For 1990-2009 cars

### 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+ - Terminal 2 | B1370 04, B1380 04 | B1370 04, B1380 04 | -- | --
Ignition - Terminal 3 | B1370 04, B1380 04 | B1380 04 | B1380 01 | --
Ignition - Terminal 4 | B1370 04, B1380 04, B1441 04 | B1441 04 | B1441 01 | --
Ignition - Terminal 1 | B1370 04, B1380 04 | B1370 04, B1380 04 | B1370 01 | --
Ignition - Terminal 6 | -- | 1 | -- | --
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, 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

1. Verify that DTC U1814 is not set.

⇒ | If DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle.

2. 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.

⇒ | If any parameters are incorrect in any key position, proceed to the Circuit/System Testing or Component Testing.

#### Power Mode Parameters

S39 Ignition Switch Position | Current Power Mode | Ign. Off/Run/Crank (S39 Ignition Switch, Terminal 4) | Ignition Accessory/Run (S39 Ignition Switch, Terminal 3) | Ignition Run/Crank (S39 Ignition Switch, Terminal 1)
--- | --- | --- | --- | ---
Off Key Out | Off | Key Out/ACC | Inactive | Inactive
Off Key IN | Off | Key In/Off | Inactive | Inactive
Accessory | Accessory | Key Out/ACC | Active | Inactive
Run | Run | Run | Active | Active
Start | Crank Request | Crank | Inactive | Active

### Circuit/System Testing

1. Disconnect the X1 harness connector at the S39 ignition switch.
2. Verify that a test lamp illuminates between B+ circuit terminal 2 and ground.

⇒ | 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

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

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

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

⇒ | 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.

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

⇒ | 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.

7. 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.

⇒ | 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
Start | < 5.0 Ω | Infinite | Infinite | Infinite | 1275-1325 Ω

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

Ignition and Start Switch Replacement

Control Module References for BCM replacement, setup, and programming.