Diagnostic Instructions

•	Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

•	Review Strategy Based Diagnosis for an overview of the diagnostic approach.

•	Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC B1370 01

Control Module Ignition On and Start Circuit Short to Battery

DTC B1370 04

Control Module Ignition On and Start Circuit Open

DTC B1380 01

Control Module Ignition Accessory Circuit Short to Battery

DTC B1380 04

Control Module Ignition Accessory Circuit Open

DTC B1441 01

Control Module Ignition Off, Run, and Start Circuit Short to Battery

DTC B1441 04

Control Module Ignition Off, Run, and Start Circuit Open

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
B+	B1370 04, B1380 04	B1370 04, B1380 04	-	-
5 V REF	-	1	-	-
Ignition Terminal 1	B1370 04, B1380 04	B1370 04, B1380 04	B1370 01	-
Ignition Terminal 3	B1370 04, B1380 04	B1380 04	B1380 01	-
Signal Terminal 4	B1370 04, B1380 04, B1441 04	B1441 04	B1441 01	-
1. Power Mode Mismatch

Circuit/System Description

The vehicle power mode master is the body control module (BCM). The ignition switch is a low current switch with multiple discrete circuits to the BCM. The BCM logic uses the ignition switch positions 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 power mode master serial data message does not match what the individual module can detect from its own connections.

The power mode master will activate relays and other direct outputs of the power mode master 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, B1441 01

Ignition switch is in the ACCESSORY position.

B1370 04

Ignition switch is in the RUN or CRANK positions.

B1380 01

Ignition switch is in the CRANK position.

B1380 04

Ignition switch is in the RUN or ACCESSORY positions.

B1441 04

Ignition switch is in the OFF, RUN, or CRANK positions.

Conditions for Running the DTC

B1370 01, B1370 04

Ignition switch is in the RUN or CRANK positions.

B1380 01, B1380 04

Ignition switch is in the RUN or ACCESSORY positions.

B1441 01, B1441 04

Ignition switch is in the CRANK position.

Conditions for Setting the DTC

B1370 01

Ignition circuit is shorted to voltage.

B1370 04

•	Ignition circuit is open.

•	Ignition, accessory, or off/run/crank circuit shorted to ground.

•	B+ circuit of the ignition switch is open or shorted to ground.

•	Ignition relay control circuit open, including relay coil and ground.

B1380 01

Accessory circuit is shorted to voltage.

B1380 04

•	Accessory circuit is open.

•	Ignition, accessory, or off/run/crank circuit shorted to ground.

•	B+ circuit of the ignition switch is open or shorted to ground.

B1441 01

Off/run/crank signal circuit is shorted to voltage.

B1441 04

Off/run/crank signal circuit is open.

Actions Taken When the DTC Sets

•	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

•	The condition responsible for setting the DTC no longer exists.

•	A history DTC will clear once 50 consecutive malfunction-free ignition cycles have occurred.

Reference Information

Schematic Reference

•	Body Control System Schematics

•	Power Distribution Schematics

•	Power Moding Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Power Mode Description and Operation

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

With a scan tool, access Power Mode data display list and compare all parameters listed with the corresponding ignition key position. The Power Mode Parameters table below illustrates the correct state of these input parameters in correspondence to the S39 ignition switch position. The circuits which the individual parameters are related to are in parentheses.

Power Mode Parameters

Ignition Switch Position	5 V IGN (Ignition Switch, Terminal 4 and 6)	Accessory (Ignition Switch, Terminal 3)	Run/Crank (Ignition Switch, Terminal 1)
Off Key Out	Key Out/ACC	Inactive	Inactive
Off Key IN	Key In/Off	Inactive	Inactive
Accessory	Key Out/ACC	Active	Inactive
Run	Run	Active	Active
Starting	Crank Request	Inactive	Active

Circuit/System Testing

1.	Disconnect the X1 harness connector at the S39 ignition switch.

2.	Verify that a test lamp illuminates between the B+ circuit terminal 2 and ground.

3.	If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the ignition circuits listed below for a short to ground.

•

Note To help isolate a short to ground, it may be necessary to disconnect modules that are connected to the following circuits: terminal 1

•

terminal 3

•

terminal 4

•

terminal 6

4.	Connect the harness connector at the S39 ignition switch.

5.	Ignition OFF, key out, disconnect the X3 harness connector at the K9 BCM. Verify that a test lamp does not illuminate between the ignition circuit terminals listed below and ground:

•

terminal 5

•

terminal 6

•

terminal 15

•

terminal 22

6.	If the test lamp illuminates, test the ignition circuits for a short to voltage. If the circuit tests normal, replace the S39 ignition switch.

7.	Ignition in the ACCESSORY position, verify that a test lamp illuminates between the terminal 5 and ground.

8.	If the test lamp does not illuminate, test the ignition circuit for an open/high resistance. If the circuit tests normal, replace the S39 ignition switch.

9.	Ignition in the CRANK position, verify that a test lamp illuminates between terminal 6 and ground.

10.	If the test lamp does not illuminate, test the ignition circuit for an open/high resistance. If the circuit tests normal, replace the S39 ignition switch.

11.	If all of the circuits test normal, replace the K9 BCM.

Component Testing

Ignition Switch

1.	Ignition OFF, disconnect the harness connector at the S39 ignition switch.

2.	Verify the resistance between the terminals listed below match for each S39 ignition switch position.

3.	If not the specified value, replace the S39 ignition switch.

Resistance Test

S39 Ignition Switch Position	Terminals 1 and 2	Terminals 2 and 3	Terminals 2 and 4	Terminals 2 and 6	Terminals 4 and 6
Off Key Out	Infinite	Infinite	Infinite	Infinite	Infinite
Off Key IN	Infinite	Infinite	< 5.0 Ω	Infinite	Infinite
Accessory	Infinite	< 5.0 Ω	Infinite	Infinite	Infinite
Run	< 5.0 Ω	< 5.0 Ω	Infinite	Infinite	< 5.0 Ω
Starting	< 5.0 Ω	Infinite	Infinite	Infinite	1275-1325 Ω

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

Control Module References for BCM replacement, setup, and programming