B1370

DTC B1370

Circuit Description

The body control module (BCM), monitors the ignition inputs OFF, ignition 3, crank and ignition 1 supplied 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. A 12-volt reference voltage 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.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B1370 Device Ignition 1 (ON and START) Circuit

Conditions for Running the DTC

* The BCM must be powered and must detect a change in the ignition switch circuit states.
* The vehicle 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 for more than 10 seconds 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.

Diagnostic Aids

A history DTC maybe caused by an intermittent short or open in the ignition 1 circuit. refer to Testing for Intermittent Conditions and Poor Connections. Component Tests and General Diagnostics

Test Description

Step 1 - Step 8:

Step 9:

The numbers below refer to the step numbers on the diagnostic table.
3. This step tests the ignition switch for a short circuit between the 12-volt reference supply circuit and the ignition 1 circuit in the OFF position.
4. This step tests the wiring of the ignition 1 circuit for a short to ground or voltage.
5. This step tests the ignition switch for a closed circuit between the ignition switch 12-volt reference supply circuit and the ignition 1 circuit in the Run and Crank switch positions. Care must be taken as the engine may crank during this test.