GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2005 🢒 LaCrosse 🢒 Restraints 🢒 SIR 🢒 DTC 056

Circuit 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.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC 056 PPS Internal System Fault

Conditions for Running the DTC

Ignition 1 voltage is within the normal operating voltage range.

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, then communicate with the SDM via non class 2 circuit.
    • The SDM will set DTC B0092.
    • The SDM disables the instrument panel module (IPM) deployment loop.
    • The PPS will turn ON the passenger air bag status OFF indicator.
    • 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.
    • If service kit was installed, you performed the rezeroing procedure with a scan tool.

Diagnostic Aids

Verify that the seat cushion is dry. If seat cushion is wet, allow cushion to dry for 48 hours using a fan. Refer to Front Seat Cushion Cover Replacement .

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.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step is requesting the PPS DTCs, checking to see if DTC 034 or DTC 036 is current.

Step

Action

Yes

No

Schematic Reference: SIR Schematics

Connector End View Reference: SIR Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, request the PPS DTCs. Use the Passenger Presence System Flash Code Procedures to retrieve PPS DTCs.

Does DTC 034 or DTC 036 set as current?

Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 3

3

Was a new passenger presence system (PPS) service kit installed?

Go to Step 4

Go to Step 5

4

When a PPS service kit has been installed you must perform the rezeroing procedure. Refer to Control Module References for replacement, setup, and programming.

Did you complete the rezeroing procedure?

Go to Step 5

--

5
  1. Use the scan tool in order to clear the SIR and PPS DTCs.
  2. Perform the PPS rezeroing procedure. Refer to Control Module References for replacement, setup, and programming.
  3. Cycle the ignition OFF then back ON, with the engine OFF.
  4. Use the Passenger Presence System Flash Code Procedures to retrieve PPS DTCs.

Does DTC 056 reset?

Go to Step 6

Go to Step 7

6
  1. Turn OFF the ignition.

    2. Important: The PPS, heated seat element, and seat bottom cushion is only serviced as a complete kit.

  2. Replace the PPS. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 7

--

7
  1. Reconnect all SIR and PPS system components.
  2. Verify that all components, connectors, and connector position assurances (CPAs) are properly mounted.
  3. Use the scan tool in order to clear the SIR and PPS DTCs.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK