.
  2. For the LH headlamp, connect a test lamp between the following components:
    3. • Ground
    • CKT 712 (YEL)
  3. For the RH headlamp, connect a test lamp between the following components:
    4. • Ground
    • CKT 312 (TAN/WHT)
  4. Turn the headlamp switch to the HEAD position.

Does the test lamp light?

--

Go to Step 8

Go to Step 5

5
  1. Inspect the UBEC connector C4 for damaged or corroded terminals.
  2. Repair any damaged or corroded terminals.

Did you perform a repair?

--

Go to Headlight System Check

Go to Step 6

6

If the UBEC connections are OK, perform the following repairs:

    • For the LH headlamp, locate and repair an open in CKT 712 (YEL)
    • For the RH headlamp, locate and repair an open in CKT 312 (TAN/WHT).

Did you perform a repair?

--

Go to Headlight System Check

Go to Step 7

7

Replace the UBEC.

Is the repair complete?

--

Go to Headlight System Check

--

8
  1. Connect the following components to the J 39200 DMM:
    2. • Test leads
    • Test lead adapters
  2. Connect the leads of the J 39200 DMM together.
  3. Set the J 39200 DMM to the ohms scale.
  4. Record the ohms value.
  5. Subtract the value from all resistance readings. If the meter you are using has a zeroing function, zero the meter.

    6. Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

  6. Disconnect the battery cables.
  7. For the LH headlamp, connect a J 39200 DMM between CKT 150 (BLK) and ground
  8. For the RH headlamp, connect a J 39200 DMM between CKT 250 (BLK) and ground.

Is the resistance less than the specified value?

1.0 ohms

Go to Step 10

Go to Step 9

9
  1. For the LH headlamp, locate and repair an open in CKT 150 (BLK).
  2. For the RH headlamp, locate and repair an open in CKT 250 (BLK).

Is the repair complete?

--

Go to Headlight System Check

--

10

Use a 10A fuse in order to substitute the LT LOW or RT LOW fuse in the UBEC.

Did you substitute the fuse?

--

Go to Step 11

--

11
  1. For the LH headlamp, connect a fused jumper with at least a 20A fuse between the following components for a period of 5 seconds:
    2. • CKT 712 (YEL)
    • CKT 150 (BLK)
  2. For the RH headlamp, connect a fused jumper with at least a 20A fuse between the following components for a period of 5 seconds:
    3. • CKT 312 (TAN/WHT)
    • CKT 250 (BLK)

Did the 10A fuse in the UBEC open within 5 seconds?

--

Go to Step 15

Go to Step 12

12
  1. Immediately disconnect the jumper wire.
  2. For the LH headlamp, connect a fused jumper with at least a 20 amp fuse between the following components:
    3. • CKT 712 (YEL)
    • Ground
  3. For the RH headlamp, connect a fused jumper with at least a 20 amp fuse between the following components:
    4. • CKT 312 (TAN/WHT)
    • Ground

Did the 10A fuse in the UBEC for this low beam circuit open within 5 seconds?

--

Go to Step 13

Go to Step 14

13
  1. For the left headlamp, locate and repair high resistance in CKT 150 (BLK).
  2. For the right headlamp, locate and repair high resistance in CKT 250 (BLK).

Is the repair complete?

--

Go to Headlight System Check

--

14
  1. Immediately disconnect the jumper wire.
  2. For the left headlamp, locate and repair high resistance in CKT 712 (YEL).
  3. For the right headlamp, locate and repair high resistance in CKT 312 (TAN/WHT)

Is the repair complete?

--

Go to Headlight System Check

--

15

Reinstall the 20A fuse in the UBEC.

Is the repair complete?

--

Go to Step 16

--

16
  1. Replace the ballast with a good ballast. Refer to High Intensity Discharge Headlamp Ballast Replacement . If available, use a ballast from the parts department. Otherwise, use the good ballast from the other side of the vehicle.
  2. Turn the headlamp switch to the HEAD position.

Does the inoperative headlamp light?

--

Go to Step 17

Go to Step 18

17
  1. Install the ballast. Refer to High Intensity Discharge Headlamp Ballast Replacement .
  2. Re-assemble the vehicle.

Is the repair complete?

--

Go to Headlight System Check

--

18

Replace the starter/arc tube assembly for the inoperative headlamp. Refer to High Intensity Discharge Headlamp Starter/Arc Tube Replacement .

Is the repair complete?

--

Go to Headlight System Check

--