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 B1385: Device Ignition START CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage |
|---|---|---|---|
12-Volt Reference | B1385 | B1385¹ | -- |
Crank Voltage | B1385 | B1385 | B1385 |
¹ 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 inputs OFF, ignition 3 voltage, crank voltage and ignition 1 voltage 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 Start position, the Crank circuit 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 crank 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 engine will not crank. |
| • | 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 crank circuit. Refer to Testing for Intermittent Conditions and Poor Connections .
Reference Information
Schematic Reference
Connector End View Reference
Master Electrical Component List
Electrical Information Reference
Circuit/System Testing
- Ignition OFF, disconnect the harness connector of the ignition switch.
- Verify that a test lamp illuminates between the 12-volt reference terminal 6 and ground.
- Disconnect harness connector C-1 of the BCM. Connect the harness connector of the ignition switch.
- Test for less then 1 ohm of resistance between the 12 volt reference circuit terminal 25 and crank voltage terminal 21 with the ignition switch in the START position.
- Connect a 3-amp fused jumper between B+ and the 12-volt reference circuit terminal 25 of BCM harness connector C-1.
- With the ignition switch in the OFF, ACCY and RUN positions, test for less than 1 volt between crank voltage circuit terminal 21 of BCM connector C-1 and ground.
- If all circuits test normal, test or replace the BCM.
| ⇒ | If the test lamp does not illuminate, test the 12-volt reference circuit for a short to ground or an open/high resistance, and test the crank voltage circuit for a short to ground. If the circuits test normal, replace the BCM. |
| ⇒ | If greater than 1 ohm, test the crank voltage circuit for open/high resistance. If the circuit tests normal, test or replace the ignition switch. |
| ⇒ | If greater than 1 volt in either position, test the crank voltage circuit for a short to voltage. If the circuit tests normal, test or replace the ignition switch. |
Component Testing
Ignition Switch
Using the Resistance Test below, check the resistance between the pins of the ignition switch listed in each switch position listed.
| ⇒ | If any reading is other than specified, replace the ignition switch. |
Ignition Switch Position | Pins 6 and 3 | Pins 6 and 5 | Pins 6 and 7 | Pins 4 and 3 | Pins 4 and 5 | Pins 4 and 7 |
|---|---|---|---|---|---|---|
Off | Infinite | Infinite | Infinite | Infinite | Infinite | Infinite |
Accessory | Infinite | Infinite | Infinite | < 5.0 ohms | Infinite | Infinite |
Run | Infinite | Infinite | Infinite | < 5.0 ohms | Infinite | < 5.0 ohms |
Start | Infinite | < 5.0 ohms | Infinite | Infinite | Infinite | < 5.0 ohms |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for module replacement, setup, and programming |
