Pinpoint Test I: DTC B2792
Fire Suppression System
Pinpoint Tests
Pinpoint Test I: DTC B2792
Refer to Wiring Diagram Set 96, Police Option for schematic and connector information. Diagrams By Number
Normal Operation
The Fire Suppression System Module (FSSM) monitors all of the firing loop circuits for a cross-link (short together) between the circuits of another firing loop. If the FSSM detects a short between the circuits of a firing loop and another firing loop (cross-link), it stores DTC B2792 in memory and illuminates the Fire Suppression Indicator Lamp (FSIL).
- DTC B2792 (Cross Link Between Firing Loops) - sets when the FSSM detects a short between the circuits of 2 different firing loops (cross-link). This DTC causes the FSIL to illuminate.
This pinpoint test is intended to diagnose the following:
- Short circuit between firing loops
- LH fire suppressor/LH external fire suppressor actuator
- RH fire suppressor/RH external fire suppressor actuator
- FSSM
PINPOINT TEST I: DTC B2792 - CROSS LINK BETWEEN FIRING LOOPS
WARNING: To reduce the risk of accidental deployment, never probe the connectors on the fire suppressors. Failure to follow this instruction may cause unintentional deployment of the suppressors, which may result in serious personal injury.
WARNING: To prevent inadvertent deployment of the fire suppression system (FSS), do not defeat, cut or remove wiring connector shorting bars, including when servicing or removing the system. These wiring connectors incorporate shorting bars to reduce the potential for unintended suppressor activation from static electricity charges. Failure to follow this warning may result in serious personal injury or death.
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
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
NOTE: The fire suppression system must be fully operational and free of faults before releasing the vehicle to the customer.
NOTE: Failure to disconnect the battery when instructed results in false resistance readings. Refer to Battery, Mounting and Cables Battery Disconnect.
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I1 CHECK THE FSSM DTCs FROM THE SELF-TEST
- Check the recorded results from the FSSM self-test.
- Was DTC B2792 retrieved on-demand during the self-test?
Yes
GO to I2.
No
This is an intermittent fault when present as a Continuous Memory Diagnostic Trouble Code (CMDTC) only. GO to I5.
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I2 CHECK THE FSSM FOR A CROSSLINK FAULT BETWEEN THE LH AND RH FIRING LOOP 1 CIRCUITS
- WARNING: To reduce the risk of accidental deployment, do not use any memory saver devices when depowering the fire suppression system. Failure to follow this instruction may result in serious personal injury.
- Depower the fire suppression system. Refer to Fire Suppression System Depowering and Repowering Procedures.
- Disconnect: FSSM C3281A.
- Measure the resistance between the LH and RH loop FSSM pins, component side, as follows:
- Are the resistances greater than 10,000 ohms?
Yes
GO to I3.
No
INSTALL a new FSSM. REFER to Fire Suppression System Module (FSSM) Service and Repair. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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I3 CHECK FOR A CROSSLINK FAULT BETWEEN THE LH AND RH FIRING LOOP 1 CIRCUITS
- Connect: FSSM C3281A.
- Disconnect: LH Fire Suppressor C4317 and RH Fire Suppressor C4316.
- For vehicles equipped with external fire suppressor actuators, refer to Fire Suppressor - With External Fire Suppressor Actuator Fire Suppressor - With External Fire Suppressor Actuator to access the LH fire suppressor C4317.
- Measure the resistance between C4316 and C4317 pins as follows
- Are the resistances greater than 10,000 ohms?
Yes
GO to I4.
No
INSTALL a new wiring harness. CLEAR the DTCs. REPEAT the self-test. GO to I6.
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I4 CHECK FOR CORRECT FSSM OPERATION
- WARNING: To reduce the risk of accidental deployment, do not use any memory saver devices when depowering the fire suppression system. Failure to follow this instruction may result in serious personal injury.
- Depower the fire suppression system. Refer to Fire Suppression System Depowering and Repowering Procedures.
- Disconnect all the FSSM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the FSSM connectors and make sure they seat correctly.
- Connect: All previously disconnected FSSM component(s)/connector(s) and make sure they seat correctly.
- Repower the fire suppression system. Do not prove out the fire suppression system at this time. Refer to Fire Suppression System Depowering and Repowering Procedures.
- Enter the following diagnostic mode on the scan tool: Self-Test - FSSM.
- Was the original DTCs retrieved on-demand during self-test?
Yes
INSTALL a new FSSM. REFER to Fire Suppression System Module (FSSM) Service and Repair. CLEAR the DTCs. REPEAT the self-test. GO to I6.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. GO to I6.
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I5 CHECK FOR AN INTERMITTENT FAULT
- Ignition OFF.
- WARNING: To reduce the risk of accidental deployment, do not use any memory saver devices when depowering the fire suppression system. Failure to follow this instruction may result in serious personal injury.
- Depower the fire suppression system. Refer to Fire Suppression System Depowering and Repowering Procedures.
- Inspect the FSSM and accessible fire suppression system wiring for the following:
- connectors for corrosion, loose or spread terminals and loose or frayed wire connections at terminals.
- wire harnesses for any damage, pinched, cut or pierced wires.
- Connect: All previously disconnected component(s)/connector(s) and make sure they seat correctly.
- Repower the fire suppression system. Do not prove out the fire suppression system at this time. Refer to Fire Suppression System Depowering and Repowering Procedures.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: Self-Test - FSSM.
- Was DTC B2792 retrieved on-demand during self-test?
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 the self-test. GO to I2.
No
The fault is not present and cannot be recreated at this time. CLEAR the DTCs. REPEAT the self-test. GO to I6.
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I6 CHECK FOR ADDITIONAL FIRE SUPPRESSION SYSTEM 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.
- Connect: All previously disconnected FSSM component(s)/connector(s) make sure they seat correctly.
- Repower the fire suppression system. Do not prove out the fire suppression system at this time. Refer to Fire Suppression System Depowering and Repowering Procedures.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: Self-Test - FSSM.
- Are any FSSM DTCs retrieved on-demand during self-test?
Yes
Do not clear any DTCs until all DTCs have been resolved. GO to the DTC Charts for pinpoint test direction. Diagnostic Trouble Code Tests and Associated Procedures
No
CLEAR all FSSM DTCs. PROVE OUT the fire suppression system. The repair is complete. RETURN the vehicle to the customer.
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