For 1990-2009 cars

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics
1 | Did you perform the Lighting System Diagnostic System Check? | -- | Go to Step 2 | Go to Diagnostic System Check - Lighting Systems
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 the TS On/Off circuit of the BCM connector C1 and a good ground.

Is the measured resistance equal to the specified value?

Less than 2 ohms

Go to Step 3

Go to Step 10

3 |

1. Disconnect the headlamp automatic control ambient light sensor connector.
2. Use a DMM in order to measure the voltage between the + 5 volt reference circuit of the headlamp automatic control ambient light sensor connector and a good ground.

Is the measured voltage equal to the specified value?

+5 V

Go to Step 4

Go to Step 9

4 | Test for an open or high resistance or short to ground in the TS Day/Night circuit of the headlamp automatic control ambient light sensor. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 5
5 |

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

The status is determined by the input of the TS Day/Night circuit of the BCM connector C1. If the input is approximately B+, the status should be daytime. If the input is approximately 0 V, the status should be night time.

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

Go to Step 15

Go to Step 6

6 |

1. Disconnect the headlamp automatic control ambient light sensor connector.
2. Disconnect the BCM connector C1.
3. Connect a fused jumper between the + 5 volt reference circuit and the TS Day/Night circuit of the headlamp automatic control ambient light sensor connector.
4. Use a DMM in order to measure the voltage between the TS Day/Night circuit of the BCM connector C1 and a good ground.

Is the measured voltage equal to the specified value?

0 V

Go to Step 7

Go to Step 8

7 |

1. Remove the jumper from the headlamp automatic control ambient light sensor connector.
2. Use a DMM in order to measure the voltage between the TS Day/Night circuit of the BCM connector C1 and a good ground.

Is the measured voltage equal to the specified value?

12 V

Go to Step 14

Go to Step 11

8 | Test for a short to B+ in the TS Day/Night circuit of the BCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 13
9 | Test for an open or high resistance, short to ground, or short to B+ in the headlamp automatic control ambient light sensor + 5 volt reference circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 13
10 | Test for an open or high resistance in the TS On/Off circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 12
11 | Test for a short to ground in the TS Day/Night circuit of the BCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | --
12 | Replace the headlamp switch. Refer to Headlamp Switch Replacement . Did you complete the repair? | -- | Go to Step 16 | --
13 | 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 16 | --
14 | Replace the headlight automatic control light sensor l. Refer to Control Assembly Replacement in HVAC Systems-Automatic. Did you complete the repair? | -- | Go to Step 16 | --
15 | Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Did you complete the repair? | -- | Go to Step 16 | --
16 |

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?

--

System OK

Go to Step 2