Diagnostic Instructions
DTC Descriptor
DTC B1440: Power Mode Master Input Circuits Mismatch
Circuit/System 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:
If the BCM detects a change in the ignition mode switch data, it sends a class 2 message to RCDLR requiring authentication for that change.
Conditions for Running the DTC
Voltage supplied to the module is in the normal operating voltage range of 9-16 volts.
Conditions for Setting the DTC
| • | 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
| • | 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. |
Reference Information
Schematic Reference
Connector End View Reference
Component Connector End Views
Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References
for scan tool information.
Circuit/System Verification
BCM
Ignition ON, observe the scan tool power mode parameter. Switch the vehicle from off, ignition on engine off, and start. The mode should change from off/Accessory/Run/Crank Request.
RCDLR
Ignition ON, observe the scan tool ignition mode switch parameter. Switch the vehicle from off, ignition on engine off, and start. While pressing the START button one time, the parameter should read ACC/OFF. While pressing and holding the START button,
the parameter should read Crank. When the START button is not pressed the parameter should read Idle.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the ignition mode switch.
- Ignition OFF, test for less then 20 ohm of resistance between the ground circuit terminal F and ground.
| ⇒ | If greater then the specified range, test the ground circuit for an open/high resistance. |
- Ignition OFF, test for less then 130 ohm of resistance between the ground circuit terminal K, and ground.
| ⇒ | If greater then the specified range, test the ground circuit for an open/high resistance. |
- Ignition ON, With a DMM, test for B+ between the data signal circuit terminal E, and ground.
| ⇒ | If less then the specified value, test the data signal circuit for a short to ground or open/high resistance. If circuit test normal, replace the BCM. |
- With a DMM test for B+ between the data signal circuit terminal A, and the ground.
| ⇒ | If less then the specified value, test the data signal circuit for a short to ground or open/high resistance. If circuit test normal, replace the RCDLR. |
- If all circuits test normal, replace the ignition mode switch.
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
Control Module References
for BCM or RCDLR replacement, setup, and programming
