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 continuous memory and illuminates the fire suppression system indicator.
- 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 fire suppression system indicator to illuminate.
This pinpoint test is intended to diagnose the following:
- Short circuit between firing loops
- LH fire suppressor
- RH fire suppressor
- 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 the risk of inadvertent deployment of the fire suppression system (FSS), never defeat wiring connector shorting bars or remove the connectors. All fire suppressor wiring connectors incorporate shorting bars to reduce the potential of static electricity charges causing unintended suppressor activation. 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 will result in false resistance readings. Refer to Battery.
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I1 CHECK FOR ON-DEMAND OR CONTINUOUS MEMORY DTCs
- Carry out the FSSM self-test.
- Was DTC B2792 retrieved as an on-demand DTC during the self-test?
Yes
GO to I2.
No
CHECK for causes of the intermittent fault. ATTEMPT to recreate the hard fault by flexing the wire harness and cycling the key in the ignition lock cylinder frequently. REPEAT the self-test.
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I2 CHECK THE FSSM FOR CROSSLINK BETWEEN #1 FIRING LOOPS
- 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.
- Disconnect: Negative Battery Cable.
- Wait approximately 60 seconds to allow the fire suppression system backup power supply to deplete.
- Disconnect: FSSM C3281a.
- Measure the resistance between the LH loop and the RH loop FSSM pins, component side, as follows:
- Are the resistances greater than 10,000 ohms?
Yes
GO to I3.
No
GO to I7.
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I3 CHECK THE BODY HARNESS CIRCUITS FOR CROSSLINK
- Connect: FSSM C3281a.
- Disconnect: Inline C339.
- Measure the resistance between the inline C339 pins (LH loop and the RH loop), body harness side as follows:
- Are the resistances greater than 10,000 ohms?
Yes
GO to I4.
No
REPAIR the circuit(s) in question. CONNECT the inline C339. CONNECT the negative battery cable. GO to I6.
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I4 CHECK THE LH FIRE SUPPRESSORS
- Connect: Inline C339.
- Disconnect: LH Fire Suppressor C4317.
- Connect: Negative Battery Cable.
- NOTE: DTCs B299A and B299F are expected to be retrieved when the self-test is carried out with the LH fire suppressor C4317 disconnected. These DTCs can be cleared once all the fire suppression connections are restored. If DTC B299A or DTC B299F is retrieved with all the fire suppression connections restored, refer to DTC Charts. Diagnostic Trouble Code Tests and Associated Procedures
- Carry out the FSSM self-test.
- Was DTC B2792 retrieved as an on-demand DTC during the self-test?
Yes
DISCONNECT the negative battery cable. CONNECT the LH fire suppressor C4317. GO to I5.
No
INSTALL a new LH fire suppressor. REFER to Fire Suppressor Removal and Replacement. GO to I6.
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I5 CHECK THE RH FIRE SUPPRESSORS
- Disconnect: RH Fire Suppressor C4317.
- Connect: Negative Battery Cable.
- NOTE: DTCs B29A9 and B29A4 are expected to be retrieved when the self-test is carried out with the RH fire suppressor C4316 disconnected. These DTCs can be cleared once all the fire suppression connections are restored. If DTC B29A9 or DTC B29A4 is retrieved with all the fire suppression connections restored, refer to DTC Charts. Diagnostic Trouble Code Tests and Associated Procedures
- Carry out the FSSM self-test.
- Was DTC B2792 retrieved as an on-demand DTC during the self-test?
Yes
INSTALL a new fire suppression system harness. GO to I6.
No
INSTALL a new RH fire suppressor. REFER to Fire Suppressor Removal and Replacement. GO to I6.
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I6 CHECK FOR ADDITIONAL DTCs
- Refer to the continuous memory DTCs recorded during Step I1.
- Were any continuous memory DTCs retrieved during Step I1?
Yes
REFER to DTC Charts. Diagnostic Trouble Code Tests and Associated Procedures
No
CLEAR the DTCs. REPEAT the self-test.
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I7 CHECK FOR CORRECT FSSM OPERATION
- Disconnect all the FSSM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the FSSM connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new FSSM. REFER to Fire Suppression System Module (FSSM) Service and Repair. REPEAT the self-test.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
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