ECU General Malfunction
B0001 means the body control module has detected an internal hardware or software fault. Multiple body electrical systems may stop working.
Front Left Side Airbag Circuit
B0010 means the airbag control module has detected a fault in the driver's side front airbag deployment circuit. The airbag may not deploy.
Right Front Pretensioner Circuit
B0028 means the airbag module detected a fault in the passenger-side seatbelt pretensioner circuit. The pretensioner may not fire in a crash.
Rear RH Side Crash Sensor
B0051 means the airbag module detected a fault in the right rear side impact crash sensor. Side airbags may not deploy properly in a crash.
Electronic Frontal Sensor 1
B0100 means the airbag module detected a fault in the primary front crash sensor. Frontal airbags may not deploy correctly in a collision.
Climate Control Push Button Circuit
B1200 means the HVAC control module detected a fault in the climate control panel push button circuit. A/C or heat controls may not respond.
Battery Voltage Low
B1318 means the body control module is detecting battery voltage below the acceptable threshold. Electrical systems may behave erratically.
Ground Circuit Open
B1325 means the body control module has detected an open ground connection in the body electrical system, causing unpredictable electrical faults.
PATS Received Incorrect Key Code
B1600 means Ford's Passive Anti-Theft System received a key code that doesn't match any programmed keys. The vehicle may not start.
Transponder Key Not Identified
B2799 means the immobilizer system cannot identify the key transponder. The engine will crank but not start. Common on Toyota and Lexus.
Left Front Wheel Speed Sensor Circuit
C0035 means the ABS module detects a fault in the left front wheel speed sensor circuit. ABS and traction control are disabled until repaired.
Right Front Wheel Speed Sensor Circuit
C0040 means the ABS module detects a fault in the right front wheel speed sensor circuit. ABS and traction control are disabled until repaired.
Left Rear Wheel Speed Sensor Circuit
C0045 means the ABS module detects a fault in the left rear wheel speed sensor circuit. ABS and stability control are disabled until repaired.
Right Rear Wheel Speed Sensor Circuit
C0050 means the ABS module detects a fault in the right rear wheel speed sensor circuit. ABS and stability control are disabled until repaired.
Pump Motor Circuit
C0110 indicates a fault in the ABS pump motor circuit. The hydraulic pump cannot build or maintain brake pressure for ABS and stability control.
PCM Indicated TCS Malfunction
C0242 means the ABS module received a traction control disable signal from the PCM due to an engine control system fault.
EBCM Relay Circuit
C0265 indicates a fault in the Electronic Brake Control Module relay circuit. ABS, traction, and stability control are disabled.
Rear Speed Sensor Malfunction
C0300 indicates a rear wheel speed sensor malfunction. ABS and stability control are affected until the sensor circuit is repaired.
ECU Malfunction
C0550 indicates an internal malfunction in the chassis electronic control unit. ABS, traction control, and stability control are all disabled.
Engine Control System Malfunction
C1201 is a Toyota/Lexus code meaning the engine control system has a fault that disables VSC and traction control. Fix the engine code first.
Intake Camshaft Position Actuator Circuit (Bank 1)
P0010 indicates a problem in the variable valve timing (VVT) solenoid circuit on Bank 1. Common causes include a faulty VVT solenoid, wiring issues, or low oil.
Intake Camshaft Timing Over-Advanced (Bank 1)
P0011 means the intake camshaft on Bank 1 is more advanced than the PCM commanded. Common causes are dirty oil, a stuck VVT solenoid, or a worn timing chain.
Intake Camshaft Timing Over-Retarded (Bank 1)
P0012 means the intake camshaft on Bank 1 is more retarded than commanded. Common causes include dirty oil, a stuck VVT solenoid, or worn timing components.
Crankshaft/Camshaft Position Correlation (Bank 1 Sensor A)
P0016 means the crankshaft and camshaft positions are out of expected correlation on Bank 1. Often caused by a stretched timing chain or VVT issues.
HO2S Heater Control Circuit (Bank 1 Sensor 1)
P0030 means the heater circuit in the upstream oxygen sensor on Bank 1 has failed. Usually a bad O2 sensor, blown fuse, or wiring issue.
Mass Air Flow (MAF) Circuit
P0100 means the PCM has detected a general malfunction in the mass air flow sensor circuit. The MAF sensor measures how much air enters the engine so the PCM ca
Mass Air Flow Range/Performance
P0101 means the MAF sensor's readings fall outside the expected range for the current engine RPM and throttle position. The sensor is communicating, but its num
Mass Air Flow Low Input
P0102 means the MAF sensor signal is lower than the PCM expects for current operating conditions. The sensor is reporting too little airflow — either because th
Mass Air Flow High Input
P0103 means the MAF sensor signal is higher than the PCM expects for current operating conditions. The sensor is reporting too much airflow — typically because
MAP/BARO Pressure Circuit Range/Performance
P0106 means the manifold absolute pressure (MAP) sensor reading doesn't match what the PCM expects for current engine RPM, throttle position, and load. The sens
Intake Air Temperature (IAT) High Input
P0113 means the intake air temperature sensor signal indicates an extremely high temperature — usually because the circuit has an open connection, not because t
Engine Coolant Temperature Circuit
P0115 means there's a general fault in the engine coolant temperature (ECT) sensor circuit. The PCM is getting a signal from the ECT sensor that's out of its ex
Engine Coolant Temperature Range/Performance
P0116 means the engine coolant temperature (ECT) sensor readings don't match the expected warm-up pattern. The PCM compares ECT data against intake air temperat
Engine Coolant Temperature Low Input
P0117 means the ECT sensor voltage signal is too low, indicating a coolant temperature below -40°F — a reading that's physically impossible under normal conditi
Engine Coolant Temperature High Input
P0118 means the ECT sensor voltage signal is too high, indicating a coolant temperature of approximately -40°F or lower — a physically impossible reading under
Throttle Position Sensor Range/Performance
P0121 means the throttle position sensor (TPS) signal is erratic or outside the expected range for current engine conditions. The most common causes are a fault
Throttle Position Sensor Circuit Low Input
P0122 means the throttle position sensor (TPS) voltage has dropped below the minimum expected threshold — typically below 0.2V. The most common causes are a wir
Throttle Position Sensor Circuit High Input
P0123 means the throttle position sensor (TPS) voltage has exceeded the maximum expected threshold — typically above 4.8V. The most common causes are a wiring s
Insufficient Coolant Temperature for Closed Loop Fuel Control
P0125 means the engine coolant isn't reaching the temperature the PCM needs to enter closed-loop fuel control within a reasonable time. In open loop, the PCM ru
Coolant Thermostat Temperature Below Regulating Temperature
P0128 means the engine is not reaching normal operating temperature fast enough. The most common cause is a stuck-open thermostat (75% of cases), followed by a
O2 Sensor Circuit (Bank 1, Sensor 1)
P0130 means the PCM detected a general fault in the upstream oxygen sensor circuit on Bank 1. This sensor is the primary air-fuel ratio feedback sensor — it tel
O2 Sensor Low Voltage (Bank 1, Sensor 1)
P0131 means the upstream O2 sensor on Bank 1 is reporting a voltage below 0.1V for an extended period, indicating a persistent lean signal. This can mean the se
O2 Sensor High Voltage (Bank 1, Sensor 1)
P0132 means the upstream O2 sensor on Bank 1 is reporting a voltage above 0.9V for an extended period, indicating a persistent rich signal. This can mean the en
O2 Sensor Slow Response (Bank 1, Sensor 1)
P0133 means the upstream O2 sensor on Bank 1 is switching between lean and rich readings more slowly than the PCM expects. A healthy sensor transitions in under
O2 Sensor No Activity Detected (Bank 1, Sensor 1)
P0134 means the upstream O2 sensor on Bank 1 shows no voltage activity — it's not switching between lean and rich at all. The sensor is either completely dead (
O2 Sensor Heater Circuit (Bank 1, Sensor 1)
P0135 means the heater circuit in the upstream oxygen sensor on Bank 1 has failed. O2 sensors need to reach 600°F+ to work accurately — the internal heater gets
O2 Sensor Heater Circuit (Bank 1, Sensor 2)
P0141 means the heater circuit in the downstream O2 sensor on Bank 1 (the post-catalytic-converter sensor) has failed. The downstream sensor monitors catalytic
O2 Sensor Heater Circuit (Bank 2, Sensor 1)
P0155 means the heater circuit in the upstream oxygen sensor on Bank 2 has failed. This is the Bank 2 equivalent of P0135. The most common cause is a burned-out
O2 Sensor Heater Circuit (Bank 2, Sensor 2)
P0161 means the heater circuit in the downstream O2 sensor on Bank 2 has failed. This is the Bank 2 post-catalytic-converter sensor, used to monitor converter e
Fuel Trim Malfunction (Bank 1)
P0170 means the PCM has detected that Bank 1 fuel trims are outside their acceptable operating range — the engine can't maintain the correct air-fuel ratio with
System Too Lean (Bank 1)
P0171 means the engine's air-fuel mixture on Bank 1 is too lean — too much air or not enough fuel. The most common causes are vacuum leaks (35%), a dirty or fai
System Too Rich (Bank 1)
P0172 means the engine is running too rich on Bank 1 — too much fuel or not enough air. The most common causes are a faulty O2 sensor sending false lean signals
System Too Lean (Bank 2)
P0174 means the engine's air-fuel mixture on Bank 2 is too lean — too much air or not enough fuel. If P0171 (Bank 1 lean) is also present, the cause is in a sys
System Too Rich (Bank 2)
P0175 means the engine is running too rich on Bank 2 — too much fuel or not enough measured air. If P0172 (Bank 1 rich) is also present, the cause is shared bet
Engine Overtemperature Condition
P0217 means the engine coolant temperature has exceeded safe limits. Pull over immediately. Common causes are low coolant, a bad thermostat, or a failed water pump.
Turbocharger/Supercharger Underboost
P0299 means the turbo or supercharger is not producing expected boost pressure. Common causes are boost leaks, a sticking wastegate, or a worn turbo.
Random/Multiple Cylinder Misfire Detected
P0300 means the PCM detected misfires occurring across multiple cylinders rather than a single cylinder. The most common causes are worn spark plugs or ignition
Cylinder 1 Misfire Detected
P0301 means the PCM detected repeated misfires specifically in cylinder 1. The most common causes are a worn spark plug (35%), a failing ignition coil (30%), an
Cylinder 2 Misfire Detected
P0302 means the PCM detected repeated misfires in cylinder 2. The diagnostic approach is identical to any single-cylinder misfire: check spark plug, ignition co
Cylinder 3 Misfire Detected
P0303 means the PCM detected repeated misfires in cylinder 3. The most common causes are a worn spark plug (35%), a failing ignition coil (30%), and a faulty fu
Cylinder 4 Misfire Detected
P0304 means the PCM detected repeated misfires in cylinder 4. The most common causes are a worn spark plug (35%), a failing ignition coil (30%), and a faulty fu
Cylinder 5 Misfire Detected
P0305 means the PCM detected repeated misfires in cylinder 5. This code only appears on 5+ cylinder engines (V6, V8, inline-5, inline-6). The diagnostic approac
Cylinder 6 Misfire Detected
P0306 means the PCM detected repeated misfires in cylinder 6. This code appears only on 6+ cylinder engines. The diagnostic approach is identical to other singl
Camshaft Position Sensor Circuit
P0340 means the PCM is not receiving a valid signal from the camshaft position sensor. Common causes are a bad sensor, wiring issues, or timing problems.
Camshaft Position Sensor Range/Performance
P0341 means the camshaft position sensor signal is present but out of expected range. Common causes are a failing sensor, timing issues, or wiring problems.
Exhaust Gas Recirculation (EGR) Flow Malfunction
P0400 means the PCM detected a general fault in the EGR system — exhaust gas recirculation flow is not what the PCM expects. The most common causes are clogged
Exhaust Gas Recirculation (EGR) Insufficient Flow
P0401 means the PCM detected that the EGR valve is not flowing enough exhaust gas back into the intake manifold. The most common cause is a clogged EGR valve or
Catalyst System Efficiency Below Threshold (Bank 1)
P0420 indicates the catalytic converter on Bank 1 is not reducing emissions efficiently enough. The most common cause is a failing catalytic converter (45% of c
Catalyst System Efficiency Below Threshold (Bank 2)
P0430 is the Bank 2 version of P0420 — the catalytic converter on the opposite side of a V-engine is not reducing emissions efficiently enough. The most common
Evaporative Emission System Malfunction
P0440 is a general EVAP system fault code — the PCM detected a problem with the vapor recovery system but can't narrow it to a specific leak size or component.
EVAP System Incorrect Purge Flow
P0441 means the PCM detected that the EVAP purge valve isn't flowing the expected amount of fuel vapor from the charcoal canister to the intake manifold. The mo
Evaporative Emission System Small Leak Detected
P0442 means the PCM found a small leak in the EVAP system — the sealed vapor recovery system connected to your fuel tank. The most common cause is a worn gas ca
EVAP Purge Control Valve Circuit
P0443 means the PCM detected an electrical fault in the EVAP purge valve circuit — not a leak, but a problem with the valve's wiring, connector, or internal sol
EVAP Purge Control Valve Circuit Shorted
P0445 means the EVAP purge control valve circuit has a short. Usually caused by a faulty purge valve, damaged wiring, or a connector issue.
EVAP System Vent Control Circuit
P0446 means the PCM detected a fault in the EVAP vent valve circuit — the valve that allows fresh air into the charcoal canister during purge cycles and seals t
Evaporative Emission System Large Leak Detected
P0455 means the PCM detected a large leak in the EVAP system, which captures fuel vapor from the gas tank to prevent it from escaping into the atmosphere. The m
EVAP System Very Small Leak Detected
P0456 indicates the smallest detectable leak in the EVAP system — smaller than what triggers P0442 (small leak). These tiny leaks are almost impossible to find
Idle Control System
P0505 means the PCM has detected a general fault in the idle speed control system — the engine isn't idling at the commanded speed or the idle control mechanism
Idle Control System RPM Lower Than Expected
P0506 means the engine is idling lower than the PCM's target — typically 100+ RPM below the expected idle speed. The most common causes are a dirty or stuck IAC
Idle Control System RPM Higher Than Expected
P0507 means the engine is idling higher than the PCM expects — typically 200+ RPM above the target idle speed. The most common causes are a vacuum leak (40%), a
System Voltage Low
P0562 means the PCM is detecting system voltage below the normal operating range. Common causes are a failing alternator, weak battery, or corroded connections.
Serial Communication Link
P0600 indicates an internal communication failure within the PCM or between the PCM and other modules. Often requires professional diagnosis.
Transmission Control System Malfunction
P0700 is a generic informational code indicating the transmission control module (TCM) has stored a fault code. P0700 itself doesn't identify the problem — it's
Input/Turbine Speed Sensor Circuit
P0715 means the transmission control module (TCM) can't read the input shaft (turbine) speed sensor signal. This sensor tells the TCM how fast the torque conver
Output Speed Sensor Circuit
P0720 means the transmission control module (TCM) can't read the output shaft speed sensor signal. This sensor measures how fast the transmission's output shaft
Incorrect Gear Ratio
P0730 means the transmission control module (TCM) detected that the actual gear ratio — calculated by comparing input shaft speed to output shaft speed — doesn'
Torque Converter Clutch Solenoid Circuit
P0740 is an electrical circuit code indicating a fault in the torque converter clutch (TCC) solenoid circuit. The TCM detected an open, short, or out-of-range s
Torque Converter Clutch Solenoid Performance/Stuck Off
P0741 means the TCM commanded the torque converter clutch (TCC) to lock up, but the expected RPM drop didn't happen — the converter is slipping when it should b
Shift Solenoid A Malfunction
P0750 indicates a fault in shift solenoid A — the first shift solenoid in the transmission's hydraulic control system. The TCM detected an electrical or functio
Post Catalyst Fuel Trim Too Lean (Bank 1)
P2096 means the air-fuel mixture downstream of the catalytic converter on Bank 1 is too lean. Often caused by exhaust leaks, a failing cat, or O2 sensor issues.
Throttle/Pedal Position Sensor Correlation
P2135 means the throttle position sensors disagree with each other. The vehicle enters limp mode with severely reduced power. Requires prompt diagnosis.
System Too Lean at Idle (Bank 1)
P2187 means the engine is running lean specifically at idle on Bank 1. Common causes are vacuum leaks, PCV issues, and dirty fuel injectors.
High Speed CAN Communication Bus
U0001 indicates a fault on the high-speed CAN bus backbone. Multiple modules may lose communication, triggering cascading codes.
Lost Communication with ECM/PCM
U0100 means the vehicle has lost communication with the engine control module. Engine management is compromised — do not drive.
Lost Communication with TCM
U0101 means the vehicle lost communication with the transmission control module. Transmission may enter limp mode or shift erratically.
Lost Communication with Anti-Lock Brake System (ABS) Module
U0121 means the vehicle lost communication with the ABS module. Anti-lock brakes, traction control, and stability control are disabled.
Lost Communication with Body Control Module (BCM)
U0140 means the vehicle lost communication with the body control module. Lighting, locks, windows, and other body systems may be affected.
Lost Communication with Instrument Panel Cluster (IPC)
U0155 means the vehicle lost communication with the instrument cluster. Gauges, warning lights, and odometer may be inoperative.
Lost Communication with HVAC Control Module
U0164 means the vehicle lost communication with the climate control module. A/C, heater, and blower functions may be inoperative.
Lost Communication with Hybrid/EV Powertrain Control Module
U0293 means the vehicle lost communication with the hybrid/EV control module. Electric drive may be disabled. High-voltage system involved.
Invalid Data Received from ECM/PCM
U0401 means a module received corrupt or out-of-range data from the engine control module. Engine behavior may be unpredictable.
CAN Communication Bus Fault
U1000 is a manufacturer-specific CAN bus fault, especially common on Nissan/Infiniti. Often stored alongside other DTCs as a companion code.
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