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 Descriptor
DTC B1370: Device Ignition 1 CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage |
|---|---|---|---|
B+ Terminal 4 | B1370, B1380, B1385 | B1370, B1380, B1385* | B1370, B1380, B1385 |
B+ Terminal 6 | B1370, B1380, B1385 | B1370, B1380, B1385* | B1370, B1380, B1385 |
Ignition Terminal 3 | B1370 | B1370 | B1370 |
Ignition Terminal 5 | B1380 | B1380 | B1380 |
Ignition Terminal 7 | B1385 | B1385 | B1385 |
* An open/high resistance in this circuit may not cause this DTC depending on the ignition switch position when the open/high resistance occurred. | |||
Circuit Description
The body control module (BCM), monitors the ignition 3, crank voltage, and ignition 1 circuits from the ignition switch. The BCM uses the sequence that the signals appear and their voltage levels to determine the power mode called for by the vehicle operator using the ignition switch. B+ is supplied by the BCM to the ignition switch over a discrete circuit. The ignition switch uses this voltage for power mode signal discrimination. When the operator places the ignition switch in the Run or Start position, the ignition 1 circuit is delivers the signal to the BCM.
Conditions for Running the DTC
| • | The BCM must be powered and must detect a change in the ignition switch circuit states. |
| • | The vehicles battery must be fully charged. |
Conditions for Setting the DTC
The BCM detects that the ignition 1 signal is shorted to ground, voltage, or open in the current ignition cycle.
Action 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 class 2 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 class 2 serial data communications circuits. |
Conditions for Clearing the DTC
| • | A current DTC clears on the next malfunction free cycle. |
| • | 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, 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.
| ⇒ | If any parameters are incorrect in any key position, refer to the Circuit/System Testing or Component Testing. |
Ignition Switch Position | Starter Switch | Accessory Switch | Ignition Run Start Switch |
|---|---|---|---|
Operating Conditions: Drivers door open to disable RAP | |||
Off | Released | Inactive | Inactive |
Accessory | Released | Active | Inactive |
Run | Released | Active | Active |
Start | Cranking | Inactive | Active |
Circuit/System Testing
- Connect a test lamp between each fuse test terminal of the ignition switch B+ circuit fuse and ground. The test lamp should illuminate.
- Disconnect the harness connector at the ignition switch.
- Connect a test lamp between the ignition switch terminals listed below and ground. The test lamp should illuminate.
- Perform the ignition switch component test. Verify the switch passes the test.
- Disconnect the X1 harness connector at the BCM, test for less than 1.0 volt between the circuit terminals of the BCM listed below and ground:
- Test for less than 1.0 ohm between the BCM and the ignition switch on the circuits listed below:
- If all circuits test normal, replace the BCM.
Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
| ⇒ | 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 4 |
| • | B+ terminal 6 |
| • | Ignition terminal 3 |
| • | Ignition terminal 5 |
| • | Ignition terminal 7 |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for an open/high resistance. |
| • | B+ terminal 4 |
| • | B+ terminal 6 |
Important: The ignition switch component test must be performed before proceeding with this test to verify the integrity of the switch.
| ⇒ | If the ignition switch does not test normal, replace the ignition switch. |
| • | B+ terminal 25 |
| • | Ignition terminal 21 |
| • | Ignition terminal 22 |
| • | Ignition terminal 23 |
| ⇒ | If greater than specified, test the circuit for a short to voltage. |
| • | B+ terminal 25, X1 and 4 |
| • | B+ terminal 25, X1 and 6 |
| • | Ignition terminal 21, X1 and 5 |
| • | Ignition terminal 22, X1 and 7 |
| • | Ignition terminal 23, X1 and 3 |
| ⇒ | If greater than specified, test the circuit for open/high resistance. |
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. |
Ignition Switch Position | Terminals 5 and 6 | Terminals 4 and 6 | Terminals 3 and 4 | Terminals 4 and 7 |
|---|---|---|---|---|
Off | Infinite | Infinite | Infinite | Infinite |
Accessory | Infinite | Infinite | < 5.0 ohms | Infinite |
Run | Infinite | Infinite | < 5.0 ohms | < 5.0 ohms |
Start | < 5.0 ohms | Infinite | Infinite | < 5.0 ohms |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.
| • | Control Module References for module replacement, setup, and programming |
