For 1990-2009 cars

### Circuit Description

The BCM Diagnostic Check is an organized approach to identify problems associated with the BCM. This check must be the starting point for any BCM complaint, and will direct you to the next logical step in diagnosing the complaint. The BCM is a very reliable component and is not likely the cause of the malfunction. Most system complaints are linked to faulty wiring and connectors, and occasionally to components. Understanding the computer system and using the tables correctly will reduce diagnostic time and prevent unnecessary parts replacement.

### Diagnostic Aids

• | The following conditions may result in an intermittent operation of the BCM with no DTC stored:

- | Any condition which results in the interruption of power to the BCM

- | Out of range battery or ignition voltage

Specification
Normal BCM operating voltage: 9.0-16.0 V

- | A loose or damaged ground(s)

• | An intermittent failure in the electronic system may be very difficult to detect and to accurately diagnose. A good description of the complaint may be very useful in locating an intermittent malfunction. Faulty electrical connections or wiring causes most intermitting problems. When an intermitting condition is suspected, check the suspected circuits for the following conditions:

- | Poor mating of connector halves or backed out terminals

- | Improperly formed or damaged terminals

- | Wire chafing

- | Poor wire to terminal connections

- | Dirty or corroded terminals

- | Damage to connector bodies

• | If the DTC is a history DTC, the problem may be intermittent. Perform the tests shown while moving related wiring and connectors. This can often cause the malfunction to occur. Perform a thorough inspection of all related wiring and connectors pertaining to the history DTC stored.

• | Exit all scan tool tests before cycling the ignition OFF to ON unless the scan tool instructions direct otherwise. Follow the operating instructions in the scan tool operator's manual. Failure to follow these instruction may set DTCs, cause vehicle system malfunctions, set false DTCs, or cause scan tool malfunctions.

### Test Description

The numbers below refer to the step numbers on the diagnostic table:

1. This test determines if communication can be established between the scan tool and the BCM.

2. This step tests for current DTCs stored in the BCM.

3. This test determines if communication can be established with other modules connected to the Class 2 serial data line.

4. This step inspects the BCM power fuse in order to aid in location and diagnosis, refer to Body Control System Schematics .

5. This step tests for an open in the BCM power circuit.

6. This step tests the BCM ground circuit for an open.

7. This step tests for an open in the Class 2 serial data circuit.

#### BCM Diagnostic System Check

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 |

1. Turn OFF the ignition switch.
2. Install a scan tool.
3. Turn ON the ignition switch.
4. Attempt to establish communication with the BCM.

Does the scan tool communicate with the BCM?

--

Go to Step 2

Go to Step 3

2 | Select BCM DTC function with the scan tool. Are any current DTCs stored? | -- | Go to Diagnostic Trouble Code (DTC) List/Type | Go to Step 14
3 | Attempt to establish communication with the other systems connected to the same serial data line. Refer to Body Control System Schematics . Does the scan tool communicate with the other systems? | -- | Go to Step 4 | Go to Scan Tool Does Not Communicate w/Class 2 Data Line
4 | Inspect fuse V1 located in the power distribution fuse block. Is the fuse open? | -- | Go to Step 9 | Go to Step 5
5 |

1. Turn OFF the ignition switch.
2. Disconnect BCM connector C1.
3. Measure the voltage at terminal B3 (RED).

Is the voltage within the specified range?

10-13 V

Go to Step 6

Go to Step 11

6 |

1. Disconnect BCM connector C2.
2. Measure the resistance to ground at terminal C01 (BLK).

Is the resistance within the specified range?

0-5 ohms

Go to Step 7

Go to Step 12

7 | Test for continuity between BCM connector C2 terminal B9 (BRN/WHT) and DLC connector terminal 2. Is there continuity? | -- | Go to Step 8 | Go to Step 10
8 | Important: Perform the set up procedure for the BCM. Replace the BCM. Refer to Body Control Module Replacement . Is the replacement complete? | -- | Go to Step 13 | --
9 | Locate and repair the short to ground in CKT A910 (RED). Is the repair complete? | -- | Go to Step 13 | --
10 | Locate and repair the open circuit between the DLC connector terminal 2 and BCM terminal B9. Is the repair complete? | -- | Go to Step 13 | --
11 | Locate and repair the open in the BCM power circuit. Is the repair complete? | -- | Go to Step 13 | --
12 | Locate and repair the open in the BCM ground circuit. Is the repair complete? | -- | Go to Step 13 | --
13 |

1. Connect or install any connectors or components that were disconnected or removed in previous steps.
2. Install the scan tool in order to verify communication with the BCM.

Does the scan tool communicate with the BCM?

--

Go to Step 2

Go to Step 3

14 | Test the operation of the door locks by locking and unlocking the doors. Do the door locks operate properly? | -- | Go to Step 15 | Go to Power Door Locks System Check in Doors
15 | Press and release the trunk lid release button. Does the trunk lid release? | -- | Go to Step 16 | Go to Rear Compartment Lid Release Inoperative in Body Rear End
16 | Press and release the fuel tank filler door release button. Does the fuel tank filler door release? | -- | Go to Step 17 | Go to Fuel Filler Door Release Inoperative in Body Rear End
17 |

1. Deactivate the twilight sentinel feature (an indicator light in the OFF button will be On).
2. Shift the transmission into the DRIVE gear in order to verify the DRL operation.
3. Shift the transmission into the PARK gear.
4. Rotate the headlamp switch knob clockwise to the middle position in order to verify the parklamp operation.
5. Rotate the knob to the next position in order to verify the low beams operation.
6. Activate the high beams by pushing the turn signal lever away from you in order to verify the high beams operation.
7. Pull the turn signal lever towards you in order to verify the Flash-To-Pass feature.
8. Rotate the headlamp switch knob counterclockwise to the OFF position.

Do all lamps and features operate properly?

--

Go to Step 18

Go to Headlight System Check in Lighting Systems

18 |

1. Activate the twilight sentinel feature by pressing and releasing the OFF button (an indicator light in the button will be Off).
2. Rotate the control dial all the way up.
3. Cover the light sensor located in the top center dash area.
4. Verify twilight sentinel operation (low beams and parklamps illuminated).

Is the twilight sentinel operating properly?

--

Go to Step 19

Go to Twilight Sentinel Inoperative in Lighting Systems

19 |

1. Turn the ignition to the OFF position and remove the key.
2. From the outside of the vehicle, operate the RKE transmitter through all button positions (door lock/unlock, trunk lid and fuel filler door releases).

Is the transmitter operating properly?

--

System OK

Go to Diagnostic System Check - Remote Keyless Entry in Keyless Entry