🔍 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.

232
Codes covered
20
Systems covered
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Fuel System

30 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
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

24 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

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

13 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
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
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

ABS / Brakes / Steering

12 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
C0775
Low
Tyre Pressure Monitoring System Sensor Malfunction
TPMS / Wheels
C0780
Low
Tyre Pressure Monitoring System Sensor — Low Battery
TPMS / Wheels
P0500
Medium
Vehicle Speed Sensor Malfunction
ABS / Driveline / Sensors

Battery / Charging

10 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
P0620
Medium
Generator 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

6 codes
B1000
High
Electronic Control Unit Internal 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

2 codes
P0A0F
High
Drive Motor A Temperature Too 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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