GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1999 🢒 Catera 🢒 DTC 🢒 DTC 18, 19, and 20

LH, RH and Inside Rear View Mirrors
Object Number: 246082 Size: LF
Power Door Systems Components
Heated Mirror Circuit Description
Outside Rearview Mirror Schematics

Circuit Description

The driver seat adjuster memory module monitors the reference voltage of all three rear view mirror potentiometers using terminals 4 and 5 of the driver seat adjuster memory module connector C2. The normal voltage reading should be +5V. If the voltage reading is not in the normal range, the driver seat adjuster memory module sets DTCs 18, 19 and 20.

Conditions for Setting the DTCs

DTC 18, 19, and 20 will set if:

    • there is a short to voltage in any of the circuits related to terminals 4 and 5 of the driver seat adjuster memory module connector C2.
    • there is a short to ground or an open in any of the circuits related to terminals 4 and 5 of the driver seat adjuster memory module connector C2.
    • there is a failure within the LH or RH outside rear view or the inside rear view mirror potentiometers.
    • there is an internal failure within the driver seat adjuster memory module.

Action Taken When the DTCs Set
    • The driver seat adjuster memory module will store DTCs 18, 19 and 20.
    • The automatic adjustment of all three rear view mirrors is blocked.
    • The adjustment speed of all three rear view mirror motors is not monitored (i.e. blocking end of the affected motor is not recognized).
    • The end stops of all three rear view mirror motors is not monitored (i.e. the affected motor is not switched off when it reaches its programmed end stop).
    • The position of all motors is not stored in the driver seat adjuster memory module.

Conditions for Clearing the DTCs
    • DTCs 18, 19 and 20 will clear when the conditions for the fault are no longer present.
    • DTCs 18, 19 and 20 can be cleared by using the scan tool.

Diagnostic Aids
    • Check for an open, high resistance, short to ground or short to voltage in circuits FX75, FX60, FX65 and/or FX70.
    • Check for an open, high resistance, short to ground or short to voltage in circuits X75, X60, X65 and/or X70.
    • Check for loose connections and damaged connectors.

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. This step checks the voltage on circuits X75, X70, X65 and X60.

    2.

  2. This step checks the voltage on circuits FX75, FX70, FX65 and FX60

    3.

  3. This step checks the rear view mirrors motor potentiometers for an open or faulty resistance reading

All Three Rear View Mirrors Inoperative, DTCs 18, 19 and 20 Set

Step

Action

Value(s)

Yes

No

1

Was the Power Mirrors System Check performed?

--

Go to Step 2

Go to Outside Mirrors System Check .

2

  1. Disconnect the following connectors.
    2. • Inside rear view mirror connector
    •  RH outside rear view mirror connector
    • LH outside rear view mirror connector
  2. Use the DMM to measure the voltage between the following connector terminals and a known good ground.
    3. • Terminal 4 of the inside rear view mirror connector
    • Terminal 4 of the RH outside rear view mirror connector
    • Terminal 4 of the LH outside rear view mirror connector

Are all the measured voltages within the specified value?

+5V

Go to Step 4

Go to Step 3

3
  1. Locate an open, high resistance, a short to ground or short to voltage in circuits X70, X75, X60 and/or X65.
  2. Repair the open, high resistance, short to ground, or short to voltage in circuits X70, X75, X60 and/or X65.
  3. Replace the driver seat adjuster memory module if these circuits are OK. Refer to Memory Seat Control Module Replacement in Seats.

Is the repair or replacement complete?

--

Go to Step 8

--

4

Use the DMM to measure the resistance between the following connectors and a known good ground.

    • Terminal 5 of the inside rear view mirror connector
    • Terminal 5 of the RH outside rear view mirror connector
    • Terminal 5 of the LH outside rear view mirror connector

Are all the measured resistances within the specified value?

Less than 5ohms

Go to Step 6

Go to Step 5

5
  1. Locate an open, high resistance, short to ground or short to voltage in circuits FX70, FX75, FX60 and/or FX65.
  2. Repair the open, high resistance, short to ground or short to voltage in circuits FX70, FX75, FX60 and/or FX65.
  3. Replace the driver seat adjuster memory module if these circuits are OK. Refer to Memory Seat Control Module Replacement in Seats.

Is the repair or replacement complete?

--

Go to Step 8

--

6

Use the DMM to measure the resistance between the following terminals of the rearview mirror motor potentiometers.

    • Terminal 5 and terminal 4 of the inside rear view mirror motor
    • Terminal 5 and terminal 4 of the RH outside rear view mirror motor
    • Terminal 5 and terminal 4 of the LH outside rear view mirror motor

Are all the measured resistances within the specified values?

1.25K ohms for the inside rear view mirror

1.85K ohms for the outside rearview mirrors

Go to Step 8

Go to Step 7

7

Replace the rear view mirror motor potentiometer that does not meet the specified value. Refer to one of the following procedures.

    • For outside rear view mirror, refer to Outside Rearview Mirror Motor Replacement in Doors.
    • For inside rear view mirror, refer to Inside Rearview Mirror Replacement in Stationary Windows.

Is the repair complete?

--

Go to Step 8

--

8
  1. Connect all connectors and components that were disconnected.
  2. Program the driver seat adjuster memory module. Refer to Memory Seat Operation in Seats.
  3. Install the scan tool.
  4. Verify that there are no codes present.
  5. Also verify that all three rear view mirrors operate properly.

Do all three of the rear view mirrors operate properly?

--

System OK

Go to Step 1