DSM.0008 Ver 1.0
FCCC MT-45 / MT 55 CNG Diagnostics Service Manual
February 15, 2022
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FCCC MT CNG
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FCCC MT CNG
DSM.0008 Ver 1.0
FCCC MT-45 / MT 55 CNG Diagnostics Service Manual
February 24, 2022
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Engine Misfire Diagnostics
1. Perform the preliminary vehicle inspection in procedure DSM.0009.
2. Connect the diagnostic scan tool and record all fault code information.
3. Clear all fault code information.
4. If any fault code other than a SPN: 132 FMI: 31 is present, diagnose and repair all prevailing fault codes first.
Circuit / System Verification
SPN: 1322
FMI: 31
FMI 2: Fuel Injector Malfunction
Fault Codes
The following fault code(s) may set when vehicle ignition is left in the ON position while the driver does not engage
the starter within approximately 30 seconds.
SPN
FMI
Type
MIL
Possible Faults
1322
31
B
Yes
• Fuel injector malfunction
A vehicle that runs rough or has a rough idle condition is exhibited when the vehicle will start and run but has an
abnormal vibration. This condition may be accompanied by a diagnostic trouble code (DTC). When diagnosing a
rough idle condition with DTC faults, always follow the diagnostic procedures for any active fault codes before
diagnosing the rough idle.
This symptom-based diagnostic section is designed to assist in diagnosing a general engine misfire. The following
issues are possible causes of a random and/or multiple cylinder misfire.
1. Injector(s) fault.
2. Ignition system fault.
3. Restricted induction or exhaust system.
4. Restricted CNG system component.
5. Mechanical engine failure(s).
6. Engine sensor fault.
7. Abnormal fuel pressure.
Symptom Description
