🔍 OBD-II Reference

OBD Fault Code Reference

Every fault code explained — symptoms, possible causes, whether it's safe to drive and MOT impact. UK-focused, plain English.

248
Codes covered
20
Systems covered
Free
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Fuel System

32 codes
P0087
High
Fuel Rail / System Pressure Too Low
Fuel System
P0088
High
Fuel Rail / System Pressure Too High
Fuel System
P0090
Medium
Fuel Pressure Regulator 1 Control Circuit Malfunction
Fuel System
P0093
High
Fuel System Leak Detected — Large
Fuel System
P0171
Medium
System Too Lean — Bank 1
Fuel / Air System
P0172
Medium
System Too Rich — Bank 1
Fuel / Air System
P0174
Medium
System Too Lean — Bank 2
Fuel / Air System
P0175
Medium
System Too Rich — Bank 2
Fuel / Air System
P0176
Low
Fuel Composition Sensor Circuit Malfunction
Fuel / Sensors
P0177
Low
Fuel Composition Sensor Circuit Low
Fuel / Sensors
P0178
Low
Fuel Composition Sensor Circuit High
Fuel / Sensors
P0190
Medium
Fuel Rail Pressure Sensor Circuit Malfunction
Fuel System / Sensors
P0191
Medium
Fuel Rail Pressure Sensor Range / Performance
Fuel System / Sensors
P0192
Medium
Fuel Rail Pressure Sensor Low Input
Fuel System / Sensors
P0193
Medium
Fuel Rail Pressure Sensor High Input
Fuel System / Sensors
P0194
Medium
Fuel Rail Pressure Sensor Intermittent
Fuel System / Sensors
P0201
High
Injector Circuit / Open — Cylinder 1
Fuel Injectors
P0202
High
Injector Circuit / Open — Cylinder 2
Fuel Injectors
P0203
High
Injector Circuit / Open — Cylinder 3
Fuel Injectors
P0204
High
Injector Circuit / Open — Cylinder 4
Fuel Injectors
P0205
High
Injector Circuit / Open — Cylinder 5
Fuel Injectors
P0206
High
Injector Circuit / Open — Cylinder 6
Fuel Injectors
P0261
High
Cylinder 1 Injector Circuit Low
Fuel Injectors
P0262
High
Cylinder 1 Injector Circuit High
Fuel Injectors
P0263
High
Cylinder 2 Injector Circuit Low
Fuel Injectors
P0264
High
Cylinder 2 Injector Circuit High
Fuel Injectors
P0267
High
Cylinder 3 Injector Circuit Low
Fuel Injectors
P0268
High
Cylinder 3 Injector Circuit High
Fuel Injectors
P0271
High
Cylinder 4 Injector Circuit Low
Fuel Injectors
P0272
High
Cylinder 4 Injector Circuit High
Fuel Injectors
P2187
Medium
System Too Lean at Idle — Bank 1
Fuel / Air System
P2188
Medium
System Too Rich at Idle — Bank 1
Fuel / Air System

Air / Intake

26 codes
P0100
Medium
Mass Air Flow Sensor Circuit Malfunction
Air Intake / Sensors
P0101
Medium
Mass Air Flow Sensor Range / Performance Problem
Air Intake / Sensors
P0102
Medium
Mass Air Flow Sensor Low Input
Air Intake / Sensors
P0103
Medium
Mass Air Flow Sensor High Input
Air Intake / Sensors
P0105
Medium
Manifold Absolute Pressure / Barometric Pressure Circuit Malfunction
Air Intake / Sensors
P0106
Medium
Manifold Absolute Pressure Sensor Range / Performance
Air Intake / Sensors
P0107
Medium
Manifold Absolute Pressure Sensor Low Input
Air Intake / Sensors
P0108
Medium
Manifold Absolute Pressure Sensor High Input
Air Intake / Sensors
P0110
Low
Intake Air Temperature Sensor Circuit Malfunction
Air Intake / Sensors
P0112
Low
Intake Air Temperature Sensor Low Input
Air Intake / Sensors
P0113
Low
Intake Air Temperature Sensor High Input
Air Intake / Sensors
P0120
Medium
Throttle Position Sensor Circuit Malfunction
Throttle / Accelerator
P0121
Medium
Throttle Position Sensor Range / Performance Problem
Throttle / Accelerator
P0122
Medium
Throttle Position Sensor Low Input
Throttle / Accelerator
P0123
Medium
Throttle Position Sensor High Input
Throttle / Accelerator
P0505
Medium
Idle Air Control System Malfunction
Idle / Throttle Control
P0506
Medium
Idle Speed Control — RPM Lower Than Expected
Idle / Throttle Control
P0507
Medium
Idle Speed Control — RPM Higher Than Expected
Idle / Throttle Control
P2100
High
Throttle Actuator Control Motor Circuit Open
Throttle / Drive-by-Wire
P2101
High
Throttle Actuator Control Motor Circuit Range / Performance
Throttle / Drive-by-Wire
P2111
High
Throttle Actuator Control System — Stuck Open
Throttle / Drive-by-Wire
P2112
High
Throttle Actuator Control System — Stuck Closed
Throttle / Drive-by-Wire
P2135
High
Throttle / Pedal Position Sensor Correlation Fault
Throttle / Accelerator
P2227
Low
Barometric Pressure Sensor Circuit Range / Performance
Air / Atmospheric Sensors
P2228
Medium
Barometric Pressure Sensor Circuit Low
Air / Atmospheric Sensors
P2229
Medium
Barometric Pressure Sensor Circuit High
Air / Atmospheric Sensors

Exhaust / O2 Sensors

21 codes
P0030
Low
Heated Oxygen Sensor Heater Control Circuit — Bank 1 Sensor 1
O2 Heater Circuit
P0031
Low
Heated Oxygen Sensor Heater Control Circuit Low — Bank 1 Sensor 1
O2 Heater Circuit
P0036
Low
Heated Oxygen Sensor Heater Control Circuit — Bank 1 Sensor 2
O2 Heater Circuit
P0130
Medium
O2 Sensor Circuit Malfunction — Bank 1 Sensor 1
Exhaust / Sensors
P0131
Medium
O2 Sensor Circuit Low Voltage — Bank 1 Sensor 1
Exhaust / Sensors
P0132
Medium
O2 Sensor Circuit High Voltage — Bank 1 Sensor 1
Exhaust / Sensors
P0133
Medium
O2 Sensor Circuit Slow Response — Bank 1 Sensor 1
Exhaust / Sensors
P0136
Medium
O2 Sensor Circuit Malfunction — Bank 1 Sensor 2
Exhaust / Sensors
P0137
Medium
O2 Sensor Circuit Low Voltage — Bank 1 Sensor 2
Exhaust / Sensors
P0138
Medium
O2 Sensor Circuit High Voltage — Bank 1 Sensor 2
Exhaust / Sensors
P0139
Low
O2 Sensor Circuit Slow Response — Bank 1 Sensor 2
Exhaust / Sensors
P0141
Low
O2 Sensor Heater Circuit Malfunction — Bank 1 Sensor 2
Exhaust / Sensors
P0150
Medium
O2 Sensor Circuit Malfunction — Bank 2 Sensor 1
Exhaust / Sensors
P0151
Medium
O2 Sensor Circuit Low Voltage — Bank 2 Sensor 1
Exhaust / Sensors
P0152
Medium
O2 Sensor Circuit High Voltage — Bank 2 Sensor 1
Exhaust / Sensors
P0153
Medium
O2 Sensor Circuit Slow Response — Bank 2 Sensor 1
Exhaust / Sensors
P0155
Low
O2 Sensor Heater Circuit Malfunction — Bank 2 Sensor 1
O2 Heater Circuit
P0156
Medium
O2 Sensor Circuit Malfunction — Bank 2 Sensor 2
Exhaust / Sensors
P0157
Medium
O2 Sensor Circuit Low Voltage — Bank 2 Sensor 2
Exhaust / Sensors
P0158
Medium
O2 Sensor Circuit High Voltage — Bank 2 Sensor 2
Exhaust / Sensors
P0161
Low
O2 Sensor Heater Circuit Malfunction — Bank 2 Sensor 2
O2 Heater Circuit

Catalyst / Emissions

15 codes
P0069
Medium
Manifold Absolute Pressure — Barometric Pressure Correlation
Air Intake / Sensors
P0410
Low
Secondary Air Injection System Malfunction
Emissions / Air System
P0411
Low
Secondary Air Injection System Incorrect Flow
Emissions / Air System
P0412
Low
Secondary Air Injection System Switching Valve Circuit
Emissions / Air System
P0420
Medium
Catalyst System Efficiency Below Threshold — Bank 1
Exhaust / Emissions
P0430
Medium
Catalyst System Efficiency Below Threshold — Bank 2
Exhaust / Emissions
P1000
Low
OBD Systems Readiness Test Not Complete
OBD / Emissions
P2047
Medium
Reductant Injector Circuit Open — Bank 1
SCR / AdBlue System
P2048
Medium
Reductant Injector Circuit Low — Bank 1
SCR / AdBlue System
P2096
Medium
Post Catalyst Fuel Trim System Too Lean — Bank 1
Exhaust / Emissions
P2097
Medium
Post Catalyst Fuel Trim System Too Rich — Bank 1
Exhaust / Emissions
P20EE
Medium
SCR NOx Catalyst Efficiency Below Threshold — Bank 1
SCR / AdBlue System
P225C
Medium
Reductant Quality System Performance
SCR / AdBlue System
P2279
Medium
Intake Air System Leak
Air Intake System
P2BAD
Medium
Reductant Quality Performance — Poor Quality Detected
SCR / AdBlue System

DPF / Diesel

10 codes
P0471
Medium
Exhaust Pressure Sensor Range / Performance
Exhaust / DPF Sensors
P0472
Medium
Exhaust Pressure Sensor Circuit Low
Exhaust / DPF Sensors
P0545
Medium
Exhaust Gas Temperature Sensor Circuit Low — Bank 1 Sensor 1
Exhaust Temperature / DPF
P0546
Medium
Exhaust Gas Temperature Sensor Circuit High — Bank 1 Sensor 1
Exhaust Temperature / DPF
P2002
Medium
Diesel Particulate Filter Efficiency Below Threshold — Bank 1
DPF / Emissions
P244A
Medium
Diesel Particulate Filter Differential Pressure Too Low
DPF / Sensors
P244B
High
Diesel Particulate Filter Differential Pressure Too High
DPF / Sensors
P2453
Medium
Diesel Particulate Filter Pressure Sensor Circuit Range / Performance
DPF / Sensors
P2454
Medium
Diesel Particulate Filter Pressure Sensor Circuit Low
DPF / Sensors
P2455
Medium
Diesel Particulate Filter Pressure Sensor Circuit High
DPF / Sensors

Engine Timing / VVT

14 codes
P0010
Medium
Intake Camshaft Position Actuator Circuit — Bank 1
Variable Valve Timing
P0011
Medium
Intake Camshaft Position Over-Advanced — Bank 1
Variable Valve Timing
P0012
Medium
Intake Camshaft Position Timing Over-Retarded — Bank 1
Variable Valve Timing
P0016
High
Crankshaft / Camshaft Position Correlation Fault — Bank 1
Engine Timing
P0017
High
Crankshaft / Camshaft Position Correlation Fault — Bank 1 Exhaust
Engine Timing
P0020
Medium
Intake Camshaft Position Actuator Circuit — Bank 2
Variable Valve Timing
P0021
Medium
Intake Camshaft Position Over-Advanced — Bank 2
Variable Valve Timing
P0022
Medium
Intake Camshaft Position Timing Over-Retarded — Bank 2
Variable Valve Timing
P0325
Medium
Knock Sensor 1 Circuit Malfunction — Bank 1
Engine / Sensors
P0326
Medium
Knock Sensor 1 Circuit Range / Performance — Bank 1
Engine / Sensors
P0330
Medium
Knock Sensor 2 Circuit Malfunction — Bank 2
Engine / Sensors
P0335
High
Crankshaft Position Sensor Circuit Malfunction
Engine Timing / Sensors
P0340
High
Camshaft Position Sensor Circuit Malfunction — Bank 1
Engine Timing / Sensors
P0345
High
Camshaft Position Sensor Circuit Malfunction — Bank 2
Engine Timing / Sensors

Transmission

19 codes
P0700
Medium
Transmission Control System Malfunction
Automatic Transmission
P0705
Medium
Transmission Range Sensor Circuit Malfunction — Park / Neutral
Automatic Transmission
P0706
Medium
Transmission Range Sensor Circuit Range / Performance
Automatic Transmission
P0710
Medium
Transmission Fluid Temperature Sensor Circuit Malfunction
Automatic Transmission
P0711
Low
Transmission Fluid Temperature Sensor Range / Performance
Automatic Transmission
P0712
Low
Transmission Fluid Temperature Sensor Low Input
Automatic Transmission
P0713
Low
Transmission Fluid Temperature Sensor High Input
Automatic Transmission
P0715
Medium
Input / Turbine Shaft Speed Sensor Circuit Malfunction
Automatic Transmission
P0720
Medium
Output Shaft Speed Sensor Circuit Malfunction
Automatic Transmission
P0725
Medium
Engine Speed Input Circuit Malfunction
Automatic Transmission / Engine
P0730
Medium
Incorrect Gear Ratio
Automatic Transmission
P0740
Medium
Torque Converter Clutch Circuit Malfunction
Automatic Transmission
P0741
Medium
Torque Converter Clutch Circuit Performance / Stuck Off
Automatic Transmission
P0742
High
Torque Converter Clutch Circuit Stuck On
Automatic Transmission
P0750
Medium
Shift Solenoid A Malfunction
Automatic Transmission
P0755
Medium
Shift Solenoid B Malfunction
Automatic Transmission
P0760
Medium
Shift Solenoid C Malfunction
Automatic Transmission
P0801
Medium
Reverse Inhibit Control Circuit Malfunction
Automatic Transmission
P0850
Low
Park / Neutral Switch Input Circuit Malfunction
Automatic Transmission

ABS / Brakes / Steering

14 codes
C0031
High
Right Front Wheel Speed Sensor Circuit Malfunction
ABS / Wheel Speed Sensors
C0034
High
Right Rear Wheel Speed Sensor Circuit Malfunction
ABS / Wheel Speed Sensors
C0035
High
Front Right Wheel Speed Sensor Circuit Malfunction
ABS / Wheel Speed Sensors
C0037
High
Left Rear Wheel Speed Sensor Circuit Malfunction
ABS / Wheel Speed Sensors
C0040
High
Front Left Wheel Speed Sensor Circuit Malfunction
ABS / Wheel Speed Sensors
C0044
High
Left Front Wheel Speed Sensor Circuit Range / Performance
ABS / Wheel Speed Sensors
C0051
High
Right Rear Wheel Speed Sensor Circuit Range / Performance
ABS / Wheel Speed Sensors
C0455
High
Steering Wheel Angle Sensor Circuit Range / Performance
Steering / ESC
C0460
High
Steering Wheel Angle Sensor Circuit Malfunction
Steering / ESC
C0710
High
Steering Position Signal Malfunction
Steering / ESC
C0775
Low
Tyre Pressure Monitoring System Sensor Malfunction
TPMS / Wheels
C0780
Low
Tyre Pressure Monitoring System Sensor — Low Battery
TPMS / Wheels
C0750
Low
Tyre Pressure Monitor Sensor Not Transmitting
TPMS / Wheels
P0500
Medium
Vehicle Speed Sensor Malfunction
ABS / Driveline / Sensors

Battery / Charging

13 codes
P0560
Medium
System Voltage Malfunction
Battery / Charging System
P0562
Medium
System Voltage Low
Battery / Charging System
P0563
Medium
System Voltage High
Battery / Charging System
P0615
Medium
Starter Relay Circuit Malfunction
Starting System
P0616
Medium
Starter Relay Circuit Low
Starting System
P0617
Medium
Starter Relay Circuit High
Starting System
P0620
Medium
Generator Control Circuit Malfunction
Battery / Charging System
P0621
Low
Generator Lamp Control Circuit Malfunction
Battery / Charging System
P0650
Low
Malfunction Indicator Lamp Control Circuit Malfunction
Electrical / Lighting
P0A7E
High
High Voltage Battery Temperature Too High
Hybrid Battery System
P0A80
High
Replace Hybrid Battery Pack
Hybrid Battery System
P2503
Medium
Charging System Voltage Low
Battery / Charging System
P2504
Medium
Charging System Voltage High
Battery / Charging System

ECU / Module Faults

7 codes
B1000
High
Electronic Control Unit Internal Fault
ECU / Module Fault
B1001
Medium
ECU / Module Supply Voltage Fault
ECU / Module Fault
P0601
High
Engine Control Module Memory Check Sum Error
ECU / Module Fault
P0602
High
Control Module Programming Error
ECU / Module Fault
P0605
High
Internal Control Module ROM Error
ECU / Module Fault
P0606
High
ECU / PCM Processor Fault
ECU / Module Fault
U0300
High
Software Incompatibility With ECM / PCM
Module Compatibility

CAN Bus / Communication

10 codes
U0001
High
High Speed CAN Communication Bus Fault
CAN Bus / Communication
U0028
High
Vehicle Communication Bus A Malfunction
CAN Bus / Communication
U0073
High
Control Module Communication Bus A Off
CAN Bus / Communication
U0074
High
Control Module Communication Bus B Off
CAN Bus / Communication
U0100
High
Lost Communication With ECM / PCM
CAN Bus / Communication
U0101
High
Lost Communication With TCM
CAN Bus / Communication
U0121
High
Lost Communication With ABS Control Module
CAN Bus / Communication
U0140
Medium
Lost Communication With Body Control Module
CAN Bus / Communication
U0155
Medium
Lost Communication With Instrument Panel Cluster
CAN Bus / Communication
U0415
High
Invalid Data Received From Anti-Lock Brake System Control Module
CAN Bus / Communication

Hybrid / Electric

3 codes
P0A0F
High
Drive Motor A Temperature Too High
Hybrid / EV System
P0A07
High
Drive Motor Current High
Hybrid / EV System
P3000
High
High Voltage Battery Malfunction
Hybrid / EV System

Glow Plugs / Diesel Cold Start

7 codes
P0380
Medium
Glow Plug / Heater Circuit A Malfunction
Diesel / Cold Start
P0381
Low
Glow Plug / Heater Indicator Circuit Malfunction
Diesel / Cold Start
P0540
Low
Intake Air Heater Circuit Malfunction
Diesel / Cold Start
P0671
Medium
Cylinder 1 Glow Plug Circuit Malfunction
Diesel / Cold Start
P0672
Medium
Cylinder 2 Glow Plug Circuit Malfunction
Diesel / Cold Start
P0673
Medium
Cylinder 3 Glow Plug Circuit Malfunction
Diesel / Cold Start
P0674
Medium
Cylinder 4 Glow Plug Circuit Malfunction
Diesel / Cold Start
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