Caterpillar Fault Codes
Caterpillar built on-highway diesel engines for Class 7 and 8 trucks from the late 1980s through 2009, when CAT exited the on-highway market. The C7, C9, C13, and C15 still power millions of trucks in the wild. ACERT-series engines (2004-2009) are notorious for EGR cooler failures and complex fault diagnostics, and CAT-specific faults are reported as CID/FMI pairs through CAT ET (Electronic Technician) software.
136 fault codes documented· 5 engine variants · CID / FMI codes (CAT ET) · 1999 - 2009 (on-highway)
Most Common Caterpillar Fault Codes
Showing 24 of 136 Caterpillar codes, sorted by severity. Each links to causes, diagnostics, common fixes, and repair cost estimates.
CAT-CID100-FMI3 critical
Engine Oil Pressure Sensor - Voltage Above Normal (Open/Short to High)
CAT-CID100-FMI4 critical
Engine Oil Pressure Sensor - Voltage Below Normal (Short to Low)
CAT-SPN100-FMI1 critical
Engine Oil Pressure Low
CAT-SPN110-FMI0 critical
Engine Coolant Temperature Above Normal
CAT-SPN111-FMI1 critical
Coolant Level Low
CAT-CID100-FMI1 serious
Engine Oil Pressure Sensor - Data Valid But Below Normal Operating Range
CAT-CID1079-FMI7 serious
EGR Valve Actuator - Mechanical System Not Responding
CAT-CID164-FMI0 serious
Injection Actuation Pressure Above Normal
CAT-CID164-FMI1 serious
Injection Actuation Pressure Below Normal
CAT-CID164-FMI3 serious
Injection Actuation Pressure Sensor - Voltage High
CAT-CID164-FMI4 serious
Injection Actuation Pressure Sensor - Voltage Low
CAT-CID165-FMI3 serious
Injection Actuation Pressure Regulator (IAPR) - Open/High
CAT-CID165-FMI4 serious
Injection Actuation Pressure Regulator (IAPR) - Short
CAT-CID165-FMI6 serious
IAPR Current Above Normal
CAT-CID1796-FMI7 serious
Fuel Pressure Regulator - Mechanical
CAT-CID1797-FMI0 serious
Fuel Rail Pressure Above Normal
CAT-CID1797-FMI1 serious
Fuel Rail Pressure Below Normal
CAT-CID1797-FMI3 serious
Fuel Rail Pressure Sensor - Voltage High
CAT-CID1797-FMI4 serious
Fuel Rail Pressure Sensor - Voltage Low
CAT-CID1835-FMI0 serious
DPF Soot Load Above Normal
CAT-CID190-FMI0 serious
Engine Speed / Crankshaft Sensor - Data Valid But Above Normal Operating Range
CAT-CID190-FMI2 serious
Engine Speed / Crankshaft Sensor - Data Erratic, Intermittent, or Incorrect
CAT-CID190-FMI3 serious
Engine Speed / Crankshaft Sensor - Voltage Above Normal (Open/Short to High)
CAT-CID190-FMI8 serious
Engine Speed / Crankshaft Sensor - Abnormal Frequency, Pulse Width, or Period
Caterpillar Engine Versions
| Engine | Years | Applications | Notes |
|---|---|---|---|
| C7 | 2003-2009 | Peterbilt 335, Kenworth T370, IC Bus, Thomas school bus, F-650/F-750 | Medium-duty 7.2L. HEUI fuel injection. Largely replaced by PACCAR PX-9 / Cummins ISL after CAT exited on-highway in 2009. |
| C9 / C9.3 | 2003-2009 (on-highway) | Peterbilt 340, Kenworth T470, marine and industrial | 8.8L medium / heavy interface engine. ACERT after 2004. Still produced for off-highway / industrial. |
| C13 ACERT | 2004-2009 | Kenworth T800, Peterbilt 386, Freightliner Columbia, International 9200i | 12.5L on-highway big bore. Notorious EGR cooler failures and ACERT fuel system issues. |
| C15 ACERT | 2003-2009 | Kenworth W900, T800; Peterbilt 379, 389; Western Star 4900, 5900; Freightliner Classic XL | 15.2L flagship. Pre-ACERT C15 (2003-) was the legendary "old reliable"; ACERT version added EGR + variable geometry turbo and is the source of most CAT C15 fault codes. |
| C15 6NZ / MBN / BXS | 1999-2003 | Pre-ACERT semi truck installations | The non-EGR pre-ACERT 6NZ / MBN serial-prefix engines are still the gold standard for owner-operators -- minimal aftertreatment, maximum reliability. |
Common CAT Issues
- EGR cooler failures on C13 / C15 ACERT (coolant loss, white smoke, intake contamination)
- EGR venturi tube cracks -- runs hot, fatigues over time
- HEUI fuel pump failures on C7 / older C-series (high-pressure oil for unit injectors)
- Turbo actuator and VGT position sensor faults on ACERT-series
- NRS (NOx Reduction System) cooler failures on EPA10 ACERT engines
- Engine ECM grounding issues causing CID 168 voltage faults
- Common-rail injector faults on later C15 (CID 1-6 cylinder injector codes)