Pinpoint Test F: LFC 56/DTC B1871
Air Bag and Safety Belt Pretensioner Supplemental Restraint System (SRS)
Pinpoint Tests
Pinpoint Test F: LFC 56/DTC B1871
Refer to Wiring Diagram Set 46, Supplemental Restraint System for schematic and connector information. Diagrams By Number
Normal Operation
The Restraints Control Module (RCM) monitors the status of the Passenger Air Bag Deactivation (PAD) switch at pin C310A pin 23, circuit CR224 (GN). The PAD switch signals the RCM by switching a resistance to ground. If the RCM senses 900-1,100 ohms in the PAD switch, it enables the passenger air bag and turns off the PAD switch warning indicator lamp. If the RCM senses 200-400 ohms in the PAD switch, it deactivates the passenger air bag and turns the PAD switch warning indicator lamp on. If the RCM detects an invalid resistance, open circuit, short to ground or short to voltage, it will store DTC B1871 in memory and send a message to the Instrument Cluster (IC) module to flash Lamp Fault Code (LFC) 56 (or higher priority code if one exists) on the air bag warning indicator.
- DTC B1871 (Passenger Air Bag Disable Module Fault) - If the RCM detects an open circuit, short to ground or short to battery for greater than 2.2 seconds on the PAD switch circuit, it will set this DTC.
This pinpoint test is intended to diagnose the following:
- Damaged wiring, terminals or connectors
- PAD switch
- RCM
PINPOINT TEST F: LFC 56/DTC B1871
NOTICE: Use the correct probe adapter(s) from the Flex Probe Kit when taking measurements. Failure to use the correct probe adapter(s) may damage the connector.
Most faults are due to connector and/or wiring concerns. Carry out a thorough inspection and verification before proceeding with the pinpoint test. Inspection and Verification
NOTE: Supplemental Restraint System (SRS) components should only be disconnected or reconnected when instructed to do so within a pinpoint test step. Failure to follow this instruction may result in incorrect diagnosis of the SRS.
NOTE: The SRS must be fully operational and free of faults before releasing the vehicle to the customer.
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F1 RETRIEVE RCM DTCs
- Enter the following diagnostic mode on the scan tool: Self Test - RCM.
- Was DTC B1871 retrieved on-demand during self-test?
Yes
This fault cannot be cleared until it is corrected and the DTC is no longer retrieved on-demand during self-test. GO to F2.
No
This is an intermittent fault when present as a Continuous Memory Diagnostic Trouble Code (CMDTC) only. GO to F7.
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F2 CHECK THE PAD SWITCH RESISTANCE (PAD_C_RES) PID IN THE ON POSITION
- Place the PAD switch in the ON position.
- Enter the following diagnostic mode on the scan tool: DataLogger - RCM PID.
- Enter the following diagnostic mode on the scan tool: PAD_C_RES PID.
- Is the PID value between 900 and 1,100 ohms?
Yes
GO to F3.
No
GO to F4.
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F3 CHECK THE PAD SWITCH RESISTANCE PID IN THE OFF POSITION
- Place the PAD switch in the OFF position.
- Enter the following diagnostic mode on the scan tool: DataLogger - RCM PID.
- Enter the following diagnostic mode on the scan tool: PAD_C_RES PID.
- Is the PID value between 200 and 400 ohms?
Yes
INSTALL a new RCM. REFER to Restraints Control Module (RCM) Service and Repair. GO to F8.
No
GO to F4.
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F4 CHECK PAD SWITCH CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Depower the SRS. Refer to Supplemental Restraint System (SRS) Depowering and Repowering Supplemental Restraint System (SRS) Depowering and Repowering.
- Disconnect: PAD Switch C2099.
- Disconnect: RCM C310A and C310B.
- Repower the SRS. Do not prove out the SRS at this time. Refer to Supplemental Restraint System (SRS) Depowering and Repowering Supplemental Restraint System (SRS) Depowering and Repowering.
- Ignition ON.
- Measure the voltage between PAD C2099-4, circuit CR224 (GN), harness side and ground.
- Is any voltage present?
Yes
REPAIR circuit CR224 (GN). GO to F8.
No
GO to F5.
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F5 CHECK PAD SWITCH CIRCUIT FOR AN OPEN
- Ignition OFF.
- Depower the SRS. Refer to Supplemental Restraint System (SRS) Depowering and Repowering Supplemental Restraint System (SRS) Depowering and Repowering.
- Measure the resistance between RCM C310a-23, circuit CR224 (GN), harness side and PAD switch C2099-4, circuit CR224 (GN), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to F6.
No
REPAIR circuit CR224 (GN). GO to F8.
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F6 CHECK PAD SWITCH GROUND CIRCUIT FOR AN OPEN
- Measure the resistance between PAD switch C2099-3, circuit GD174 (BK/WH), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
INSTALL a new PAD switch. REFER to Passenger Air Bag Deactivation (PAD) Switch Service and Repair. GO to F8.
No
REPAIR circuit GD174 (BK/WH). GO to F8.
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F7 CHECK FOR AN INTERMITTENT FAULT
- Enter the following diagnostic mode on the scan tool: Self Test - RCM.
- Was DTC B1871 retrieved on-demand during self-test?
Yes
This fault cannot be cleared until it is corrected and the DTC is no longer retrieved on-demand during self-test. GO to F2.
No
CHECK for causes of intermittent faults on circuit CR224 (GN). ATTEMPT to recreate the hard fault by flexing the wire harness and cycling the ignition key frequently. Do not install any new SRS components at this time. SRS components should only be installed when directed to do so in the pinpoint test. REPAIR any intermittent wiring, terminal or connector concerns found. GO to F8.
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F8 CHECK FOR ADDITIONAL SRS DTCs
- Ignition OFF.
- WARNING: Turn the ignition OFF and wait one minute to deplete the backup power supply. Failure to follow this instruction may result in serious personal injury or death in the event of an accidental deployment.
- Reconnect all SRS components (if previously disconnected).
- If previously directed to depower the SRS, repower the SRS. Do notprove out the SRS at this time. Refer to Supplemental Restraint System (SRS) Depowering and Repowering Supplemental Restraint System (SRS) Depowering and Repowering.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: Self Test - RCM.
- Are any RCM DTCs retrieved indicating a fault?
Yes
Do not clear any DTCs until all DTCs have been resolved. GO to the DTC Chart for pinpoint test direction. Diagnostic Trouble Code Tests and Associated Procedures
No
CLEAR all RCM CMDTCs. PROVE OUT the SRS. Repair is complete. RETURN the vehicle to the customer.
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