B1440

DTC B1440

Circuit Description
The body control module (BCM) is the power mode master and the remote control door lock receiver (RCDLR) is the backup power mode master. Both modules receive information regarding ignition mode switch position from the ignition mode switch. The ignition mode switch will be monitored only with battery voltage at or above 7 volts to prevent invalid input readings during low voltages encountered during vehicle cranking.
Four modes are discernible:

^ Inactive
^ Start active
^ Off active
^ Short detect

If the BCM detects a change in the ignition mode switch data, sends a class 2 message to RCDLR requiring authentication for that change.

DTC Descriptors
This diagnostic procedure supports the following DTC:
DTC B1440 Power Mode Master Input Circuits Mismatch

Conditions for Running the DTC
The only requirements are voltage and ground.

Conditions for Setting the DTC
The RCDLR sets this code if any of the following conditions occur:

^ The RCDLR mode data input is active for more than 60 seconds, without seeing the corresponding message from the BCM.
^ The RCDLR detects a short to ground on its mode data input circuit, for more than 60 seconds.

Action Taken When the DTC Sets
One of the following scenarios may take place:

^ If the RCDLR senses a change on its ignition mode data input two times in a row, but does not receive the corresponding message from the BCM, the RCDLR will enable the backup power mode. The backup power mode will be changed accordingly to signal sensed.
^ If the RCDLR receives a message from the BCM, indicating that a switch has been pressed, without sensing the change itself, backup power moding will be disabled for the current ignition cycle.

Conditions for Clearing the DTC
^ A current DTC clears when the malfunction is no longer present.
^ A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Diagnostic Aids
The setting of this DTC can be caused by various failures:

^ The RCDLR malfunction
^ The BCM malfunction
^ The ignition mode switch malfunction
^ The ignition mode data input and ground circuits for either the RCDLR or the BCM

Test Description
The numbers below refer to the step numbers on the diagnostic table.

2. This step checks for a proper reading of the ignition mode switch by the BCM.
11. This step checks for a proper reading of the ignition mode switch by the RCDLR.