AutoSense AI Knowledge Base
Understand car problems before they become expensive repairs.
Browse plain-English guides to common check engine codes, vehicle symptoms, likely causes, severity, and typical repair cost ranges.
Knowledge Guide
P0420 Code: Catalyst System Efficiency Below Threshold
A practical guide to the P0420 check engine code, catalytic converter efficiency, symptoms, causes, and repair cost ranges.
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Knowledge Guide
P0171 Code: System Too Lean Bank 1
P0171 means the engine is running too lean on bank 1, often from extra air, not enough fuel, or incorrect sensor data.
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Knowledge Guide
P0300 Code: Random or Multiple Cylinder Misfire
P0300 means the engine computer detected random misfires across multiple cylinders.
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Knowledge Guide
Engine Misfire Symptoms, Causes, and Repair Cost
A misfire happens when one or more cylinders fail to burn fuel correctly, causing shaking, power loss, and potential converter damage.
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Knowledge Guide
Bad Battery Symptoms: Early Warning Signs
A weak battery can cause slow starts, clicking, warning lights, and intermittent electrical problems.
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Knowledge Guide
Bad Alternator Symptoms: Charging System Warning Signs
A failing alternator can cause battery warning lights, dim lights, stalling, and repeated dead batteries.
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Knowledge Guide
Oxygen Sensor Failure Symptoms, Causes, and Repair Cost
A failing oxygen sensor can affect fuel mixture, emissions, fuel economy, and catalyst efficiency codes.
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Knowledge Guide
Coolant Temperature High: Symptoms, Causes, and Repair Cost
High coolant temperature can point to cooling system problems that may damage the engine if ignored.
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Knowledge Guide
Rough Idle: Symptoms, Causes, and Repair Cost
A rough idle can come from air, fuel, ignition, sensor, or mechanical issues.
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Knowledge Guide
Poor Fuel Economy: Common Causes and Repair Cost
Poor fuel economy can come from driving conditions, maintenance, sensors, fuel mixture problems, or engine faults.
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Knowledge Guide
P0101 Code: Mass Air Flow Circuit Range/Performance
P0101 means the engine computer sees airflow readings that do not match expected engine load. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0113 Code: Intake Air Temperature Sensor 1 Circuit High
P0113 means the intake air temperature signal is higher than expected, often from an open circuit or sensor issue. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0128 Code: Coolant Temperature Below Thermostat Regulating Temperature
P0128 means the engine is taking too long to reach normal operating temperature. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0135 Code: Oxygen Sensor Heater Circuit Malfunction Bank 1 Sensor 1
P0135 means the upstream oxygen sensor heater circuit is not warming the sensor as expected. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0141 Code: Oxygen Sensor Heater Circuit Malfunction Bank 1 Sensor 2
P0141 means the downstream oxygen sensor heater circuit is not warming the catalyst-monitoring sensor as expected. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0172 Code: System Too Rich Bank 1
P0172 means bank 1 is receiving too much fuel or not enough air. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0174 Code: System Too Lean Bank 2
P0174 means bank 2 is getting too much air or not enough fuel. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0175 Code: System Too Rich Bank 2
P0175 means bank 2 is receiving too much fuel or not enough air. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0301 Code: Cylinder 1 Misfire Detected
P0301 means cylinder 1 is not completing combustion consistently. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0302 Code: Cylinder 2 Misfire Detected
P0302 means cylinder 2 is not completing combustion consistently. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0303 Code: Cylinder 3 Misfire Detected
P0303 means cylinder 3 is not completing combustion consistently. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0304 Code: Cylinder 4 Misfire Detected
P0304 means cylinder 4 is not completing combustion consistently. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0305 Code: Cylinder 5 Misfire Detected
P0305 means cylinder 5 is not completing combustion consistently. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0306 Code: Cylinder 6 Misfire Detected
P0306 means cylinder 6 is not completing combustion consistently. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0325 Code: Knock Sensor 1 Circuit Malfunction Bank 1
P0325 means the knock sensor circuit is not reporting engine knock information correctly. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0335 Code: Crankshaft Position Sensor A Circuit Malfunction
P0335 means the engine computer is losing or not trusting crankshaft position data. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0340 Code: Camshaft Position Sensor A Circuit Malfunction
P0340 means the engine computer is not receiving a reliable camshaft position signal. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0401 Code: Exhaust Gas Recirculation Flow Insufficient Detected
P0401 means the EGR system is not flowing enough exhaust gas. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0430 Code: Catalyst System Efficiency Below Threshold Bank 2
P0430 means bank 2 catalyst efficiency appears below the expected range. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0440 Code: Evaporative Emission Control System Malfunction
P0440 means the EVAP system has a general vapor control fault. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0441 Code: EVAP Control System Incorrect Purge Flow
P0441 means the purge flow through the EVAP system is not what the ECM expects. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0442 Code: EVAP Control System Leak Detected Small Leak
P0442 means the EVAP system detected a small fuel vapor leak. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0446 Code: EVAP Vent Control Circuit Malfunction
P0446 means the EVAP vent control circuit or vent valve is not operating correctly. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0455 Code: EVAP Control System Leak Detected Gross/Large Leak
P0455 means the EVAP system detected a large fuel vapor leak. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0456 Code: EVAP Control System Leak Detected Very Small Leak
P0456 means the EVAP system detected a very small fuel vapor leak. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0500 Code: Vehicle Speed Sensor A Malfunction
P0500 means the engine computer is missing or receiving unreliable vehicle speed data. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0505 Code: Idle Air Control System Malfunction
P0505 means the idle control system cannot regulate idle speed correctly. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0506 Code: Idle Control System RPM Lower Than Expected
P0506 means idle speed is lower than the computer expects. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0507 Code: Idle Control System RPM Higher Than Expected
P0507 means idle speed is higher than the computer expects. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0562 Code: System Voltage Low
P0562 means vehicle system voltage is lower than expected. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0011 Code: A Camshaft Position Timing Over-Advanced or System Performance Bank 1
P0011 means variable valve timing is more advanced than expected on bank 1. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0012 Code: A Camshaft Position Timing Over-Retarded Bank 1
P0012 means variable valve timing is more retarded than expected on bank 1. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0606 Code: ECM/PCM Processor Fault
P0606 means the engine control module detected an internal processor or control fault. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0700 Code: Transmission Control System Malfunction
P0700 means the transmission control module has requested the check engine light because a transmission code is stored. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0741 Code: Torque Converter Clutch Circuit Performance or Stuck Off
P0741 means the torque converter clutch is not locking as expected. Learn the common symptoms, causes, severity, and typical repair costs.
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Knowledge Guide
P0750 Code: Shift Solenoid A Malfunction
P0750 means shift solenoid A is not operating as commanded. Learn the common symptoms, causes, severity, and typical repair costs.
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