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Fault Codes

Browse published fault code pages with symptoms, causes, and fixes. Built for fast scanning and easy cross-linking across brands and engines.

SPN/FMI + OBDBrand/Engine mappingSEO-friendly slugsBuilt for scale
Published faults
151
Updated (7 days)
0
Brands
13
Engines
19
Search fault codes
Search by SPN/FMI (e.g. 5394 31 or SPN 5394 FMI 31), OBD codes (e.g. P0420), or keywords. Prefix works too (type 5 to see codes starting with 5).
Brand
Engine
Showing up to 200 most recently updated faults.
Code
Title
SPN 3563 FMI 9
Aftertreatment 1 intake NOx sensor abnormal update rate
SPN 168 FMI 3
Battery voltage high – charging system overvoltage
SPN 168 FMI 4
Battery voltage low – weak batteries, alternator, or poor connections
SPN 5398 FMI 31
DPF regeneration too frequent due to soot source – condition exists
SPN 3720 FMI 16
DPF soot load high – regen required soon
SPN 521049 FMI 31
Aftertreatment inducement active due to emissions fault – follow supporting codes
SPN 520371 FMI 31
DPF regeneration inhibited due to conditions – regen will not initiate
SPN 2799 FMI 7
DEF pump not responding – pump does not follow command
SPN 2799 FMI 5
DEF pump motor current low / open circuit
SPN 2799 FMI 31
DEF pump prime/pressure build fault – pressure not achieved
SPN 3515 FMI 4
EGR differential pressure voltage low – open circuit/short to ground
SPN 3515 FMI 2
EGR differential pressure signal erratic – unstable flow feedback
SPN 2631 FMI 4
Turbo actuator position low – signal lost / open circuit
SPN 2631 FMI 2
Turbo actuator position erratic – VGT control instability
SPN 523497 FMI 31
Aftertreatment diesel oxidation catalyst (DOC) performance condition exists
SPN 4363 FMI 7
SCR dosing valve not responding – command not followed
SPN 4363 FMI 5
SCR dosing valve current low / open circuit
SPN 4363 FMI 18
SCR dosing rate too low – DEF not injected as expected
SPN 3050 FMI 0
DPF ash load high – DPF service required
SPN 102 FMI 4
Boost pressure voltage low – open circuit/short to ground
SPN 102 FMI 3
Boost pressure voltage high – MAP/boost sensor circuit fault
SPN 3241 FMI 15
Aftertreatment 1 inlet temperature too low – SCR not reaching operating range
SPN 3242 FMI 15
Aftertreatment 1 outlet temperature too low during dosing
SPN 3226 FMI 20
Aftertreatment outlet NOx sensor drift – SCR efficiency calculations unreliable
SPN 520372 FMI 31
Aftertreatment regen inhibited – operating conditions not met
SPN 5397 FMI 31
DPF regeneration too frequent (condition exists)
SPN 3052 FMI 31
Misfire monitor condition exists (rough running complaint)
SPN 2623 FMI 3
Accelerator pedal channel 2 voltage high
SPN 5491 FMI 3
DEF line heater relay voltage high / short to power
SPN 5445 FMI 13
Engine throttle valve operation out of calibration
SPN 5394 FMI 7
DEF doser valve not responding
SPN 5394 FMI 5
DEF doser valve current low / open circuit
SPN 5376 FMI 4
Engine throttle valve temperature status voltage low
SPN 5376 FMI 3
Engine throttle valve temperature status voltage high
SPN 5016 FMI 4
ECU supply voltage low (power/ground problem causing random faults)
SPN 4795 FMI 31
DPF missing condition exists (hardware/config mismatch)
SPN 4752 FMI 18
EGR cooler efficiency below normal (soot/regens increase)
SPN 4360 FMI 2
SCR intake temperature signal erratic (sensor/connection)
SPN 4344 FMI 4
DEF line heater 3 voltage low / short to ground
SPN 4342 FMI 4
DEF line heater 2 voltage low / short to ground
SPN 4340 FMI 5
DEF line heater 1 current low / open circuit
SPN 4334 FMI 7
DEF dosing pressure not responding (system not responding)
SPN 4334 FMI 18
DEF dosing pressure below normal (weak pump or restriction)
SPN 4334 FMI 2
DEF dosing pressure data erratic (unstable signal)
SPN 3363 FMI 4
DEF tank heater voltage low / short to ground
SPN 3363 FMI 17
DEF tank heater below normal (weak heating)
SPN 1569 FMI 31
Engine protection torque derate active (follow the other codes)
SPN 3362 FMI 31
DEF dosing unit input lines condition exists (line/flow issue)
SPN 4364 FMI 18
SCR conversion efficiency below normal (inducement risk)
SPN 5394 FMI 31
DEF doser valve condition exists (sticking/crystallization)
SPN 108 FMI 3
Barometric pressure sensor voltage high – altitude reading error
SPN 3146 FMI 4
SCR outlet temperature sensor voltage low – open circuit
SPN 3146 FMI 3
SCR outlet temperature sensor voltage high – heater circuit issue
SPN 4485 FMI 31
EGR valve malfunction – mechanical fault exists
SPN 2633 FMI 7
Turbocharger VGT nozzle stuck – weak boost and lag
SPN 3568 FMI 9
DPF dosing temp sensor voltage high – soot burn temp anomaly
SPN 3610 FMI 4
DPF outlet pressure sensor voltage low – open circuit
SPN 3610 FMI 2
DPF outlet pressure sensor voltage above normal
SPN 3242 FMI 3
DPF intake gas temperature high – heated path fault
SPN 3318 FMI 2
DPF intake gas temp erratic – sensor data noise
SPN 4794 FMI 31
SCR catalyst system missing – condition exists
SPN 103 FMI 3
Air mass flow sensor voltage high – fuel mix errors
SPN 3265 FMI 9
DPF intake pressure too high – soot accumulation
SPN 3011 FMI 4
DPF pressure sensor voltage low – open circuit
SPN 3364 FMI 4
DEF quality sensor voltage below normal – incorrect DEF quality readings
SPN 3011 FMI 3
DPF pressure sensor voltage high – possible power short
SPN 179 FMI 4
Crankcase pressure low – ventilation concern
SPN 157 FMI 15
Fuel rail pressure not reached – injection enabling failed
SPN 5309 FMI 20
DPF outlet temp sensor data drift – readings not rational
SPN 3216 FMI 2
Intake NOx sensor circuit intermittent – data unstable
SPN 1127 FMI 7
Engine turbocharger boost pressure not responding – weak turbo
SPN 4321 FMI 3
Aftertreatment NOx catalyst inlet temp too high – catalyst stress
SPN 3226 FMI 4
Aftertreatment outlet NOx sensor voltage low – poor NOx data
SPN 3364 FMI 3
DEF quality sensor voltage high – possible short to power
SPN 157 FMI 10
Fuel rail pressure under capacity – injector enabling insufficient
SPN 3216 FMI 10
NOx sensor rationality fault – sensor disagreeing with expected values
SPN 84 FMI 4
Engine speed signal lost – no-start/stall risk
SPN 110 FMI 4
Intake air temperature sensor voltage low – open/short to ground
SPN 97 FMI 18
Oil pressure below normal – verify immediately
SPN 110 FMI 3
Intake air temperature sensor voltage high – incorrect temp reading
SPN 91 FMI 8
Accelerator pedal signal abnormal – hesitation or limp response
SPN 84 FMI 2
Engine speed signal erratic – crank sensor/wiring issue
SPN 157 FMI 18
Fuel rail pressure below commanded – derate/rough running
SPN 4094 FMI 18
EGR performance below normal – power loss, smoke, frequent regens
SPN 4334 FMI 16
DEF quality below threshold – contamination or sensor issue
SPN 102 FMI 16
Boost pressure below normal – charge air leak or restriction
SPN 94 FMI 16
Fuel delivery pressure below normal – restriction or weak lift pump
SPN 111 FMI 18
Coolant temperature below normal – thermostat stuck open
SPN 3251 FMI 4
DPF differential pressure voltage low – open circuit / short to ground
SPN 3251 FMI 3
DPF differential pressure voltage high – short to power / water in connector
SPN 3251 FMI 2
DPF differential pressure signal erratic – false restriction readings
SPN 3216 FMI 4
NOx sensor signal too low (inlet/upstream) – wiring or sensor failure
SPN 5319 FMI 31
DPF incomplete regeneration – regen did not finish
SPN 3713 FMI 31
Regen inhibited due to timeout – regen attempts not completing
SPN 3703 FMI 31
Active regeneration inhibited – inhibit switch/circuit active
SPN 3582
SCR conversion efficiency low – NOx reduction insufficient
SPN 3363 FMI 16
DEF tank heater above normal – heater control/circuit issue
SPN 3363 FMI 18
DEF tank heater below normal – heater not heating / open circuit
SPN 3719 FMI 16
DPF soot load too high – regen required / forced regen likely
SPN 5246 FMI 0
Aftertreatment derate active – inducement risk / 5 MPH threat
SPN 171 FMI 3
Ambient air temperature sensor voltage high – incorrect outside temperature reading
SPN 171 FMI 4
Ambient air temperature sensor voltage low – open circuit
SPN 108 FMI 18
Barometric pressure sensor below normal – altitude or sensor issue
SPN 100 FMI 18
Engine oil temperature above normal – cooling or lubrication concern
SPN 2659 FMI 0
Turbocharger boost pressure control error – overboost or underboost
SPN 2791 FMI 7
SCR dosing unit not responding – DEF delivery issue
SPN 3216 FMI 20
NOx sensor data drift detected – emissions efficiency compromised
SPN 94 FMI 3
Fuel delivery pressure sensor circuit voltage high – short to power / bad sensor signal
SPN 94 FMI 4
Fuel delivery pressure sensor circuit voltage low – hard starts, surging, power loss
SPN 157 FMI 7
Fuel rail pressure not responding – rough running, low power, possible no-start
3574
Aftertreatment DEF dosing issue (repeat occurrence, check contamination/debris)
1682
DEF system fault (repeat occurrence / contamination troubleshooting)
3596
Aftertreatment DEF dosing fault (repeat occurrence / contamination pattern)
SPN 3363 FMI 3
DEF tank heater voltage high (short to power / wiring fault)
SPN 1569 FMI 15
Engine Protection Torque Derate - Data Valid But Above Normal (Cummins)
SPN 3364 FMI 9
DEF Quality Sensor - Abnormal Update Rate / Communication Lost (Cummins X15)
SPN 5246 FMI 16
SCR Operator Inducement - Data Above Normal (Cummins, Detroit, Volvo)
SPN 5246 FMI 15
SCR Operator Inducement - Regulatory Fault Ignored (Cummins, Detroit, Volvo)
SPN 641 FMI 7
VGT Actuator - Mechanical Failure (Cummins ISX/X15, PACCAR, Volvo)
MID 128 PID 105 FMI 0
Intake Manifold Temperature - Too High (Volvo)
MID 128 PID 103 FMI 9
Turbocharger Speed Sensor - Signal Lost (Volvo)
MID 128 PID 103 FMI 1
Turbocharger Speed - Too Low (Volvo Underboost)
MID 128 PID 103 FMI 0
Turbocharger Speed - Too High (Volvo Overspeed)
MID 128 PID 102 FMI 3
Intake Manifold Pressure Sensor - Voltage High (Volvo)
MID 128 PID 102 FMI 1
Intake Manifold Pressure - Too Low (Volvo Underboost)
MID 128 PID 102 FMI 0
Intake Manifold Pressure - Too High (Volvo Turbo Overboost)
MID 128 PID 100 FMI 5
Engine Oil Pressure Sensor - Open Circuit (Volvo)
MID 128 PID 100 FMI 3
Engine Oil Pressure Sensor - Circuit High Voltage (Volvo)
MID 128 PID 100 FMI 1
Engine Oil Pressure Too Low (Volvo D11/D13/D16)
MID 128 PID 91 FMI 9
Accelerator Pedal Position - Update Rate (Volvo)
MID 128 PID 85 FMI 9
Cruise Control Status - Abnormal Update (Volvo)
MID 128 PID 84 FMI 9
Vehicle Speed - Abnormal Update Rate (Volvo)
MID 128 PID 81 FMI 12
Particulate Filter - Component Failure (Volvo)
MID 128 PID 81 FMI 5
Particulate Filter - Open Circuit (Volvo)
MID 128 PID 81 FMI 3
Particulate Filter - Voltage Above Normal (Volvo)
MID 128 PID 81 FMI 2
Particulate Filter - Signal Erratic (Volvo)
MID 128 PID 81 FMI 0
Particulate Filter - Pressure Above Normal (Volvo)
SPN 3719 FMI 31
DPF Differential Pressure - Signal Erratic
MID 128 PID 45 FMI 5
Preheater Relay - Open Circuit (Volvo)
MID 128 PID 45 FMI 4
Preheater Relay - Voltage Below Normal (Volvo)
MID 128 PID 45 FMI 3
Preheater Relay - Voltage Above Normal (Volvo)
MID 128 PID 26 FMI 3
Fan Speed Sensor - Voltage Above Normal (Volvo)
SPN 3719 FMI 31
DPF Differential Pressure - Signal Erratic
SPN 1569 FMI 0
NOx Sensor - Circuit Malfunction
SPN 4364 FMI 18
SCR Catalyst Efficiency Below Threshold
SPN 5394 FMI 31
DEF Dosing System Condition Exists
SPN 1234 FMI 12
Example Fault Title
SPN 5246 FMI 31
DEF Quality - Poor Quality Detected
SPN 1569 FMI 0
NOx Sensor - Circuit Malfunction
SPN 5246 FMI 31
DEF Quality - Poor Quality Detected
SPN 1234 FMI 12
Example Fault Title