Diagnostics
OBD-II Code Lookup
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P0087serious
Fuel Rail/System Pressure Too Low
- Restricted fuel filter
- Weak lift/supply pump
- Failing high-pressure (CP) pump
P0088serious
Fuel Rail/System Pressure Too High
- Stuck fuel pressure regulator / control valve
- Faulty fuel rail pressure sensor
- Wiring short to the regulator
P0093serious
Fuel System Large Leak Detected
- Leaking injector or injector return
- Cracked high-pressure line
- Failed high-pressure pump seal
P1093serious
Fuel Rail Pressure Low During Power Enrichment
- Weak CP3/CP4 pump
- Air in the fuel
- Restricted fuel supply or filter
P0101watch
MAF Sensor Range/Performance
- Dirty or contaminated MAF sensor
- Intake (boost) leak before the sensor
- Restricted air filter
P0102watch
MAF Sensor Circuit Low Input
- Failed MAF sensor
- Open or shorted MAF wiring
- Corroded connector
P0106watch
MAP/Barometric Pressure Sensor Range/Performance
- Soot-clogged MAP/boost sensor
- Boost leak
- Vacuum/pressure line fault
P0128watch
Coolant Temp Below Thermostat Regulating Temperature
- Stuck-open thermostat
- Failing coolant temperature sensor
- Low coolant level
P0171watch
System Too Lean (Bank 1)
- Intake/boost leak (unmetered air)
- Weak fuel supply
- Dirty MAF
P0234serious
Turbocharger Overboost Condition
- Stuck VGT vanes (carbon)
- Boost control / actuator fault
- Stuck wastegate
P0299serious
Turbocharger Underboost Condition
- Boost leak (cracked CAC hose, loose clamp)
- Sticking VGT vanes
- Clogged intercooler
P0046watch
Turbo Boost Control Circuit Range/Performance
- Faulty boost control solenoid/actuator
- Carboned VGT mechanism
- Wiring/connector fault
P226Cwatch
Turbocharger Boost Control 'A' Slow Response
- Carboned, sticking VGT vanes
- Worn actuator
- Soot/coking in the turbine housing
P2262serious
Turbo Boost Pressure Not Detected (Mechanical)
- Seized/sticking VGT vanes
- Large boost leak
- Turbo failure
P0300serious
Random/Multiple Cylinder Misfire Detected
- Injector fault on multiple cylinders
- Low compression
- Fuel delivery problem
P0301serious
Cylinder 1 Misfire Detected
- Faulty injector on that cylinder
- Low compression in that cylinder
- Glow plug failure (cold)
P0401watch
EGR Flow Insufficient Detected
- Carbon-clogged EGR valve or cooler
- Stuck EGR valve
- Soot in the intake
P0402watch
EGR Flow Excessive Detected
- EGR valve stuck open
- DPFE / EGR sensor fault
- Carbon holding the valve open
P0404watch
EGR Control Circuit Range/Performance
- Carbon-bound EGR valve
- Faulty EGR position sensor
- Actuator/wiring fault
P0420watch
Catalyst System Efficiency Below Threshold (Bank 1)
- Aged or failed catalyst
- Oxygen sensor fault
- Exhaust leak
P0470watch
Exhaust Pressure Sensor Fault
- Soot-clogged EBP sensor or tube
- Wiring/connector fault
- Sensor failure
P0488watch
EGR Throttle Position Control Range/Performance
- Carboned intake throttle valve
- Throttle actuator fault
- Wiring issue
P2002serious
Diesel Particulate Filter Efficiency Below Threshold (Bank 1)
- Loaded or cracked DPF
- DPF pressure sensor fault
- Failed/incomplete regens
P2463serious
Diesel Particulate Filter Soot Accumulation
- Incomplete regens (short trips)
- Pressure sensor fault
- Excess soot from an upstream issue
P242Fserious
Diesel Particulate Filter Restriction — Ash Accumulation
- High-mileage ash load (normal accumulation)
- Oil consumption adding ash
- Pressure sensor fault
P2452watch
Diesel Particulate Filter Pressure Sensor Circuit
- Failed DPF pressure sensor
- Clogged sensor hoses
- Wiring/connector fault
P2459watch
Diesel Particulate Filter Regeneration Frequency
- Short-trip driving (regens interrupted)
- Excess soot from EGR over-flow or a boost leak
- Injector issue
P204Fserious
Reductant (DEF) System Performance
- Poor or contaminated DEF
- Dosing system fault
- NOx sensor issue
P207Fserious
Reductant (DEF) Quality Performance
- Contaminated or old DEF
- Wrong fluid added
- DEF quality sensor fault
P20E8serious
Reductant (DEF) Pressure Too Low
- DEF pump fault
- Frozen or clogged DEF lines/injector
- Air in the DEF system
P229Ewatch
NOx Sensor Performance (Downstream)
- Failed NOx sensor
- Wiring/connector fault
- Underlying SCR/dosing problem
P0380watch
Glow Plug/Heater Circuit 'A' Malfunction
- Failed glow plug(s)
- Glow plug control module
- Relay or wiring fault
P0540info
Intake Air Heater Circuit
- Grid heater relay fault
- Heater element failure
- Wiring issue
P0670watch
Glow Plug Module Control Circuit
- Failed glow plug control module (GPCM)
- Wiring between ECM and module
- Power/ground fault
P0683info
Glow Plug Module to ECM Communication Circuit
- Wiring/connector fault between ECM and GPCM
- Failed glow plug module
- Corrosion at connectors
P0335serious
Crankshaft Position Sensor Circuit
- Failed crank position sensor
- Damaged reluctor/tone ring
- Wiring/connector fault
P0340watch
Camshaft Position Sensor Circuit
- Failed cam position sensor
- Wiring/connector fault
- Damaged sensor tone ring
P0606serious
ECM/PCM Processor Fault
- Power or ground fault to the ECM
- Corroded connectors
- Failing ECM
P0521watch
Engine Oil Pressure Sensor/Switch Range/Performance
- Failed oil pressure sensor
- Wiring fault
- Genuinely low oil pressure
P0562watch
System Voltage Low
- Failing alternator
- Weak battery or connections
- Corroded grounds
P0700watch
Transmission Control System (MIL Request)
- A stored transmission fault (read TCM codes)
- Transmission sensor/solenoid issue
- Low or degraded fluid
P0868serious
Transmission Fluid Pressure Low
- Low transmission fluid
- Worn pump or seals
- Pressure control solenoid fault
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