OBD-II Fault Code Cross-Reference
Every diagnostic trouble code (DTC), cross-referenced across all vehicles in our database. Find which makes and models trigger each code, the most common cause on each platform, and the confirmed fix. Each code links to its own page covering ranked causes, severity, diagnosis, and what drives the repair cost.
Look up a fault code
Enter a diagnostic trouble code (e.g. P0301, P0171) to get a printable diagnostic report: definition, severity, the most common causes across our 300-vehicle database, and a DIY vs. shop decision aid.
- DTC definitions: OBD-II diagnostic trouble code definitions follow SAE J2012 / ISO 15031-6 naming (P0xxx powertrain codes). Definitions shown per vehicle are maintained in the VehCalc 300-vehicle database.
- Cross-vehicle frequency: Cause ranking above is computed live from the VehCalc 300-vehicle database (retrieved 2026-08-20) — how often each cause phrase appears across the models that trigger this code. It is a statistical guide, not a per-vehicle diagnosis.
- Cost guidance: Planning ranges only. Verify all parts and labor costs with local suppliers and a written shop estimate before approving any repair.
B124E
mediumHVAC Coolant Pump Control Circuit
Coolant pump failure affecting battery thermal management
B124E causes, symptoms & diagnosis →
BMS_a103
highBattery Management System Communication Error
BMS to vehicle gateway CAN bus fault
BMS_a103 causes, symptoms & diagnosis →
C1201
lowEngine Control System Malfunction
Communication fault between ECM and skid control ECU
C1201 causes, symptoms & diagnosis →
C1241
mediumLow Battery Positive Voltage
Weak 12V auxiliary battery or alternator failure
C1241 causes, symptoms & diagnosis →
C1391
lowPositive Acceleration Sensor Circuit Malfunction
VSC sensor calibration or wiring issue
C1391 causes, symptoms & diagnosis →
DI_a115
highDrive Inverter Fault
Rear drive unit inverter MOSFET failure
DI_a115 causes, symptoms & diagnosis →
P0011
mediumCamshaft Position A - Timing Over-Advanced (Bank 1)
Dirty VCT phaser / oil control valve
P0011 causes, symptoms & diagnosis →
P0014
mediumCamshaft Position Timing Over-Advanced (Bank 1)
OCV (Oil Control Valve) sticking
P0014 causes, symptoms & diagnosis →
P0016
highCrankshaft-Camshaft Position Correlation (Bank 1)
VCT phaser wear or timing chain stretch (3.5L EcoBoost)
P0016 causes, symptoms & diagnosis →
P0026
mediumIntake Valve Control Solenoid Circuit Range/Performance (Bank 1)
AVCS oil control solenoid failure
P0026 causes, symptoms & diagnosis →
P0117
mediumEngine Coolant Temperature Circuit Low
Electric water pump failure (EA888 common)
P0117 causes, symptoms & diagnosis →
P0128
lowCoolant Thermostat Below Regulating Temperature
Stuck-open thermostat or low coolant
P0128 causes, symptoms & diagnosis →
P0171
mediumSystem Too Lean (Bank 1)
Dirty MAF sensor, cracked intake boot, PCV valve leak
P0171 causes, symptoms & diagnosis →
P0174
mediumSystem Too Lean (Bank 2)
Dirty MAF sensor or cracked intake tube
P0174 causes, symptoms & diagnosis →
P0234
highTurbocharger/Supercharger Overboost Condition
Wastegate actuator sticking, turbo control solenoid
P0234 causes, symptoms & diagnosis →
P0299
mediumTurbocharger/Supercharger Underboost
Wastegate rattle, cracked charge pipe, degraded turbo
P0299 causes, symptoms & diagnosis →
P0300
highRandom/Multiple Cylinder Misfire Detected
Worn ignition coils, fouled spark plugs, carbon buildup
P0300 causes, symptoms & diagnosis →
P0351
mediumIgnition Coil A Primary/Secondary Circuit
Ignition coil pack failure on cylinder 1
P0351 causes, symptoms & diagnosis →
P0420
lowCatalyst System Efficiency Below Threshold (Bank 1)
Aging catalytic converter or degraded rear O2 sensor
P0420 causes, symptoms & diagnosis →
P0421
highWarm Up Catalyst Efficiency Below Threshold (Bank 1)
Catalyst degradation from oil contamination
P0421 causes, symptoms & diagnosis →
P0430
mediumCatalyst System Efficiency Below Threshold (Bank 2)
Catalytic converter aging or exhaust leak upstream
P0456
lowEVAP System Very Small Leak Detected
Loose or faulty fuel cap, cracked EVAP line
P0456 causes, symptoms & diagnosis →
P0520
mediumEngine Oil Pressure Sensor/Switch Circuit
Oil pressure sensor failure
P0520 causes, symptoms & diagnosis →
P0521
highEngine Oil Pressure Sensor/Switch Range/Performance
Debris from lifter failure clogging oil pickup
P061B
highInternal Engine Control Module Torque Performance
PCM internal fault or software corruption
P061B causes, symptoms & diagnosis →
P0741
mediumTorque Converter Clutch Performance
CVT/9-speed converter wear
P0741 causes, symptoms & diagnosis →
P0A01
mediumHybrid Battery Charger Temperature Sensor Circuit
Battery thermal sensor failure
P0A01 causes, symptoms & diagnosis →
P0A7F
mediumHybrid Battery Pack Deterioration
Cell aging, thermal stress
P0A7F causes, symptoms & diagnosis →
P0A80
highReplace Hybrid Battery Pack
HV battery cell degradation exceeding capacity threshold
P0A80 causes, symptoms & diagnosis →
P0AA6
highHybrid Battery Isolation Fault
Insulation breakdown in HV battery
P0AA6 causes, symptoms & diagnosis →
P0AFA
highHV Battery System Voltage Low
12V battery failure preventing contactor closure
P0AFA causes, symptoms & diagnosis →
P0D61
highDrive Motor Inverter Performance
Inverter overheating, coolant pump failure
P0D61 causes, symptoms & diagnosis →
P12C2
highCoolant Pump 2 Switching Off
Electric coolant pump failure
P12C2 causes, symptoms & diagnosis →
P1326
highEngine Management System - Knock Sensor Detection
Connecting rod bearing wear (Hyundai/Kia 2.5L)
P1450
mediumFan Speed Performance
Cooling fan module or fan clutch failure
P1450 causes, symptoms & diagnosis →
P1E00
mediumHV Battery Module Voltage Differential
Degraded battery cell module
P1E00 causes, symptoms & diagnosis →
P2015
mediumIntake Manifold Runner Position Sensor (Bank 1)
Intake manifold runner flap motor failure
P2015 causes, symptoms & diagnosis →
P2440
highSecondary Air Injection System Switching Valve Stuck Open
Air injection pump and switching valve failure
P2440 causes, symptoms & diagnosis →
P2459
mediumDiesel Particulate Filter Regeneration Frequency
Short-trip duty cycles preventing DPF burn-off
P253400
high48V On-Board System Voltage Malfunction
ISG (Integrated Starter Generator) failure on mild-hybrid
P25A2
highEngine Control Module Power Relay Control Circuit
ECM relay or fuse box connection issue
P25A2 causes, symptoms & diagnosis →
P3400
mediumValve Pause System (Bank 1)
VCM system oil pressure switch failure
P3400 causes, symptoms & diagnosis →
U0100
mediumLost Communication With ECM/PCM A
Software instability, gateway module reboot
U0100 causes, symptoms & diagnosis →
VCSEC_a166
mediumVehicle Controller Security System Error
VCSEC module internal fault or 12V battery low
VCSEC_a166 causes, symptoms & diagnosis →
Data sources & how to use this page
- DTC definitions: OBD-II diagnostic trouble code definitions follow SAE J2012 / ISO 15031-6 naming (P0xxx powertrain codes). Vehicle-specific descriptions are maintained in the VehCalc 300-vehicle database.
- Cross-reference: The "vehicles" list shows every model in our database that stores this code, with each model's own common-cause and fix notes in its dedicated guide.
- Retrieval date: Database snapshot 2026-08-20. Codes and causes can vary by model year and engine; always verify against the vehicle's own scan-tool data and service manual.
Diagnostic reference only — not repair advice. Fault-code information on this page is provided for educational and planning purposes. It does not replace an inspection by a qualified mechanic or the vehicle manufacturer's service information. Before repairing a vehicle you rely on, consult a certified technician (e.g. an ASE-certified mechanic). Cost figures, where shown, are planning estimates — verify with local written quotes.