B0042

DTC B0042

CIRCUIT DESCRIPTION
The following diagnostics are designed to diagnose circuit failures for both single stage and dual stage air bag systems. The light duty G/H models are equipped with dual stage air bags and the heavy duty G/H models are equipped with single stage air bags. The inflatable restraint steering wheel module deployment loop consists of a steering wheel module, steering wheel module coil, steering wheel module high control, and steering wheel module low control circuits. There are shorting bars used within the steering wheel module coil connector which will short together the steering wheel module high and steering wheel module low control circuits when the connector is disconnected. This will help to prevent unwanted deployment of the inflator module during servicing. When the ignition is turned ON, the inflatable restraint sensing and diagnostic module (SDM) performs continuous diagnostic tests on the deployment loops to check for proper circuit continuity and for shorts to ground or voltage. If a malfunction is detected, a diagnostic trouble code (DTC) will be stored in memory.

CONDITIONS FOR RUNNING THE DTC
Ignition 1 voltage is within the normal operating voltage range.

CONDITIONS FOR SETTING THE DTC
- DTC B0022-stage 1 or B0042-stage 2 will set when the steering wheel module deployment loop resistance is less than 1.3 ohms for 500 milliseconds.
- DTC B0024-stage 1 or B0043-stage 2 will set when one of the following conditions occur:
- The SDM detects the voltage at steering wheel module high control is shorted to ground or voltage for 500 milliseconds.
- The SDM detects the voltage at steering wheel module high control is less than 2.4 volts and steering wheel module deployment loop resistance is less than 6 ohms for 500 milliseconds.
- DTC B0026-stage 1 or B0044-stage 2 will set when one of the following conditions occurs:
- The SDM detects the steering wheel module deployment loop resistance is greater than 4.8 ohms for 500 milliseconds.
- The SDM detects the voltage at steering wheel module high control is less than 2.4 volts and steering wheel module deployment loop resistance is 6 ohms or greater for 500 milliseconds.

ACTION TAKEN WHEN THE DTC SETS
The SDM commands the AIR BAG indicator ON via Class 2 serial data.

CONDITIONS FOR CLEARING THE DTC
- The condition responsible for setting the DTC no longer exists.
- You issue a scan tool CLEAR DTCs command.
- A history DTC will clear once 255 malfunction free ignition cycles have occurred.

DIAGNOSTIC AIDS
The following can cause an intermittent condition:
- A short between the steering wheel module high and low control circuits
- An open or a high resistance in the steering wheel module high or low control circuits
- A malfunctioning shorting bar on the steering wheel module coil connector

TEST DESCRIPTION

Steps 1-3:

Steps 4-5:

Steps 6-8:

Steps 9-11:

The numbers below refer to the step numbers on the diagnostic table.
2. Inspects the steering wheel module coil in-line connector.
5. Tests for a malfunctioning steering wheel module or steering wheel module coil.
7. Tests for current DTCs. If DTC B0022 or B0042 is present, test for a short between the steering wheel module high and steering wheel module low control circuits for stage 1 or stage 2. If DTC B0024 or B0043 is present, test for a short to ground or voltage in the steering wheel module high and steering wheel module low control circuits for stage 1 or stage 2. If DTC B0026 or B0044 is present, test for an open or high resistance in the steering wheel module high and steering wheel module low control circuits for stage 1 or stage 2.