DTC U1241 Lost Communication With Scan Tool

Circuit Description

The passenger presence system (PPS) monitors itself for faults and will set/flash DTCs if a fault is detected. The PPS communicates with the inflatable restraint sensing and diagnostic module (SDM) via non class 2 communications. When the SDM receives input from the PPS that a PPS fault has occurred, the SDM will request the instrument panel cluster (IPC) to turn ON the AIR BAG indicator located on the IPC. To determine what DTCs have been set by the PPS, the Tech 2 is used to command the SDM to request the PPS to flash the DTCs using the PASSENGER AIR BAG ON/OFF indicators located on the instrument panel. The Tech 2 sends a string of commands to the SDM that allows the SDM to communicate with the PPS module and initiate the flashing of the DTCs. When the Tech 2 has completed sending the commands, the PPS will begin flashing any current or history DTCs that the system has stored. When the SDM no longer receives commands from the Tech 2, the SDM mistakes this as a communication fault and sets DTC U1241. DTC U1241 will set when the Tech 2 is used to flash DTCs from the PPS or after the PPS has been rezeroed. DTC U1241 does not indicate a system malfunction and will not cause any warning indicators to illuminate. When DTC U1241 sets, cycle the ignition and use the scan tool to clear the code, no further diagnosis is necessary. For more detailed information concerning the PPS, refer to SIR System Description and Operation. For more detailed information concerning PPS flash code and rezeroing procedures, refer to Passenger Presence System Flash Code Procedures and Passenger Presence System Programming and Setup.

Conditions for Running the DTC

Ignition 1 voltage is within the normal operating voltage range.

Conditions for Setting the DTC

DTC U1241 will set when the Tech 2 is used to flash DTCs from the PPS or after the PPS has been rezeroed.

Conditions for Clearing the DTC

A scan tool CLEAR DTC command is issued.

Diagnostic Aids

DTC U1241 does not indicate a system malfunction and will not cause any warning indicators to illuminate. When DTC U1241 sets, cycle the ignition and use the scan tool to clear the code, no further diagnosis is necessary.

Reference Information

Electrical Information Reference • Circuit Testing

• Connector Repairs

• Testing for Intermittent Conditions and Poor Connections

• Wiring Repairs

SYMPTOMS - SIR

IMPORTANT: The following steps must be completed before using the Symptom Tables.

1. Perform the Diagnostic System Check - Vehicle, before using the Symptom Tables in order to verify that all of the following are true:

• There are no DTCs set.

• The control module(s) can communicate via the serial data link.

2. Review the system operation in order to familiarize yourself with the system functions. Refer to SIR System Description and Operation.

Visual/Physical Inspection

• Inspect for aftermarket devices which could affect the operation of the SIR system. Refer to Checking Aftermarket Accessories.

• Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to

Testing for Intermittent Conditions and Poor Connections.

Symptom List

Refer to Air Bag Indicator Circuit Malfunction in order to diagnose the symptom.

Refer to Passenger Presence System Indicator Circuit Malfunction in order to diagnose the symptom.

AIR BAG INDICATOR CIRCUIT MALFUNCTION 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.

Circuit Description

When the ignition is turned ON, the instrument panel cluster (IPC) flashes the AIR BAG indicator seven times. The inflatable restraint sensing and diagnostic module (SDM) performs tests to diagnose critical malfunctions within the SIR system. If no SIR system malfunctions exists, the SDM will request the IPC to turn the AIR BAG indicator OFF after it has flashed 7 times. The AIR BAG indicator is controlled by the SDM via class 2 serial data.

Diagnostic Aids

• If ignition 1 voltage for the SDM is outside of the normal operating voltage range (9-16 volts), the AIR BAG indicator will come ON solid with no DTC set.

• The loss of serial data communication between the SDM and the IPC will cause the AIR BAG indicator to come ON solid. Refer to DTC U1001-U1254 .

Reference Information Schematic Reference

SIR Schematics

Connector End View Reference

SIR Connector End Views

Electrical Information Reference

• Circuit Testing

• Connector Repairs

• Testing for Intermittent Conditions and Poor Connections

• Wiring Repairs

Circuit/System Testing

1. With the ignition ON, with a scan tool, request the ignition voltage parameter in the SIR data list. If the parameter does not read 9-16 volts, test the ignition 1 voltage for a short to voltage, open/high resistance or a short to ground.

о If a condition exists, make the appropriate repair.

2. With the ignition OFF, test the SDM ground circuit for an open or high resistance.

о If a condition exists, make the appropriate repair

3. Remove the inflatable restraint SDM connector. Inspect the SDM connector for damage or corrosion that may cause a malfunction.

о If damage or corrosion is found make the appropriate repair.

4. Replace the SDM.

5. If replacement of the SDM does not repair the vehicle, replace the IPC.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• SIR/SRS Wiring Repairs

• Control Module References for SDM and IPC replacement, setup and programming

PASSENGER PRESENCE SYSTEM INDICATOR CIRCUIT MALFUNCTION 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.

Circuit Description

The PASSENGER AIR BAG ON/OFF indicators located on the instrument panel are used to notify the driver when the passenger presence system (PPS) has enabled or disabled the instrument panel (I/P) inflator module. The PPS air bag indicators will also inform the driver of

any PPS malfunctions. When the ignition is turned on, the PPS module is supplied with ignition 1 voltage and commands both PASSENGER AIR BAG ON/OFF indicators ON for 5 seconds. The PPS module conducts tests on the PPS components and circuits while both PASSENGER AIR BAG ON/OFF indicators are ON. If no malfunctions are detected the PPS module will turn the PASSENGER AIR BAG indicator ON or OFF depending on the status of the PPS. If a malfunction is detected, the PPS module will store a DTC, default the PPS to the OFF state and communicate with the SDM that a DTC has been set. The SDM will request the instrument panel cluster (IPC) to turn the AIR BAG indicator ON to notify the driver of a PPS malfunction.

Diagnostic Aids

Use this procedure to diagnosis one or both PPS indicators inoperative.

The following can cause an intermittent condition:

• A short in the passenger air bag OFF indicator control circuit

• A short in the passenger air bag ON indicator control circuit

• An open or high resistance in the passenger air bag OFF indicator control circuit

• An open or high resistance in the passenger air bag ON indicator control circuit

Reference Information SIR Schematics

SIR Schematics

Connector End View Reference

• SIR Connector End Views

• Antilock Brake System Connector End Views

Electrical Information Reference

• Circuit Testing

• Connector Repairs

• Testing for Intermittent Conditions and Poor Connections

• Wiring Repairs

Circuit/System Testing

1. With the ignition OFF, Disconnect the inside accessory switch connector. Inspect the

connector for damage or corrosion that may cause a malfunction о If a condition exists, make the appropriate repair.

2. Ignition ON, test the ignition 1 voltage circuit for 9-16 volts. If ignition 1 voltage is not present, test for an open/high resistance or a short to ground.

о If a condition exists, make the appropriate repair.

3. With the ignition OFF, Connect a test lamp between the ignition 1 voltage circuit and the passenger air bag OFF indicator control circuit at the accessory switch connector terminals. Ignition ON, test lamp should illuminate.

о If the test lamp illuminates, replace the accessory switch.

4. Test the passenger air bag OFF indicator control circuits for a short to ground, open/high resistance.

о If a condition exists, make the appropriate repair

5. Replace the PPS.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• Accessory Switch Replacement

• SIR/SRS Wiring Repairs

• Control Module References for PPS replacement, setup and programming SIR DISABLING AND ENABLING

SIR component location affects how a vehicle should be serviced. There are parts of the SIR system installed in various locations around a vehicle. To find the location of the SIR components refer to SIR Identification Views.

There are several reasons for disabling the SIR system, such as repairs to the SIR system or servicing a component near or attached to an SIR component. There are several ways to disable the SIR system depending on what type of service is being performed. The following information covers the proper procedures for disabling/enabling the SIR system.

SIR Disabling and Enabling

Condition

Action

If the vehicle was involved in an accident with an air bag deployment.

Disconnect the negative battery cable(s) *. Refer to Repairs and Inspections Required

After a Collision.

When performing SIR diagnostics.

Follow the appropriate SIR service manual diagnostic procedure(s) *

When removing or replacing an SIR component or a component attached to an SIR component.

Disconnect the negative battery cable(s) *

If the vehicle is suspected of having shorted electrical wires.

Disconnect the negative battery cable(s) *

When performing electrical diagnosis on components other than the SIR system.

Remove the SIR/Airbag fuse(s) when indicated by the diagnostic procedure to disable the SIR system

* DTCs will be lost when the negative battery cable is disconnected.

SIR Service Precautions

CAUTION: When performing service on or near the SIR components or the SIR wiring, the SIR system must be disabled. Failure to observe the correct procedure could cause deployment of the SIR components. Serious injury can occur. Failure to observe the correct procedure could also result in unnecessary SIR system repairs.

The inflatable restraint sensing and diagnostic module (SDM) maintains a reserved energy supply. The reserved energy supply provides deployment power for the air bags if the SDM loses battery power during a collision. Deployment power is available for as much as 1 minute after disconnecting the vehicle power. Waiting 1 minute before working on the system after disabling the SIR system prevents deployment of the air bags from the reserved energy supply.

General Service Instructions

The following are general service instructions which must be followed in order to properly repair the vehicle and return it to its original integrity:

• Do not expose inflator modules to temperatures above 65°C (150°F).

• Verify the correct replacement part number. Do not substitute a component from a different vehicle.

• Use only original GM replacement parts available from your authorized GM dealer. Do not use salvaged parts for repairs to the SIR system.

Discard any of the following components if it has been dropped from a height of 91 cm (3 feet) or greater:

• Inflatable restraint sensing and diagnostic module (SDM)

• Any Inflatable restraint air bag module

• Inflatable restraint steering wheel module coil

• Any Inflatable restraint sensor

• Inflatable restraint seat belt pretensioners

• Inflatable restraint Passenger Presence System (PPS) module or sensor

Disabling Procedure - Air Bag Fuse

1. Turn the steering wheel so that the vehicles wheels are pointing straight ahead.

2. Place the ignition in the OFF position.

IMPORTANT: The SDM may have more than one fused power input. To

ensure there is no unwanted SIR deployment, personal injury or unnecessary SIR system repairs, remove all fuses supplying power to the SDM. With all SDM fuses removed and the ignition switch in the ON position, the AIR BAG warning indicator illuminates. This is normal operation and does not indicate a SIR system malfunction.

3. Locate and remove the fuse(s) supplying power to the SDM. Refer to SIR Schematics or Electrical Center Identification Views.

4. Wait 1 minute before working on the system.

Enabling Procedure - Air Bag Fuse

1. Place the ignition in the OFF position.

2. Install the fuse(s) supplying power to the SDM. Refer to SIR Schematics or Electrical Center Identification Views.

3. Turn the ignition switch to the ON position. The AIR BAG indicator will flash then turn OFF.

4. Perform the Diagnostic System Check - Vehicle if the AIR BAG warning indicator does not operate as described. Refer to Diagnostic System Check - Vehicle.

Disabling Procedure - Negative Battery Cable

1. Turn the steering wheel so that the vehicles wheels are pointing straight ahead.

2. Place the ignition in the OFF position.

3. Disconnect the negative battery cable from the battery. Refer to Battery Negative Cable Disconnection and Connection.

4. Wait 1 minute before working on system

Enabling Procedure - Negative Battery Cable

1. Place the ignition in the OFF position.

2. Connect the negative battery cable to the battery. Refer to Battery Negative Cable Disconnection and Connection.

3. Turn the ignition switch to the ON position. The AIR BAG indicator will flash then turn OFF.

4. Perform the Diagnostic System Check - Vehicle if the AIR BAG warning indicator does not operate as described. Refer to Diagnostic System Check - Vehicle.

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