Power Mode Mismatch
Power Mode Mismatch
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructionsprovides an overview of each diagnostic category.
DTC Descriptors
DTC B1370 01
- Device Ignition 1 (ON and START) Circuit Short to Battery
DTC B1370 06
- Device Ignition 1 (ON and START) Circuit Short to Ground or Open
DTC B1380 01
- Device Ignition ACCESSORY Circuit Short to Battery
DTC B1380 06
- Device Ignition ACCESSORY Circuit Short to Ground or Open
DTC B1440 00
- Power Mode Master Input Circuits Mismatch
DTC B1441 01
- Device Ignition OFF, RUN, and CRANK Circuit Short to Battery
DTC B1441 06
- Device Ignition OFF, RUN, and CRANK Circuit Short to Ground or Open
Diagnostic Fault Information
Circuit/System Description
The vehicle power mode master (PMM) is the body control module (BCM). The ignition switch is a low current switch with multiple discrete ignition switch signals to the PMM for determination of the power mode. The PMM receives the ignition switch signals, and additionally a reference voltage signal from the BCM, through the ignition switch, and back to the BCM. There are redundancies within the PMM system that can allow operation of certain subsystems when there are faults in the ignition switch circuits. Other information such as serial data input from other modules and DTCs is also used to determine what power mode signals and information is transmitted by the PMM. The BCM logic uses all this information to identify the operator's desired power mode and activate specific discrete signals, and serial data messages for the operation of different subsystems as necessary. Other modules which have switched voltage inputs may operate in a default mode if the PMM serial data message does not match what the individual module can detect from its own connections.
The PMM will activate relays and other direct outputs of the PMM as needed according to the calculated power mode. Some relays controlled by the BCM are switched ignition voltage outputs that are pass through circuits within the BCM directly from the ignition switch. If these circuits short to ground, the B+ circuit fuse to the ignition switch will open.
Conditions for Running the DTC
B1370 01
Ignition switch is in the OFF or ACC positions.
B1370 06, B1380 01, B1441 01, B1441 06
Ignition switch is in the START position.
B1380 06, B1440 00
Ignition switch is in the RUN position.
Conditions for Setting the DTC
B1370 01
Ignition 1 voltage circuit is shorted to voltage.
B1370 06
* Ignition 1 voltage circuit is open.
* B+ circuit of the ignition switch open or shorted to ground.
B1380 01
Accessory voltage circuit is shorted to voltage.
B1380 06
* Accessory voltage circuit is open.
* B+ circuit of the ignition switch open or shorted to ground.
B1440
BCM senses an open or short to voltage on the off/run/crank voltage circuit when both ignition accessory/run and ignition run/crank parameters are active.
BCM senses an open on the B+ circuit to the ignition switch while the engine is running. An open on the B+ circuit can be caused by a short to ground on any of the circuits listed below:
* B+
* Accessory voltage
* Run/crank ignition 1 voltage BCM terminal 19, X4
* Off/run/crank voltage
B1441 01
Off/run/crank voltage circuit is shorted to voltage.
B1441 06
Off/run/crank voltage circuit is open.
Actions Taken When the DTC Sets
* The BCM stores DTC to memory.
* The BCM operates in a fail-safe power mode dependent on the last valid power mode detected and the state of the engine run flag data on the serial data communications circuits.
* The other modules on the vehicle operate in a fail-safe power mode dependent on the last valid power mode transmitted by the BCM and the state of the engine run flag on the serial data communications circuits.
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
* A short to ground in the run/crank ignition circuit of the run crank relay will cause an open fuse to the ignition switch. DTC B1428 should be current.
* A short to ground in the accessory wake-up serial data circuit will cause an open fuse to the ignition switch. DTC U1814 should be current.
* The power modes and controls are determined using BCM logic. Comparing the Body Control Module Power Mode data display parameters listed in Circuit/System Verification will determine if there is a power mode fault.
Reference Information
Schematic Reference
* Power Distribution Schematics Power Distribution Schematics
* Power Moding Schematics Power Moding Schematics
Connector End View Reference
Component Connector End Views Connector End Views By Name
Description and Operation
Power Mode Description and Operation Power Mode
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Programming and Relearningfor scan tool information
Circuit/System Verification
1. Verify that the following DTCs are not set: U1814, B1428.
• If either of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.
2. With a scan tool, access BCM, Power Mode data display list and compare all parameters listed with the corresponding ignition key position. The PMM Power Mode Parameters table below illustrates the correct state of these input parameters in correspondence to the ignition switch position. The circuits which the individual parameters are related to are in parentheses.
Circuit/System Testing
Note: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
1. Connect a test lamp between each fuse test terminal of the ignition switch B+ circuit fuse and ground. The test lamp should illuminate.
• If the test lamp does not illuminate, test the circuits listed below for a short to ground. If all circuits test OK, replace the BCM.
* B+ terminal 4
* Ignition terminal 2
* Ignition terminal 3
* Ignition terminal 5
* Ignition voltage terminal BCM terminal 21, X4
2. Disconnect the harness connector at the ignition switch.
3. Connect a test lamp between the B+ circuit terminal 4 and ground. The test lamp should illuminate.
• If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
Note: The ignition switch component test must be performed before proceeding with this test to verify the integrity of the switch.
4. Perform the ignition switch component test. Verify the switch passes the test.
• If the ignition switch does not test normal, replace the ignition switch.
5. Disconnect the X 1 harness connector at the BCM, test for less than 1.0 V between the following ignition circuit terminals of the BCM and ground.
* terminal 2
* terminal 4
* terminal 14
* terminal 21
• If greater than specified, test the circuit for a short to voltage.
6. Test for less than 1.0 Ohms between the BCM and the ignition switch on the ignition circuits listed below:
* terminal 2, X1 and ignition switch terminal 5
* terminal 4, X1 and ignition switch terminal 6
* terminal 14, X1 and ignition switch terminal 2
* terminal 21, X1 and ignition switch terminal 3
• If greater than specified, test the circuit for open/high resistance
7. If all circuits test normal, replace the BCM.
Component Testing
Ignition Switch
1. Ignition OFF, disconnect the harness connector at the ignition switch.
2. Verify the resistance between the terminals listed below match for each ignition switch position.
• If not the specified value, replace the ignition switch.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Control Module References Programming and Relearningfor BCM replacement, setup, and programming
* Ignition and Start Switch Replacement Service and Repair