B0074

DTC B0074

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using the diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC B0074 03
- Passenger Occupant Classification Sensor Circuit Voltage Below Threshold

DTC B0074 07
- Passenger Occupant Classification Circuit Voltage Above Threshold

DTC B0074 08
- Passenger Occupant Classification Circuit Signal Invalid

Diagnostic Fault Information






Circuit/System Description

The passenger presence system (PPS) uses a silicone filled sensor pad located underneath the passenger seat foam cushion and is connected by a hose clamp to a pressure sensor. The weight of the occupant sitting in the front passenger seat is measured as a pressure change within the bladder by the pressure sensor. The pressure sensor is a 3-wire sensor consisting of a power, ground, and signal circuit. The PPS continually monitors itself and if a fault in this circuit occurs, a DTC will set. When the sensing and diagnostic module (SDM) detects this DTC within the PPS, it will notify the customer of the enable/disable status by turning ON the OFF indicator on the PASSENGER AIR BAG ON/OFF indicators. Then the PPS will communicate to the SDM through serial data communications that a PPS fault is present. The SDM will then suppress the deployment of the instrument panel (I/P) module and then turn the AIR BAG indicator ON.

Conditions for Running the DTC

Ignition voltage is between 9-16 volts.

Conditions for Setting the DTC

* The PPS detects the voltage at the PPS sensor signal is less than 0.5 volt or greater than 4.5 volts for 500 milliseconds.
* The PPS detects the voltage at the PPS sensor 5 volt reference is less than 4.5 volts or greater than 9.1 volts for 500 milliseconds.
* The PPS detects the amperage at the PPS sensor low reference is 25 mA or greater for 500 milliseconds.

Action Taken When the DTC Sets

* The PPS will set a DTC, and then communicate with the SDM.
* The SDM disables the I/P module deployment loop.
* The PPS will turn on the passenger air bag status OFF indicator.
* The SDM commands the AIR BAG indicator ON.

Conditions for Clearing the DTC

* The condition for setting the DTC no longer exists.
* A history DTC will clear once 100 malfunction-free ignition cycles have occurred.

Circuit/System Testing

Important:
* The PPS pressure sensor is not serviced separately. The PPS replacement with the PPS pressure sensor must be serviced as a complete unit.

* When removing connectors, inspect for damage or corrosion. Damage or corrosion in the following requires repair or replacement of the affected component/connector:

- The PPS pressure sensor

- The PPS module

- The PPS pressure sensor wiring harness connector

- The PPS module wiring harness connector

Ignition OFF, disconnect the harness connector at the PPS pressure sensor and inspect the component and harness sides for damage or corrosion.

• If damage or corrosion is found, repair or replace as necessary.

1. Ignition ON, test for 4.5-5.5 volts between the voltage reference circuit terminal A and ground.

• If less that the specified range, test the voltage reference circuit for open/high resistance or a short to ground. If the circuit tests normal, replace the PPS.

• If greater that the specified range, test the voltage reference circuit for a short to voltage. If the circuit tests normal, replace the PPS.

Important: The AIR BAG BATT Fuse that supplies B+ voltage must be removed to ensure the PPS module is inactive. An active PPS module may cause inaccurate resistance readings.

2. Ignition OFF, remove the AIR BAG BATT Fuse. Test for less than 2.0 ohms between low reference terminal C and ground.

• If greater than the specified range, test the low reference circuit for open/high resistance. If the circuit tests normal, replace the PPS.

3. Ignition OFF, disconnect the harness connector at the PPS module.
4. Test for infinite resistance between the signal circuit terminal B and ground.

• If less than the specified value, test the signal circuit for a short to ground.

5. Ignition ON, test for less than 1 volt between the signal circuit terminal B and ground.

• If greater than the specified range, test the signal circuit for a short to voltage.

6. Test for less than 1 ohm in the signal circuit between PPS module terminal 6 and PPS sensor terminal B.

• If greater than the specified range, test the signal circuit for open/high resistance. If the circuit tests normal, replace the PPS.

7. If all circuits test normal, replace the PPS which includes the pressure sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* SIR/SRS Wiring Repairs