For 1990-2009 cars

## Twilight Sentinel Inoperative Buick

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Headlights System Check? | -- | Go to Step 2 | Go to Headlight System Check
2 |

1. Disconnect the Lamp Control Module (LCM) connector C2.
2. Connect a DMM from the LCM connector C2 cavity A5 (WHT) to ground.
3. Turn the ignition switch to RUN.

Is the voltage within the specified range?

10-15 V

Go to Step 3

Go to Step 7

3 |

1. Turn the ignition switch to the OFF position.
2. Connect a DMM from the LCM connector C2 cavity A6 (PPL) to cavity A4 (BLK/WHT).
3. Vary the twilight delay control from MIN to MAX.

Does the resistance vary within the specified range?

3.5K ohms-200K ohms

Go to Step 4

Go to Step 8

4 |

1. Cover the ambient light sensor.
2. Connect a DMM from the LCM connector C2 cavity A5 (WHT) to ground.

Is the resistance greater than the specified value?

31K ohms

Go to Step 5

Go to Step 11

5 |

1. Expose the ambient light sensor to a bright incandescent light.
2. Connect a DMM from the LCM connector C2 terminal A5 (WHT) to ground.

Is the resistance less than the specified value?

23K ohms

Go to Step 6

Go to Step 11

6 | Replace the LCM. Is the repair complete? | -- | Go to Headlight System Check | --
7 | Repair the open in CKT 39 (PNK) between S208 and the LCM. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Headlight System Check | --
8 | Inspect for an open or short to ground in CKT 1783 (PPL) between the LCM and the lamp dimmer switch. Refer to Testing for Continuity or Testing for Short to Ground in Wiring Systems. Is CKT 1783 OK? | -- | Go to Step 9 | Go to Step 14
9 | Inspect for an open in CKT 251 (BLK/WHT) between the LCM and the lamp dimmer switch. Refer to Testing for Continuity in Wiring Systems. Is CKT 251 OK? | -- | Go to Step 10 | Go to Step 14
10 | Replace the lamp dimmer switch. Refer to Instrument Panel Multifunction Switch Assembly Replacement in Instrument Panel, Gauges and Console. Is the repair complete? | -- | Go to Headlight System Check | --
11 | Inspect for a short to ground or open in CKT 278 (WHT) between the LCM and the ambient light sensor. Refer to Testing for Continuity or Testing for Short to Ground in Wiring Systems. Is CKT 278 OK? | -- | Go to Step 12 | Go to Step 14
12 | Inspect for an open in CKT 251 (BLK/WHT) between the ambient light sensor and S249. Refer to Testing for Continuity in Wiring Systems. Is CKT 251 OK? | -- | Go to Step 13 | Go to Step 14
13 | Replace the ambient light sensor. Refer to Sunload and Twilight Sentinel Sensor Replacement in Instrument Panel, Gauges and Console. Is the repair complete? | -- | Go to Headlight System Check | --
14 | Repair the suspect wiring. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Headlight System Check | --

## Twilight Sentinel Inoperative Pontiac/Oldsmobile

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Headlights System Check? | -- | Go to Step 2 | Go to Headlight System Check
2 |

1. Disconnect the Lamp Control Module (LCM) connector C1.
2. Connect a DMM from the LCM connector C1 cavity C (PNK) to ground.
3. Turn the ignition switch to RUN.

Is the voltage within the specified range?

10-15 V

Go to Step 3

Go to Step 8

3 |

1. Turn the ignition switch to the OFF position.
2. Disconnect the LCM connector C2.
3. Place the twilight sentinel switch in an ON position.
4. Connect a DMM from the LCM connector C2 cavity B8 (YEL/BLK) to ground.

Is the resistance less than the specified value?

5ohms

Go to Step 4

Go to Step 9

4 |

1. Connect a DMM from the LCM connector C2 cavity A1 (PPL) to ground.
2. Vary the twilight sentinel delay switch from MIN to MAX.

Did the resistance vary within the specified range?

3.5Kohms-200Kohms

Go to Step 5

Go to Step 10

5 |

1. Cover the ambient light sensor.
2. Connect a DMM from the LCM connector C2 cavity A2 (WHT) to ground.

Is the resistance greater than the specified value?

31K ohms

Go to Step 6

Go to Step 13

6 |

1. Expose the ambient light sensor to a bright incandescent light.
2. Connect a DMM from the LCM connector C2 cavity A2 (WHT) to ground.

Is the resistance less than the specified value?

23K

Go to Step 7

Go to Step 13

7 | Replace the LCM. Is the repair complete? | -- | Go to Headlight System Check | --
8 | Repair the open in CKT 3 (PNK) between S205 and the LCM. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Headlight System Check | --
9 | Inspect for an open in CKT 1784 (YEL/BLK) between the LCM and the headlamp switch. Refer to Testing for Continuity in Wiring Systems. Is CKT 1784 OK? | -- | Go to Step 11 | Go to Step 16
10 | Inspect for an open in CKT 1783 (PPL) between the LCM and the headlamp switch. Refer to Testing for Continuity in Wiring Systems. Is CKT 1783 OK? | -- | Go to Step 11 | Go to Step 16
11 | Inspect for an open in CKT 251 (BLK/WHT) between the headlamp switch and S249. Refer to Testing for Continuity in Wiring Systems. Is CKT 251 OK? | -- | Go to Step 12 | Go to Step 16
12 | Replace the headlamp switch. Refer to Instrument Cluster Trim Panel Replacement in Instrument Panel, Gauges and Console. Is the repair complete? | -- | Go to Headlight System Check | --
13 | Inspect for a short to ground or open in CKT 278 (WHT) wiring. Refer to Testing for Continuity or Testing for Short to Ground in Wiring Systems. Is CKT 278 OK? | -- | Go to Step 14 | Go to Step 16
14 | Inspect for an open in CKT 251 (BLK/WHT) between the ambient light sensor and S249. Refer to Testing for Continuity in Wiring Systems. Is CKT 251 OK? | -- | Go to Step 15 | Go to Step 16
15 | Replace the ambient light sensor. Refer to Sunload and Twilight Sentinel Sensor Replacement in Instrument Panel, Gauges and Console. Is the repair complete? | -- | Go to Headlight System Check | --
16 | Repair the suspect wiring. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Headlight System Check | --