SAE J1939 fault codes for liquid and gaseous fuel systems. Includes SPN and FMI diagnostic codes for fuel consumption, fuel economy, fuel injection, gaseous fuel pressure, alternate fuel systems, and fuel leakage detection on heavy-duty engines.
Diagnostic Code SPN 231 FMI 8: Meaning and Fix SPN 231 FMI 8 is often encountered in heavy-duty vehicles after ECM replacements or forced DPF regens. This fault indicates abnormal frequency or pulse width in the trip fuel gaseous data stream. Such irregularities can lead to incorrect fuel calculations, impacting performance and emissions. For technicians, … Read more
Diagnostic Code SPN 231 FMI 21: Meaning and Fix SPN 231 FMI 21 indicates that the Trip Fuel (Gaseous) accumulation value reported on the J1939 datalink has drifted abnormally low, falling outside the expected calibrated range. This parameter, superseded by SPN 1039 per SAE J1939-71, tracks cumulative gaseous fuel consumption per trip cycle. Technicians commonly … Read more
Diagnostic Code SPN 231 FMI 20: Meaning and Fix SPN 231 FMI 20 is associated with a data drift high fault in the trip fuel (gaseous) system. This fault typically appears in practice after extensive idling periods when the ECM detects irregular fuel consumption patterns. Technicians often encounter this code following unintended changes in fuel … Read more
Diagnostic Code SPN 231 FMI 19: Meaning and Fix SPN 231 FMI 19 indicates that the Electronic Control Unit (ECM) received network data for trip fuel (gaseous) that was in error, typically due to a corrupted or invalid message from a secondary controller. This code commonly appears after a forced DPF regeneration when a gas … Read more
Diagnostic Code SPN 231 FMI 17: Meaning and Fix SPN 231 FMI 17 indicates that the gaseous trip fuel accumulation value, cross-referenced to SPN 1039, has fallen below the normal operating threshold without reaching a critical failure level. The ECM registers this as a least-severe data validity fault. This code commonly appears on CNG-powered municipal … Read more
Diagnostic Code SPN 231 FMI 16: Meaning and Fix SPN 231 FMI 16 relates to the Trip Fuel (Gaseous) reading being above the normal operating range, moderately severe. Technicians often encounter this fault after ECM replacements or recalibrations. It can signal a discrepancy in fuel consumption data, particularly in systems using gaseous fuels like CNG … Read more
Diagnostic Code SPN 231 FMI 15: Meaning and Fix SPN 231 FMI 15 indicates that the ECM has detected a gaseous fuel trip value above the normal operating range but not yet at a critical failure level. This fault commonly appears after a forced DPF regeneration when fuel pressure spikes temporarily. Technicians frequently encounter this … Read more
Diagnostic Code SPN 231 FMI 10: Meaning and Fix SPN 231 FMI 10 indicates an abnormal rate of change within the gaseous trip fuel measurement signal, flagged when the ECM detects delta values exceeding calibrated thresholds between consecutive data samples. Per SAE J1939-71, this fault is commonly encountered on CNG-powered municipal buses or LNG heavy … Read more
Diagnostic Code SPN 230 FMI 8: Meaning and Fix SPN 230 FMI 8 indicates an abnormal frequency, pulse width, or period detected on the Total Idle Fuel Used (Gaseous) parameter, internally redirected to SPN 1010 per SAE J1939-71 revision. The ECM receives out-of-range timing signals from the gaseous fuel flow metering circuit, corrupting idle fuel … Read more
Diagnostic Code SPN 230 FMI 21: Meaning and Fix SPN 230 FMI 21 indicates that the total idle fuel used (gaseous) signal has drifted below the expected valid range. This code often appears after a forced DPF regeneration or ECM replacement when the fuel rate sensor offset has not been recalibrated. Technicians may notice erratic … Read more