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 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 | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
B+ - Terminal 2 | B1370 06, B1380 06, B1440 00, U0100-U0299, 1, 2, 3, 4, 5 | B1370 06, B1380 06, B1440 00, U0100-U0299, 1, 2, 3, 4, 5 | -- | --
Ignition - Terminal 3 | B1370 06, B1380 06,U0100-U0299, 1, 2, 3, 4, 5 | B1380 06, 1, 5 | B1380 01, B3055 00, P0513 00, U0100-U0299, 1, 2, 4 | --
Ignition - Terminal 4 | B1370 06, B1380 006, B1423 03, B1440 00, B1441 06, P0513 00, U0100-U0299, 1, 2, 3, 4, 5 | B1440 00, B1441 06, 1 | B1441 01, P0513 00, U0100-U0299, 1, 2 | --
Ignition - Terminal 1 | B1370 06, B1380 06,U0100-U0299, 1, 2, 3, 4, 5 | B1370 06, B1380 06, U0100-U0299, 1 | B1370 01, B1440 00, P0575 00, P0856 00, U0100-U0299, 1, 2, 4 | --
Ignition - Terminal 6 | B1440 00, 1 | B1440 00, 1 | 1, 2 | --
Ignition Voltage - BCM Terminal 21 X4 | B1380 06, B1428 00, U0100-U0299, 1, 2, 3, 4 | P0628 00, 2, 4, 6 | B1440 00, 7 | --
Accessory Wakeup Serial Data, BCM Terminal 19 X4 | U0100-U0299, U1814 00, B1380 06, 1, 2, 3, 4, 5 | U0100-U0299, 4 | B3055 00, B3935 57 | --

1. Power Mode Mismatch. Different specific symptoms may occur depending on the vehicle operating conditions when the fault occurred.
2. Vehicle may not start.
3. The B+ circuit fuse to the ignition switch may be open.
4. May lose communication with other module(s).
5. The ignition switch may not return to the OFF position and the key may not come out of the ignition.
6. SIR system may retain DTC B1370 06 as current.
7. Vehicle will start and continue to run after the ignition key is removed.

### 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 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 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, B1380 01

Ignition switch is in the RUN or CRANK positions.

#### B1370 06, B1380 06

Ignition switch is in the RUN or ACCESSORY positions.

#### B1440 00

Ignition switch is in the RUN position.

#### B1441 01, B1441 06

Ignition switch is in the CRANK position.

### Conditions for Setting the DTC

#### B1370 01

Ignition circuit is shorted to voltage.

#### B1370 06

• | 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 06

• | 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.

#### B1440 00

BCM detects an open or short to voltage on the off/run/crank signal circuit when both ignition ACCESSORY/RUN and ignition RUN/CRANK parameters are active.

BCM detects an open on the B+ circuit to the ignition switch while the engine is running.

#### B1441 01

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

#### B1441 06

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

#### 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 or B1428 is not set.

⇒ | If any of the DTCs are set, refer to 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 BCM 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.

#### BCM Power Mode Parameters

Ignition Switch Position | Current Power Mode | Ign. Off/Run/Crank (Ignition Switch, Terminal 4) | Ignition Accessory/Run (Ignition Switch, Terminal 3) | Ignition Run/Crank (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 harness connector at the 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 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:

• | Ignition terminal 3

• | Ignition terminal 4

• | Ignition terminal 1

• | Ignition terminal 6

• | Ignition, BCM terminal 19, X4

• | Ignition, BCM terminal 21, X4

3. Connect the harness connector at the ignition switch.
4. Ignition OFF, key out, disconnect the X1 harness connector at the BCM. Verify that a test lamp does not illuminate between the ignition circuit terminals listed below and ground:

• | terminal 2

• | terminal 21

• | terminal 14

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

5. Ignition in the ACCESSORY position, verify that a test lamp illuminates between the terminal 21 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 ignition switch.

6. Ignition in the CRANK position, verify that a test lamp illuminates between terminal 14 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 ignition switch.

7. If all of the 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.

#### Resistance Test

Ignition Switch Position | Pins 1 and 2 | Pins 2 and 3 | Pins 2 and 4 | Pins 2 and 6 | Pins 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.