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Home >> Mercury >> 2011 >> Grand Marquis V8-4.6L >> Repair and Diagnosis >> Restraints and Safety Systems >> Air Bag Systems >> Testing and Inspection >> Pinpoint Tests >> Pinpoint Test V: DTC B2792

Pinpoint Test V: DTC B2792




Air Bag and Safety Belt Pretensioner Supplemental Restraint System (SRS)

Pinpoint Tests

Pinpoint Test V: DTC B2792

Refer to Wiring Diagram Set 46, Supplemental Restraint System for schematic and connector information. Diagrams By Number

Lamp Fault Codes (LFCs)

The following Lamp Fault Code (LFC) indicates the specific fault associated with DTC B2792:

- LFC 12-11 - Cross Link Between Firing Loops

Normal Operation

The Restraints Control Module (RCM) monitors all deployable devices for a cross link fault between circuits. If the RCM detects a short between any of the deployable circuits, it will store a diagnostic trouble code B2792 in memory, flash LFC 12-11 on the air bag warning indicator.





a Fault PIDs that end in OD indicate an on-demand status and are associated with on-demand DTC B2792. Fault PIDs that end in CM indicate continuous memory status and are associated with continuous DTC B2792.

This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- RCM

PINPOINT TEST V: B2792

WARNING: Remove restraint system diagnostic tools from the vehicle prior to road testing. If tools are not removed, the supplemental restraint system (SRS) device may not deploy in a crash. Failure to follow this instruction may result in serious personal injury or death in a crash and possibly violate vehicle safety standards.

WARNING: Never probe the electrical connectors on air bag, Safety Canopy(R) or side air curtain modules. Failure to follow this instruction may result in the accidental deployment of these modules, which increases the risk of serious personal injury or death.

WARNING: Never disassemble or tamper with safety belt buckle/retractor pretensioners or adaptive load limiting retractors or probe the electrical connectors. Failure to follow this instruction may result in the accidental deployment of the safety belt pretensioners or adaptive load limiting retractors which increases the risk of serious personal injury or death.

NOTICE: Use the correct probe adapter(s) when taking measurements. Failure to use the correct probe adapter(s) may damage the connector.

NOTE: The Supplemental Restraint System (SRS) must be fully operational and free of faults before releasing the vehicle to the customer.

NOTE: 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: 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

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V1 RETRIEVE RCM DTCs


- Enter the following diagnostic mode on the scan tool: Self Test - RCM.
- Enter the following diagnostic mode on the scan tool: Datalogger - RCM - View and Record All 2792 Fault PIDs.
- Do any 2792 fault PIDs indicate a fault?

Yes
This fault cannot be cleared until it is corrected and the fault PID is no longer retrieved on-demand during self test. GO to V2.

No
This is an intermittent fault when present as a CMDTC only. GO to V5.

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V2 CHECK DEPLOYABLE CIRCUITS FOR A CROSS LINK FAULT


- Ignition OFF.
- Depower the SRS. Refer to Supplemental Restraint System (SRS) Depowering and Repowering Supplemental Restraint System (SRS) Depowering and Repowering.
- Disconnect: RCM C310a and C310b.
- Disconnect ALL of the affected SRS devices.
- NOTE: Most cross link faults are due to connector and/or wiring harness damage. Carry out a thorough inspection of connector(s) and/or wiring harness for damage.
- Using the following table, measure resistance between the circuits of the affected SRS devices.

Cross Link Fault Chart





- Are the resistances greater than 10,000 ohms between the affected circuits?

Yes
GO to V3.

No
REPAIR the affected circuits. GO to V5.

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V3 CONFIRM THE RCM FAULT


- Connect: RCM C310a and C310b.
- Connect: All Previously Disconnected SRS Components.
-
- 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.
- Enter the following diagnostic mode on the scan tool: Self Test - RCM.
- Enter the following diagnostic mode on the scan tool: DataLogger - RCM - View and Record All 2792 Fault PIDs.
- Refer to PID list in Normal Operation to view 2792 fault PIDs.
- Does the original on-demand 2792 fault PID indicate a fault?

Yes
INSTALL a new RCM. REFER to Restraints Control Module (RCM) Service and Repair. GO to V5.

No
CHECK for causes of the intermittent fault. 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, terminals or connector concerns found. GO to V4.

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V4 CHECK FOR AN INTERMITTENT FAULT


- Ignition OFF.
- Depower the SRS. Refer to Supplemental Restraint System (SRS) Depowering and Repowering Supplemental Restraint System (SRS) Depowering and Repowering.
- If a cross link fault is with the driver air bag module loop 1 or loop 2:
- Remove the driver air bag module. Refer to Driver Air Bag Module Driver Air Bag Module.
- Connect Restraint System Diagnostic Tool 418-F395 (2 required) to the driver air bag module loop connectors.
- If a cross link fault is with the passenger air bag module loop 1 or loop 2:
- Disconnect the passenger air bag module C256.
- Connect Restraint System Diagnostic Tool 418-F403 to the passenger air bag module C256.
- If a cross link fault is with the driver seat side air bag module:
- Disconnect the driver seat side air bag module C315.
- Connect Restraint System Diagnostic Tool 418-133 to the driver seat side air bag module C315.
- If a cross link fault is with the passenger seat side air bag module air bag module:
- Disconnect the passenger seat side air bag module C316.
- Connect Restraint System Diagnostic Tool 418-133 to the passenger seat side air bag module C316.
- If a cross link fault is with the driver safety belt retractor pretensioner C3014:
- Disconnect the driver safety belt retractor pretensioner C3014.
- Connect Restraint System Diagnostic Tool 418-F088 (105-R0012 or 105-R0013) to the driver safety belt retractor pretensioner C3014.
- If a cross link fault is with the passenger safety belt retractor pretensioner C303:
- Disconnect the passenger safety belt retractor pretensioner C303.
- Connect Restraint System Diagnostic Tool 418-F088 (105-R0012 or 105-R0013) to the passenger safety belt retractor pretensioner C303.
- 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.
- Enter the following diagnostic mode on the scan tool: Self Test - RCM.
- Enter the following diagnostic mode on the scan tool: DataLogger - RCM - View and Record All 2792 Fault PIDs.
- Refer to PID list in Normal Operation to view 2792 fault PIDs.
- Do any 2792 fault PIDs indicate a fault?

Yes
The fault condition is now present. This fault cannot be cleared until it is corrected and the DTC is no longer retrieved on-demand during self test.

Using the fault PIDs recorded, GO to V2.

No
CHECK for causes of the intermittent fault. 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, terminals or connector concerns found. GO to V5.

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V5 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 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.
- Enter the following diagnostic mode on the scan tool: Self Test - RCM.
- Are any DTCs retrieved on-demand during self-test?

Yes
Do not clear any DTCs until all DTCs have been resolved. GO to the Supplemental Restraint System (SRS) DTC Chart for pinpoint test direction. Supplemental Restraint System (SRS) DTC Chart

No
CLEAR all CMDTCs. PROVE OUT the SRS. REPAIR is complete. RETURN the vehicle to the customer.

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