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: Device Ignition 1 (ON and START) Circuit Short To Battery
DTC B1370 04: Device Ignition 1 (ON and START) Circuit Open
DTC B1380 01: Device Ignition ACCESSORY Circuit Short to Battery
DTC B1380 04: Device Ignition ACCESSORY Circuit Open
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 | Short to Ground | Open/High Resistance | Short to Voltage
--- | --- | --- | ---
B+ - Terminal 2 | B1370 04, B1380 04 | B1370 01, B1380 01, | B1370 01, B1380 01
Ignition - Terminal 3 | B1370 04 | B1370 01 | B1370 01
Ignition - Terminal 4 | B1380 04 | B1380 01 | B1380 01
Ignition - Terminal 5 | B1441 06 | B1441 06 | B1441 01

### 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

Voltage is between 9-16 volts.

### Conditions for Setting the DTC

• | The BCM detects a short to ground in the circuit.

• | The BCM detects a short to battery or an open in the circuit when the switch is in the OFF position.

### 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.

### Diagnostic Aids

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 to the scan tool values of the vehicle will determine if there is a power mode fault.

### Reference Information

#### Schematic Reference

• | 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 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.

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

#### PMM Power Mode Parameters

Ignition Switch Position | Power Mode | Run Relay Command (Terminal 5) | Ignition Switch Accessory Signal (Terminal 4) | Run/Crank Relay Command (Terminal 3)
--- | --- | --- | --- | ---
Operating Conditions: Drivers door open to disable RAP
Off Key Out | Off | Off | Inactive | Off
Off Key IN | Off | Off | Inactive | Off
Accessory | Accessory | Off | Active | Off
Run | Run | On | Active | On
Start | Crank Request | Off | Inactive | On

### Circuit/System Testing

Important: 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 ignition switch circuits listed below for a short to ground. If all circuits test OK, replace the BCM.

• | B+ terminal 2

• | Ignition terminal 4

• | Ignition terminal 3

• | Ignition terminal 5

2. Disconnect the harness connector at the ignition switch.
3. Connect a test lamp between the B+ circuit terminal 2 and ground. The test lamp should illuminate.

⇒ | If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.

Important: 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 X2 and X4 harness connectors at the BCM, test for less than 1.0 volt between the circuit terminals of the BCM listed below and ground:

• | Ignition terminal C8, X4

• | Ignition terminal D3, X4

• | Ignition terminal 56, X2

⇒ | If greater than specified, test the circuit for a short to voltage.

6. Test for less than 1.0 ohm between the BCM and the ignition switch on the circuits listed below:

• | Ignition terminal C8, X4 and 4

• | Ignition terminal D3, X4 and 3

• | Ignition terminal 56, X2 and 5

⇒ | If greater than specified, test the circuit for open/high resistance.

7. If all circuits test normal, replace the BCM.

### Component Testing

#### Ignition Switch

Using the Resistance Test below, check the resistance between the terminals of the ignition switch listed in each switch position listed.

⇒ | If any reading is other than specified, replace the ignition switch.

#### Resistance Test

Ignition Switch Position | Terminals 2 and 3 | Terminals 2 and 4 | Terminals 2 and 5 | Terminals 2 and 6 | Terminals 5 and 6
--- | --- | --- | --- | --- | ---
Off Key Out | Infinite | Infinite | Infinite | Infinite | Infinite
Off Key IN | Infinite | Infinite | < 5.0 Ohms | Infinite | Infinite
Accessory | Infinite | < 5.0 Ohms | Infinite | Infinite | Infinite
Run | < 5.0 Ohms | < 5.0 Ohms | Infinite | Infinite | < 5.0 Ohms
Start | < 5.0 Ohms | Infinite | Infinite | Infinite | 1275-1325 Ohms

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Ignition and Start Switch Replacement

• | Control Module References for module replacement, setup, and programming