GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1998 🢒 Sonoma Pickup - 2WD 🢒 Body and Accessories 🢒 Doors 🢒 Heated Mirrors Inoperative

Step

Action

Value(s)

Yes

No

1

Was the Defogger System Check performed?

--

Go to Step 2

Go to Defogger System Check in Stationary Windows

2

Inspect the HTDMIR fuse in the UBEC.

Is the fuse open?

--

Go to Step 3

Go to Step 14

3
  1. Remove the HTDMIR fuse.
  2. Using the J 39200 Digital Multimeter (DMM), connect the load side¹ of the HTDMIR fuse to battery ground.

Is the resistance less than the specified value?

4 ohms

Go to Step 4

Go to Defogger System Check in Stationary Windows

4

Disconnect connector C1 of the UBEC.

Does the resistance equal the specified value?

OL

Go to Step 6

Go to Step 5

5

Replace the UBEC.

Is the repair complete?

--

Go to Defogger System Check in Stationary Windows

--

6
  1. Reconnect connector C1 of the UBEC.
  2. Disconnect C501 (4-door) or C500 (2-door).
  3. Using the J 39200 DMM, connect between the male end of terminal P of C501 (4-door) or terminal A8 of C500 (2-door) to ground.

Is the resistance within the specified range?

8-10 ohms

Go to Step 7

Go to Step 9

7
  1. Disconnect the left outside rear view mirror connector.
  2. Using the J 39200 DMM, connect between terminal A and terminal H of the component end of the left outside rear view mirror connector.

Is the resistance within the specified range?

8-10 ohms

Go to Step 8

Go to Step 12

8

Repair the short to ground in CKT 2267 (ORN) between C501 and the left outside rear view mirror connector.

Is the repair complete?

--

Go to Defogger System Check in Stationary Windows

--

9
  1. Disconnect C601.
  2. Using the J 39200 DMM, connect between the male end of terminal P of C601 to ground.

Is the resistance within the specified range?

8-10 ohms

Go to Step 10

Go to Step 13

10
  1. Disconnect the right outside rear view mirror connector.
  2. Using the J 39200 DMM, connect between terminal A and terminal H of the component end of the right outside rear view mirror connector.

Is the resistance within the specified range?

8-10 ohms

Go to Step 11

Go to Step 12

11

Repair the short to ground in CKT 2267 (ORN) between C601 and the right outside rear view mirror connector.

Is the repair complete?

--

Go to Defogger System Check in Stationary Windows

--

12

Replace the heated mirror assembly.

Is the repair complete?

--

Go to Defogger System Check in Stationary Windows

--

13

Repair the short to ground in CKT 2267 (ORN) between underhood fuse block connector C1 and C601.

Is the repair complete?

--

Go to Defogger System Check in Stationary Windows

--

14
  1. Turn the ignition switch to the ON position.
  2. Operate the switches for the following devices:
    3. • The left front power window
    • The right front power window
    • The left front power door lock
    • The right front power door lock
    • The left front power mirror
    • The right front power mirror

Are any of these devices inoperative?

--

Go to Step 15

Go to Step 16

15
    • For the left side, locate and repair the open or high resistance in CKT 1850 (BLK) between the left outside rear view mirror and G202.
    • For the right side, locate and repair the open or high resistance in CKT 1050 (BLK) between the right outside rear view mirror and G205.

Is the repair complete?

--

Go to Defogger System Check in Stationary Windows

--

16
  1. Remove the defogger relay.
  2. Disconnect connector C1 of the UBEC.
  3. Using the J 39200 DMM, connect between the defogger relay terminal 87 and terminal F6 of connector C1 at the UBEC.

Is the resistance less than the specified value?

1 ohms

Go to Step 17

Go to Step 5

17
  1. Connect a fused jumper (10A fuse minimum) between the UBEC harness connector C1 terminal F6 and B+.
  2. Using a DMM, backprobe terminal A of the left outside rear view mirror or terminal A of the right outside rear view mirror.

Is there voltage present?

--

Go to Step 20

Go to Step 18

18

Using a DMM, backprobe terminal A of C501 (left front, 4-door), or terminal A8 of C500 (left front, 2-door), or terminal A of C601 (right front) to ground.

Is there voltage present?

--

Go to Step 20

Go to Step 19

19

Locate and repair the open or high resistance in CKT 2267 (ORN).

Is the repair complete?

--

Go to Defogger System Check in Stationary Windows

--

20

Using a DMM, backprobe terminal H of the left outside rear view mirror or terminal H of the right outside rear view mirror to ground.

Is there voltage present?

--

Go to Step 21

Go to Step 22

21

Locate and repair the open or high resistance in CKT 1850 (BLK) (left side) or CKT 1050 (BLK) (right side).

Is the repair complete?

--

Go to Defogger System Check in Stationary Windows

--

22

Replace the heated mirror assembly (left or right side).

Is the repair complete?

--

Go to Defogger System Check in Stationary Windows

--

¹The load side of the fuse is the terminal without battery voltage.