The Cummins ISX engine series kept evolving between 2004 and 2006, bringing improved fuel economy, better emissions control, and reliable performance for heavy-duty fleets. Known for its strong EGR system and proven power, the ISX stayed a popular choice for long hauls and vocational trucks alike.
Having a quick reference for fault codes is still one of the best ways to cut downtime, reduce guesswork, and get trucks back on the road faster.
Cummins ISX (2004–2006) Engine Overview
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Displacement: 15.0L
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Horsepower Range: 400–600 HP
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Torque: Up to 2,050 lb-ft
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Emissions System: EGR
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Fuel System: Common Rail
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Applications: Freightliner Cascadia, Kenworth T600, Peterbilt 379, and other Class 8 trucks
📍 Get FREE Fault Code Information for all makes and models in Diesel Repair → Diesel Repair
Fault Codes for Cummins ISX (2004–2006)
Fault | PID | SPN | FMI | SID | Title
| Fault | PID | SPN | FMI | SID | Title |
| SPN 100 FMI 1 (415) | 100 | 100 | 1 | Engine Oil Pressure Low – Critical | |
| SPN 100 FMI 18 (143) | 100 | 100 | 18 | Engine Oil Pressure Low – Warning | |
| SPN 100 FMI 2 (435) | 100 | 100 | 2 | Engine Oil Pressure Sensor Circuit – Data Incorrect | |
| SPN 100 FMI 3 (135) | 100 | 100 | 3 | Engine Oil Pressure Sensor Circuit | |
| SPN 100 FMI 4 (141) | 100 | 100 | 4 | Engine Oil Pressure Sensor Circuit | |
| SPN 1029 FMI 4 (2374) | 95 | 1029 | 4 | Exhaust Gas Pressure Sensor Circuit | |
| SPN 102 FMI 2 (2973) | 102 | 102 | 2 | Intake Manifold Pressure | |
| SPN 102 FMI 2 (433) | 102 | 102 | 2 | Intake Manifold Pressure Sensor Circuit – Data Incorrect | |
| SPN 102 FMI 3 (122) | 102 | 102 | 3 | Intake Manifold Pressure Sensor Circuit | |
| SPN 102 FMI 4 (123) | 102 | 102 | 4 | Intake Manifold Pressure Sensor Circuit | |
| SPN 103 FMI 16 (595) | 103 | 103 | 16 | Turbocharger Number 1 Speed High Circuit | |
| SPN 103 FMI 18 (687) | 103 | 103 | 18 | Turbocharger Speed Low – Warning Level | |
| SPN 1043 FMI 3 (387) | 1043 | 3 | 221 | Accelerator Pedal Position Sensor Supply Voltage Circuit | |
| SPN 1043 FMI 4 (284) | 1043 | 4 | 221 | Engine Speed Sensor Supply Voltage Circuit | |
| SPN 1043 FMI 4 (443) | 1043 | 4 | 221 | Accelerator Pedal Position Sensor Supply Voltage Circuit | |
| SPN 105 FMI 0 (155) | 105 | 105 | Intake Manifold Air Temperature High – Critical | ||
| SPN 105 FMI 16 (2964) | 105 | 105 | 16 | Intake Manifold Air Temperature High – Warning | |
| SPN 105 FMI 3 (153) | 105 | 105 | 3 | Intake Manifold Air Temperature Sensor Circuit – Voltage Above Normal or Shorted to High Source | |
| SPN 105 FMI 4 (154) | 105 | 105 | 4 | Intake Manifold Air Temperature Sensor Circuit – Voltage Below Normal or Shorted to Low Source | |
| SPN 1072 FMI 3 (2366) | 1072 | 3 | 28 | Engine Brake Solenoid Number 1 Signal Circuit | |
| SPN 1072 FMI 3 (2366) | 1072 | 3 | 28 | Engine Brake Solenoid Number 1 Signal Circuit | |
| SPN 1072 FMI 3 (2367) | 1072 | 3 | 28 | Engine Brake Solenoid Number 2 Signal Circuit | |
| SPN 1072 FMI 3 (2367) | 1072 | 3 | 28 | Engine Brake Solenoid Number 2 Signal Circuit | |
| SPN 1072 FMI 4 (2362) | 1072 | 4 | 28 | Engine Brake Solenoid 1 Signal Circuit | |
| SPN 1073 FMI 4 (2363) | 1073 | 4 | 29 | Engine Brake Solenoid 2 Signal Circuit | |
| SPN 1079 FMI 3 (386) | 1079 | 3 | 232 | Sensor Supply Voltage Number 1 Circuit | |
| SPN 1079 FMI 4 (352) | 1079 | 4 | 232 | Sensor Supply Voltage Number 1 Circuit | |
| SPN 1080 FMI 4 (187) | 1080 | 4 | 232 | Sensor Supply Voltage Number 2 Circuit | |
| SPN 108 FMI 2 (295) | 108 | 108 | 2 | Barometric Pressure Sensor Circuit – Data Incorrect | |
| SPN 108 FMI 3 (221) | 108 | 108 | 3 | Barometric Pressure Sensor Circuit | |
| SPN 108 FMI 4 (222) | 108 | 108 | 4 | Barometric Pressure Sensor Circuit | |
| SPN 110 FMI 0 (151) | 110 | 110 | Engine Coolant Temperature High – Critical | ||
| SPN 110 FMI 16 (1119) | 110 | 110 | 16 | Engine Coolant Temperature – Data Valid But Above Normal Operating Range – Moderately Severe Level | |
| SPN 110 FMI 16 (2963) | 110 | 110 | 16 | Engine Coolant Temperature High – Warning | |
| SPN 110 FMI 3 (144) | 110 | 110 | 3 | Coolant Temperature Sensor Circuit – Voltage Above Normal or Shorted to High Source | |
| SPN 110 FMI 4 (145) | 110 | 110 | 4 | Coolant Temperature Sensor Circuit – Voltage Below Normal or Shorted to Low Source | |
| SPN 1112 FMI 3 (2368) | 1112 | 3 | 82 | Engine Brake Solenoid Number 3 Signal Circuit | |
| SPN 1112 FMI 4 (2365) | 1112 | 4 | 82 | Engine Brake Solenoid 3 Signal Circuit | |
| SPN 111 FMI 18 (197) | 111 | 111 | 18 | Engine Coolant Level Low – Warning | |
| SPN 111 FMI 3 (195) | 111 | 111 | 3 | Coolant Level Sensor 1 Circuit – Voltage Above Normal or Shorted to High Source | |
| SPN 111 FMI 3 (195) | 111 | 111 | 3 | Engine Coolant Level Sensor Circuit | |
| SPN 111 FMI 4 (196) | 111 | 111 | 4 | Coolant Level Sensor 1 Circuit – Voltage Below Normal or Shorted to Low Source | |
| SPN 111 FMI 4 (196) | 111 | 111 | 4 | Engine Coolant Level Sensor Circuit | |
| SPN 1172 FMI 3 (691) | 1172 | 3 | 151 | Turbocharger Number 1 Compressor Inlet Temperature Sensor Circuit – Voltage Above Normal or Shorted to High Source | |
| SPN 1172 FMI 4 (692) | 1172 | 4 | 151 | Turbocharger Number 1 Compressor Inlet Air Temperature Sensor Circuit – Voltage Below Normal or Shorted to Low Source | |
| SPN 1209 FMI 2 (2554) | 95 | 1209 | 2 | Exhaust Gas Pressure Sensor Circuit – Data Erratic, Intermittent, or Incorrect | |
| SPN 1209 FMI 3 (2373) | 95 | 1209 | 3 | Exhaust Gas Pressure Sensor Circuit | |
| SPN 1244 FMI 31 (2313) | 1244 | 31 | 83 | Rear Fueling Actuator Circuit | |
| SPN 1245 FMI 31 (2314) | 1245 | 31 | 84 | Rear Timing Actuator Circuit | |
| SPN 1265 FMI 3 (224) | 1265 | 3 | 85 | Centinel Oil Control Valve Circuit – Shorted High | |
| SPN 1265 FMI 4 (223) | 1265 | 4 | 85 | Centinel Oil Control Valve Circuit – Shorted Low | |
| SPN 1267 FMI 3 (338) | 1267 | 3 | 87 | Idle Shutdown Vehicle Accessories Relay Circuit | |
| SPN 1267 FMI 4 (339) | 1267 | 4 | 87 | Idle Shutdown Vehicle Accessories Relay Circuit | |
| SPN 1349 FMI 16 (2551) | 129 | 1349 | 16 | Fuel System Overfueling | |
| SPN 1349 FMI 18 (486) | 129 | 1349 | 18 | Fuel System Under-Fueling | |
| SPN 1378 FMI 31 (649) | 1378 | 31 | 153 | Engine Requires Lubricating Oil and Filter Change – Maintenance | |
| SPN 1380 FMI 17 (219) | 17 | 1380 | 17 | Centinel Oil Tank Level Low – Warning | |
| SPN 157 FMI 16 (2552) | 157 | 157 | 16 | Fuel System Over-fueling | |
| SPN 157 FMI 18 (559) | 157 | 157 | 18 | Fuel System Underfueling | |
| SPN 1590 FMI 2 (784) | 1590 | 2 | Adaptive Cruise Control Circuit | ||
| SPN 166 FMI 2 (951) | 166 | 166 | 2 | Cylinder Power Imbalance | |
| SPN 167 FMI 1 (598) | 167 | 167 | 1 | Battery Voltage Monitor – Very Low Voltage | |
| SPN 167 FMI 16 (596) | 167 | 167 | 16 | Battery Voltage Monitor – High Voltage | |
| SPN 167 FMI 18 (597) | 167 | 167 | 18 | Voltage Monitor – Low Voltage | |
| SPN 171 FMI 3 (249) | 171 | 171 | 3 | Ambient Air Temperature Sensor Circuit | |
| SPN 171 FMI 4 (256) | 171 | 171 | 4 | Ambient Air Temperature Sensor Circuit | |
| SPN 174 FMI 3 (263) | 174 | 174 | 3 | Engine Fuel Temperature Sensor Circuit – Voltage Above Normal or Shorted to High Source | |
| SPN 174 FMI 4 (265) | 174 | 174 | 4 | Engine Fuel Temperature Sensor Circuit – Voltage Below Normal or Shorted to Low Source | |
| SPN 175 FMI 0 (214) | 175 | 175 | Engine Oil Temperature High – Critical | ||
| SPN 175 FMI 3 (212) | 175 | 175 | 3 | Oil Temperature Sensor Circuit – Voltage Above Normal or Shorted to High Source | |
| SPN 175 FMI 4 (213) | 175 | 175 | 4 | Oil Temperature Sensor Circuit – Voltage Below Normal or Shorted to Low Source | |
| SPN 190 FMI 0 (234) | 190 | 190 | Engine Overspeed | ||
| SPN 190 FMI 2 (2321) | 190 | 190 | 2 | Engine Speed / Position Sensor Number 1 – Engine Speed / Position Glitch Detect | |
| SPN 190 FMI 2 (689) | 190 | 190 | 2 | Engine Speed Sensor Circuit | |
| SPN 19 FMI 19 (287) | 91 | 19 | 19 | SAE J1939 Data Link Multiplexing Accelerator Pedal Sensor | |
| SPN 19 FMI 19 (288) | 29 | 19 | 19 | SAE J1939 Data Link Multiplexing Remote Accelerator | |
| SPN 251 FMI 2 (319) | 251 | 251 | 2 | Real-Time Clock Power Circuit | |
| SPN 2789 FMI 15 (2346) | 2789 | 15 | Turbocharger Turbine Inlet Temperature (Calculated) – Data Above Normal Operational Range – Least Severe Level | ||
| SPN 2790 FMI 15 (2347) | 2790 | 15 | 309 | Turbocharger Compressor Outlet Air Temperature (Calculated) – Data Valid but Above Normal Range | |
| SPN 2791 FMI 15 (9121) | 2791 | 15 | 146 | EGR Valve Actuator Over Temperature (Calculated) – Data Above Normal Range | |
| SPN 2791 FMI 3 (2352) | 2791 | 3 | 146 | Exhaust Gas Recirculation (EGR) Valve Control Circuit – Voltage Above Normal or Shorted to High Source | |
| SPN 2791 FMI 4 (2351) | 2791 | 4 | 146 | Exhaust Gas Recirculation (EGR) Valve Control Circuit – Voltage Below Normal or Shorted to Low Source | |
| SPN 2791 FMI 5 (2349) | 2791 | 5 | 146 | Exhaust Gas Recirculation (EGR) Valve Control Circuit – Current Below Normal or Open Circuit | |
| SPN 2791 FMI 6 (2353) | 2791 | 6 | 146 | Exhaust Gas Recirculation (EGR) Valve Control Circuit – Excessive Current Detected | |
| SPN 2791 FMI 7 (2357) | 2791 | 7 | 146 | Exhaust Gas Recirculation (EGR) Valve Control – Mechanical System Not Responding Properly or Out of Adjustment | |
| SPN 2792 FMI 3 (2355) | 2792 | 3 | Turbocharger Control Shutoff Valve Circuit | ||
| SPN 2792 FMI 4 (2356) | 2792 | 4 | Turbocharger Control Shutoff Valve Circuit | ||
| SPN 27 FMI 13 (2348) | 27 | 27 | 13 | EGR Valve Self-Calibration | |
| SPN 27 FMI 2 (1228) | 27 | 27 | 2 | EGR Valve Position Sensor Circuit – Data Erratic, Intermittent, or Incorrect | |
| SPN 27 FMI 3 (2271) | 27 | 27 | 3 | EGR Valve Position Sensor Circuit | |
| SPN 27 FMI 4 (2272) | 27 | 27 | 4 | EGR Valve Position Circuit – Voltage Below Normal or Shorted to Low Source | |
| SPN 3555 FMI 17 (1943) | 3555 | 17 | Ambient Air Density – Data Valid but Below Normal Operational Range – Least Severe Level | ||
| SPN 411 FMI 16 (2359) | 411 | 411 | 16 | EGR Differential Pressure Sensor – Data Valid But Above Normal Operating Range – Moderately Severe Level | |
| SPN 411 FMI 3 (2273) | 411 | 411 | 3 | EGR Valve Differential Pressure Sensor Circuit | |
| SPN 411 FMI 4 (2274) | 411 | 411 | 4 | EGR Differential Pressure Sensor Circuit | |
| SPN 412 FMI 15 (2961) | 412 | 412 | 15 | EGR Temperature – Data Valid But Above Normal Operating Range | |
| SPN 412 FMI 16 (2962) | 412 | 412 | 16 | EGR Temperature – Data Valid But Above Normal Operating Range | |
| SPN 412 FMI 3 (2375) | 412 | 412 | 3 | Recirculated Exhaust Gas Temperature Sensor Circuit – Voltage Above Normal or Shorted to High Source | |
| SPN 412 FMI 4 (2376) | 412 | 412 | 4 | Recirculated Exhaust Gas Temperature Sensor Circuit – Voltage Below Normal or Shorted to Low Source | |
| SPN 558 FMI 13 (432) | 558 | 13 | 230 | Accelerator Pedal Idle Validation Circuit | |
| SPN 558 FMI 2 (431) | 558 | 2 | 230 | Accelerator Pedal Idle Validation Circuit | |
| SPN 558 FMI 2 (431) | 558 | 2 | 230 | Accelerator Pedal Idle Validation Circuit | |
| SPN 558 FMI 2 (431) | 558 | 2 | 230 | Accelerator Pedal Idle Validation Circuit | |
| SPN 558 FMI 4 (551) | 558 | 4 | 230 | Accelerator Pedal Idle Validation Circuit | |
| SPN 558 FMI 4 (551) | 558 | 4 | 230 | Accelerator Pedal Idle Validation Circuit | |
| SPN 558 FMI 4 (551) | 558 | 4 | 230 | Accelerator Pedal Idle Validation Circuit | |
| SPN 620 FMI 3 (227) | 620 | 3 | 232 | Sensor Supply Voltage Number 2 Circuit | |
| SPN 627 FMI 2 (434) | 627 | 2 | 251 | Unswitched Battery Supply Circuit | |
| SPN 629 FMI 12 (111) | 629 | 12 | 254 | Electronic Control Module (ECM) Microprocessor | |
| SPN 629 FMI 12 (343) | 629 | 12 | 254 | Electronic Control Module (ECM) | |
| SPN 630 FMI 2 (341) | SID 253 | 630 | 2 | Unswitched Battery Supply Circuit | |
| SPN 632 FMI 3 (255) | 632 | 3 | 17 | Engine Fuel Shutoff Valve Drive Circuit – Voltage Above Normal or Shorted to High Source | |
| SPN 632 FMI 4 (254) | 632 | 4 | 17 | Fuel Shutoff Valve Circuit | |
| SPN 632 FMI 7 (259) | 632 | 7 | 17 | Fuel Shutoff Valve | |
| SPN 633 FMI 31 (2311) | 633 | 31 | 18 | Front Fueling Actuator Circuit | |
| SPN 635 FMI 31 (2312) | 635 | 31 | 20 | Front Timing Actuator Circuit | |
| SPN 639 FMI 13 (286) | 639 | 13 | 231 | SAE J1939 Data Link Multiplexing | |
| SPN 639 FMI 2 (426) | 639 | 2 | 231 | SAE J1939 Data Link Communication | |
| SPN 639 FMI 9 (285) | 231 | 639 | 9 | SAE J1939 Data Link Multiplexing | |
| SPN 641 FMI 3 (2277) | 641 | 3 | 27 | Variable Geometry Turbocharger Output Device Driver – Shorted High | |
| SPN 641 FMI 3 (2385) | 641 | 3 | 27 | Variable Geometry Turbocharger Actuator Driver Circuit – Voltage Above Normal or Shorted to High Source | |
| SPN 641 FMI 4 (2278) | 641 | 4 | 27 | Turbocharger Control Valve Circuit | |
| SPN 641 FMI 4 (2384) | 641 | 4 | 27 | Variable Geometry Turbocharger Actuator Driver Circuit – Voltage Below Normal or Shorted to Low Source | |
| SPN 647 FMI 3 (2377) | 647 | 3 | 33 | Fan Control Circuit – Shorted High | |
| SPN 647 FMI 4 (245) | 647 | 4 | 33 | Fan Control Circuit | |
| SPN 677 FMI 3 (584) | 677 | 3 | 39 | Starter Relay Circuit | |
| SPN 677 FMI 4 (585) | 677 | 4 | 39 | Starter Relay Circuit | |
| SPN 723 FMI 2 (778) | 723 | 2 | 64 | Camshaft Position Sensor Circuit | |
| SPN 723 FMI 7 (731) | 723 | 7 | 64 | Engine Speed Sensor and Camshaft Position Sensor – Mechanical Misalignment Between Camshaft and Crankshaft Sensors | |
| SPN 84 FMI 10 (242) | 84 | 84 | 10 | Vehicle Speed Sensor Circuit | |
| SPN 84 FMI 2 (241) | 84 | 84 | 2 | Vehicle Speed Sensor Circuit | |
| SPN 91 FMI 3 (131) | 91 | 91 | 3 | Accelerator Pedal Position Sensor Circuit | |
| SPN 91 FMI 4 (132) | 91 | 91 | 4 | Accelerator Pedal Position Sensor Circuit | |
| SPN 94 FMI 16 (449) | 94 | 94 | 16 | High Fuel Pressure | |
| SPN 94 FMI 18 (2215) | 94 | 94 | 18 | Fuel Pump Delivery Pressure – Data Valid but Below Normal Operating Range – Moderately Severe Level | |
| SPN 94 FMI 18 (482) | 94 | 94 | 18 | Fuel Pressure Low – Data Valid but Below Normal Operating Range – Moderately Severe Level | |
| SPN 94 FMI 3 (546) | 94 | 94 | 3 | Rail Fuel Pressure Sensor Circuit | |
| SPN 94 FMI 4 (547) | 94 | 94 | 4 | Rail Fuel Pressure Sensor Circuit | |
| SPN 95 FMI 16 (2372) | 95 | 95 | 16 | Fuel Filter Restriction Moderately High – Warning | |
| SPN 974 FMI 3 (133) | 29 | 974 | 3 | Remote Accelerator Pedal or Lever Position Sensor Circuit | |
| SPN 974 FMI 4 (134) | 29 | 974 | 4 | Remote Accelerator Pedal or Lever Position Sensor Circuit | |
| SPN 97 FMI 15 (418) | 97 | 97 | 15 | Water-in-Fuel Indicator High – Maintenance | |
| SPN 97 FMI 3 (428) | 97 | 97 | 3 | Water-in-Fuel Sensor Circuit – Voltage Above Normal or Shorted to High Source | |
| SPN 97 FMI 4 (429) | 97 | 97 | 4 | Water-in-Fuel Sensor Circuit – Voltage Below Normal or Shorted to Low Source |
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