| Table 1: | PMM Power Mode Parameters |
| Table 2: | Resistance Test |
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 BatteryDTC B1370 06: Device Ignition 1 ON and START Circuit Open
Circuit/System Description
The body control module (BCM) monitors the ignition 1 signal from the ignition switch. When the vehicle operator places the ignition switch in the RUN or CRANK position, the switch supplies B+ to the BCM ignition 1 input terminal.
Conditions for Running the DTC
Voltage supplied to the module is in the normal operating voltage range of 9-16 volts.
Conditions for Setting the DTC
| • | The BCM detects a short to ground in the ignition 1 voltage circuit for greater then 10 seconds when the ignition switch is in RUN or CRANK. |
| • | The BCM detects a short to battery or an open in the ignition 1 voltage circuit for greater then 10 seconds 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 GMLAN 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 GMLAN 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. |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Power Mode Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information.
Circuit/System Verification
With a scan tool, compare all parameters listed below with the corresponding ignition key position. The PMM Power Mode Parameters table below illustrates the correct state of these input parameters (circuits) in correspondence to the ignition switch position. The circuits which the individual parameters are related to are in parentheses.
Ignition Switch Position | Current Power Mode | Ignition Off/Run/Crank (Off/Run Crank Voltage Circuit) | Ignition Accessory/Run (Accessory Voltage Circuit) | Ignition Run/Crank (Ignition 1 Voltage Circuit) |
|---|---|---|---|---|
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
Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
- Inspect for an open Ign Switch fuse. The fuse should be OK.
- Disconnect the harness connector at the ignition switch.
- Verify that a test lamp illuminates between the B+ circuit terminal 3 and ground.
- Perform the ignition switch component test. The test should pass.
- Ignition OFF, disconnect the X4 and X2 harness connector at the BCM, test for less than 1.0 volt between the following circuit terminals of the BCM and ground.
- Test for less than 1.0 ohm between the BCM and the ignition switch on the following circuit terminals.
- Test for infinite resistance between the ignition key resistor signal circuit terminal 4 of the BCM and ground.
- If all circuits test normal, replace the BCM.
| ⇒ | If the fuse is open, test the following circuits for a short to ground, if all circuits test OK, replace the BCM. |
| • | Battery positive voltage of the ignition switch |
| • | Accessory voltage |
| • | Off/Run/Crank voltage |
| • | Run/Crank voltage |
| • | Accessory wakeup serial data (BCM output) |
| • | Run/crank ignition 1 voltage (BCM output) |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for an open/high resistance. |
Important: The ignition switch component test must be preformed before proceeding with this test to verify the integrity of the switch.
| ⇒ | If the ignition switch fails, replace the ignition switch. |
| • | Off/Run/Crank voltage terminal 56 |
| • | 5 volt reference terminal 62 |
| • | Accessory voltage terminal C8 |
| • | Run/Crank voltage terminal D3 |
| ⇒ | If greater than specified, test the circuit for a short to voltage. |
| • | 5 volt reference, BCM terminal 62 and ignition switch terminal 6 |
| • | Off/Run/Crank voltage, BCM terminal 56 and ignition switch terminal 5 |
| • | Accessory voltage, BCM terminal C8 and ignition switch terminal 4 |
| • | Run/Crank voltage, BCM terminal D3 and ignition switch terminal 3 |
| ⇒ | If greater than specified, test the circuit for open/high resistance |
| ⇒ | If less than specified, test the signal circuit for a short to ground. |
Component Testing
Ignition Switch
- Ignition OFF, disconnect the harness connector at the ignition switch.
- Using the Resistance Test table below, check the resistance between the terminals of the ignition switch listed in each switch position.
Ignition Switch Position | Terminals 2 and 4 | Terminals 2 and 3 | 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 | < 5.0 Ohms | Infinite | Infinite | Infinite | Infinite |
Run | < 5.0 Ohms | < 5.0 Ohms | Infinite | Infinite | < 5.0 Ohms |
Start | Infinite | < 5.0 Ohms | Infinite | Infinite | 1275-1325 Ohms |
| ⇒ | If any reading is not as specified, replace the ignition switch. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.
| • | Control Module References for BCM replacement, setup, and programming |
