GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2008 🢒 LaCrosse 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC 056

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 056: 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, illuminate the passenger air bag status OFF indicator 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 class 2 circuit.
    • The SDM will set DTC B0092.
    • The SDM disables the instrument panel (I/P) module deployment loop.
    • The PPS will illuminate the passenger air bag status OFF indicator.
    • The SDM requests the instrument panel cluster (IPC) to illuminate the AIR BAG indicator.

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 100 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.

Reference Information

Schematic Reference

SIR Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

SIR System Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification
  1. Ignition ON, use the scan tool. Retrieve the DTCs. Refer to Passenger Presence System Flash Code Procedures . Verify DTC 032, DTC 034 or DTC 036 are not set.
    2. ⇒If either DTC 032, DTC 034 or DTC 036 is set, then refer to Diagnostic Trouble Code (DTC) List - Vehicle .
  2. If the PPS has been replaced. Verify the correct PPS has been installed.
    3. ⇒If the incorrect PPS was installed, replace with the correct PPS and perform the Passenger Presence System Rezeroing .
  3. Ignition ON, verify that the rezeoring procedure was performed successfully and that DTC 056 is not set as current. Refer to Passenger Presence System Flash Code Procedures .
    4. ⇒If DTC 0056 is set as current, replace the PPS.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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