For 1990-2009 cars

### Circuit Description

The remote control door lock receiver monitors serial communications between it and the Body Control Module (BCM) over the Class 2 data bus. Each valid button push message received by the Remote Control Door Lock Receiver (RCDLR) is sent to the BCM. Then the RCDLR expects a Class 2 acknowledgment message from the BCM.

### Conditions for Setting the DTC

DTC B2561 sets if the RCDLR does not receive an acknowledgment to the button push message from the BCM.

### Action Taken When the DTC Sets

Stores a DTC B2561 in the receivers memory.

### Conditions for Clearing the DTC

• | The conditions for the fault are no longer present.

• | The use of a scan tool.

• | A history DTC will clear after 50 consecutive ignition cycles if the condition for the fault is no longer present.

### Diagnostic Aids

• | 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.

• | If the related wiring and connectors prove to be good and DTC B2561 continues to set on a intermittent basis, suspect the BCM as a possible cause.

### Test Description

The following numbers refer to the step numbers in the diagnostic table:

1. Communication error codes or Class 2 serial data circuit problems need to be corrected before continuing on.

2. This test checks if the BCM has received and acknowledged the message to lock all doors from the transmitter.

3. If the BCM receives the message to lock all doors, most likely the circuit and BCM are operating properly, however, the problem may be intermittent. In Intermittent and Poor Connections or Diagnostic Aids are helpful hints to assist in diagnosis.

4. If the integrity of the circuit between the RCDLR and BCM tests OK, the most likely cause is the BCM.

#### DTC B2561 Class 2 No Response To Report Status

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the RKE System Check performed? | -- | Go to Step 2 | Go to RKE System Check
2 | Install a scan tool and check for BCM DTCs U1176, 1255, 1300, or 1301. Are any U codes present? | -- | Go to Body Control System | Go to Step 3
3 |

1. From the BCM menu select RFA to BCM INFORMATION.
2. Using one of the transmitters (FOB), lock all doors.

Does the scan tool display which FOB you used and which button was pressed (door lock) on the FOB?

--

Go to Step 4

Go to Step 5

4 | Problem is intermittent. Refer to Intermittent and Poor Connections or Diagnostic Aids. Was a problem found and repaired? | -- | Go to RKE System Check | --
5 |

1. Disconnect the connector from the Remote Control Door Lock Receiver (RCDLR).
2. Disconnect connector C1 from the Body Control Module (BCM).
3. Use a DMM to measure the resistance between RCDLR connector terminal B and BCM terminal B9.

Is the measured resistance within the specified value?

Less than 2 ohms

Go to Step 6

Go to Step 7

6 | Replace the BCM. Before replacing the BCM, check the integrity of all the power and ground circuits to the BCM. Refer to Body Control Module for the replacement procedure. Is the replacement complete? | -- | Go to RKE System Check | --
7 | Repair the open or high resistance in CKT XM832/834. Is the repair complete? | -- | Go to RKE System Check | --