DTC 056

DTC 056

Diagnostic Instructions

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

DTC Descriptor

DTC 056
- PPS Internal System Fault

Circuit/System Description

The inflatable restraint Passenger Presence System (PPS) continuously monitors for critical faults. If the PPS determines there is a fault internal to the electronic control unit (ECU) or sensor mat, the PPS will set DTC 056, turn the passenger air bag status indicator to OFF, and notify the sensing and diagnostic module (SDM) of a fault in the PPS through a non class 2 communications circuit. Other DTCs like DTC 034 or DTC 036 may set along with DTC 056. Diagnose all current DTCs before diagnosing DTC 056. The PPS, heated seat element, and seat bottom cushion is only service as a complete kit, which is a calibrated system and must be replaced as a complete unit. If a service kit was installed, DTC 056 will be set current and the Rezeroing Procedure must be performed before the DTC can be cleared.

Conditions for Running the DTC

Ignition voltage is between 9-16 volts.

Conditions for Setting the DTC

* PPS ECU internal electronic fault
* PPS Sensor mat internal electronic fault
* PPS Service kit was installed

Action Taken When the DTC Sets

* The PPS will set a DTC 056, and then communicate with the SDM via non GMLAN circuit.
* The SDM will set DTC B0081.
* 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 via GMLAN serial data.

Conditions for Clearing the DTC

* The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.
* A history DTC will clear once 255 malfunction-free ignition cycles have occurred.

Diagnostic Aids

DTC 034 or DTC 036 may set along with DTC 056. Diagnose all current DTCs before diagnosing DTC 056. This DTC 056 indicates that you have installed a service kit or have an internal fault to the ECU or sensor mat.

Circuit/System Testing

1. Ignition ON, use the scan tool. Go to the PPS menu, then retrieve the DTCs. Refer to Passenger Presence System Flash Code Procedures. Verify DTC 034 or DTC 036 does not set. Component Tests and General Diagnostics

• If either DTC 034 or DTC 036 sets then refer to Diagnostic Trouble Code (DTC) List - Vehicle. Diagnostic Trouble Code Descriptions

2. Check to see if the PPS has been replaced. Verify the correct PPS has been installed.

• If the incorrect PPS was installed replace with the correct PPS. Then perform the Passenger Presence System Rezeroing. Programming and Relearning

3. Perform the Passenger Presence System Rezeroing and recheck for DTC 056. Verify that DTC 056 does not reset. Programming and Relearning

• If DTC 056 sets, then replace the PPS and rezero.

Repair Instructions

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

* SIR/SRS Wiring Repairs
* Control Module References for SDM and PPS replacement, setup, and programming