For 1990-2009 cars

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

1. Disconnect the BCM connector C1.
2. Turn the twilight sentinel switch to the ON position.
3. Use a DMM in order to measure the resistance between terminal A7 of the BCM connector C1 and a known good ground.

Is the measured resistance less than the specified value?

5 ohms

Go to Step 4

Go to Step 3

3 |

1. Locate an open or a high resistance in CKT AB810.
2. Repair the open or the high resistance in CKT AB810.
3. If CKT AB810 is OK, replace the headlamp switch. Refer to Headlamp Switch Replacement in Instrument Panel, Gauges and Console.

Did you complete the repair?

--

Go to Step 14

--

4 |

1. Disconnect the headlamp automatic control ambient light sensor connector.
2. Use the DMM in order to measure the voltage between terminal 1 of the headlamp automatic control ambient light sensor connector and known good ground.

Is the measured voltage equa to the specified value?

+5 V

Go to Step 6

Go to Step 5

5 |

1. Locate an open or a high resistance in CKT X812.
2. Repair the open or the high resistance in CKT X812.
3. If CKT X812 is OK, replace the heater and A/C control. Refer to Control Assembly Replacement in HVAC Systems.

Did you complete the repair?

--

Go to Step 14

--

6 |

1. Disconnect the heater and the A/C control connector C1.
2. Use the DMM in order to measure the resistance between terminal 3 of the headlamp automatic control ambient light sensor and terminal 2 of the heater and A/C control connector C1.

Is the measured resistance less than the specified value?

5 ohms

Go to Step 8

Go to Step 7

7 |

1. Locate an open or a high resistance in CKT F830.
2. Repair the open or the high resistance in CKT F830.

Did you complete the repair?

--

Go to Step 14

--

8 |

1. Install the scan tool.
2. Proceed to BCM inputs.
3. Select outside status.

The status is determined by the input to terminal A1 of the BCM connector C1. If the input is approximately B+, the status should be daytime. If the input is approximately O V, the status should be night time.

Does the scan tool tell you that it is either daytime or nighttime?

--

Go to Step 13

Go to Step 9

9 |

1. Disconnect the headlamp automatic control ambient light sensor connector.
2. Disconnect the BCM connector C1.
3. Connect a fused jumper between terminals 1 and 3 of the headlamp automatic control ambient light sensor connector.
4. Use the DMM in order to measure the voltage between terminal A1 of the BCM connector C1 and a known good ground.

Is the measured voltage equal to the specified value?

0 V

Go to Step 11

Go to Step 10

10 |

1. Locate a short to B+ in circuits XP830 and/or XP33.
2. Repair the short to B+ in circuits XP830 and/or XP33.
3. If these circuits are OK, replace the heater and the A/C control. Refer to Control Assembly Replacement in HVAC Systems.

Did you complete the repair?

--

Go to Step 14

--

11 |

1. Remove the jumper from the headlamp automatic control ambient light sensor connector.
2. Use the DMM in order to measure the voltage between terminal A1 of the BCM connector C1 and a known good ground.

Is the measured voltage equal to the specified value?

+12 V

Go to Step 13

Go to Step 12

12 |

1. Locate a short to ground, an open or a high resistance in circuits XP830 and/or XP33.
2. Repair the short to ground, open or the high resistance in circuits XP830 and/or XP33.
3. If these circuits are OK, replace the heater and the A/C control. Refer to Control Assembly Replacement in Instrument Panel, Gauges and Console.

Did you complete the repair?

--

Go to Step 14

--

13 | Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Did you complete the repair? | -- | Go to Step 14 | --
14 |

1. Connect all connectors and components that were previously disconnected.
2. Verify that the twilight sentinel system operates properly.

Does the twilight sentinel system operate properly?

--

Go to Headlight System Check

Go to Step 1