For 1990-2009 cars
Body Control Module Components
Cell 51: SDM, Washer Solvent Level Sensor, Seat Belt and Park Brake Switches

### Circuit Description

This is a trouble code (both current and history) that indicates the automatic light control (ALC) parklamp relay control output is shorted to ground or open.

### Conditions for Setting the DTC

Meet all of the following conditions:

• | The ALC option is enabled and ignition one is active.

• | The ALC parklamp output is not active.

• | The ALC parklamp feedback is present for 5 seconds.

### Action Taken When the DTC Sets

• | Stores DTC B2587 in the body control module (BCM) memory.

• | The SERVICE VEHICLE SOON indicator will illuminate.

### Conditions for Clearing the DTC

• | The BCM goes to sleep and reinitializes with the fault cleared.

• | All the BCM history codes will be cleared after 10 ignition cycles (from OFF to RUN) with no current codes active during the 100 ignition cycles.

• | Use the Scan Tool .

### Diagnostic Aids

• | When the diagnostics direct you to take electrical measurements at the junction blocks, refer to Power Distribution Schematics in Wiring Systems for terminal assignments of the junction blocks.

• | If the DTC is a history DTC, the problem may be intermittent. Try performing the above tests while wiggling the wiring and connectors. This can often cause the malfunction to appear.

### Test Description

The numbers below refer to the numbers on the diagnostic table.

1. This step verifies proper operation of the ALC parklamp.

2. This step determines if a short to ground exists in CKT 1080 within the underhood junction block.

3. This step determines if a short to ground exists in CKT 1080 between the underhood junction block and the body control module (BCM).

4. This step determines if an open exists in CKT 1080 between the underhood junction block and the BCM.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the BCM system check performed? | -- | Go to Step 2 | Go to the Body Control Module System Check
2 |

1. Replace the ALC parklamp relay with a known good relay on the underhood junction block.
2. Use the Scan Tool in order to enable the ALC parklamp relay.

Does the ALC parklamp relay work correctly?

--

Go to Step 10

Go to Step 3

3 |

1. Reconnect the ALC parklamp relay on the underhood junction block.
2. Back out the underhood junction block connector C3 terminal B8, CKT 1080.
3. Use the J 39200 DMM in order to measure the voltage in CKT 1080 between the underhood wiring harness junction block connector C3 terminal B8 and ground.

Is the measured voltage at the specified value?

B+

Go to Step 5

Go to Step 4

4 | Replace the underhood junction block. Refer to Relay/Fuse Center Replacement in Wiring Systems. Is the repair complete? | -- | Go to Step 10 | --
5 |

1. Disconnect the BCM connector C1
2. Use the J 39200 DMM in order to measure the resistance in CKT 1080 between the BCM harness connector C1 terminal B1 and ground.

Is the measured resistance equal to the specified value?

∞

Go to Step 7

Go to Step 6

6 | Repair the short to ground in CKT 1080 between the BCM connector C1 terminal B1 and the underhood junction block connector C3 terminal B8 Refer to Wiring Repairs in Wiring Systems. is the repair complete? | -- | Go to Step 10 | --
7 | Use the J 39200 DMM in order to measure the resistance in CKT 1080 between the BCM harness connector C1 terminal B1 and the underhood junction block harness connector C3 terminal B8. Is the measured resistance within the specified range? | 0-2ohms | Go to Step 9 | Go to Step 8
8 | Repair the open in CKT 1080 between the BCM connector C1 terminal B1 and the underhood junction block connector C3 terminal B8. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Step 10 | --
9 | Replace the BCM. Refer to the following procedures:

• | Body Control Module Replacement

• | Body Control Module (BCM) Programming/RPO Configuration

Is the repair complete?

--

Go to Step 10

--

10 | Clear the DTCs from the memory. Are the DTCs cleared from the memory? | -- | Go to Body Control Module System Check | --