Top 10 Honda Accord DTC Diagnostic Trouble Codes
Discover the top 10 most common diagnostic trouble codes for Honda Accord, including their causes, symptoms, and solutions. Learn how to fix issues like catalytic converter efficiency, misfires, EGR flow problems, and more, and keep your Accord running smoothly.
TOP 10 DTCS
DTC P0420: Catalyst System Efficiency Below Threshold (Bank 1)
Description: The catalytic converter is not working as efficiently as it should, leading to increased emissions.
Cause: A faulty catalytic converter or oxygen sensors located in the exhaust
system.
Symptoms: The Check Engine Light (CEL) is illuminated. The vehicle’s performance may decrease, its fuel economy may decrease, and there may be a decrease in power or acceleration.
Solution: Replace the catalytic converter or oxygen sensors.
DTC P1259: VTEC System Malfunction
Description: The Variable Valve Timing and Lift Electronic Control (VTEC) system is not working properly.
Cause: Faulty VTEC solenoid or oil pressure issues located in the engine
Symptoms: The Check Engine Light (CEL) is illuminated. The engine may run rough or stall, and there may be a decrease in power or acceleration.
Solution: Repair or replace the VTEC solenoid or fix oil pressure issues.
DTC P0300: Random or Multiple Cylinder Misfire Detected
Description: Multiple cylinders are not firing properly, leading to a rough-running engine and decreased performance.
Cause: Faulty spark plugs, ignition coils, fuel injectors, or vacuum leaks located in the engine
Symptoms: The Check Engine Light (CEL) is illuminated. The engine may run rough, vibrate, or stall, and there may be a decrease in power or acceleration.
Solution: Replace the faulty component causing the misfire.
DTC P0301: Cylinder 1 Misfire Detected
Description: Cylinder 1 is not firing properly, leading to a rough-running engine and decreased performance.
Cause: Faulty spark plugs, ignition coils, fuel injectors, or vacuum leaks located in the engine
Symptoms: The Check Engine Light (CEL) is illuminated. The engine may run rough, vibrate, or stall, and there may be a decrease in power or acceleration.
Solution: Replace the faulty component causing the misfire in cylinder 1.
DTC P1456: Evaporative Emissions Control System Leakage (Fuel Tank System)
Description: The Evaporative Emissions Control (EVAP) system is not sealing properly, leading to fuel vapors escaping from the fuel tank.
Cause: A faulty gas cap, leaky fuel lines, or a faulty EVAP canister located in the fuel tank
system.
Symptoms: The Check Engine Light (CEL) is illuminated. There may be no noticeable symptoms at first, but over time the vehicle’s performance may decrease, its fuel economy may decrease, and there may be a decrease in power or acceleration.
Solution: Repair or replace the faulty component causing the fuel tank system leak.
DTC P0171: System Too Lean (Bank 1).
Description: The air/fuel mixture is too lean, meaning there is not enough fuel being burned with the air in the engine.
Cause: a faulty oxygen sensor, a vacuum leak, or a clogged fuel filter located in the engine.
Symptoms: The Check Engine Light (CEL) is illuminated. The engine may run rough, vibrate, or stall, and there may be a decrease in power or acceleration.
Solution: Replace the faulty component causing the lean air/fuel mixture.
DTC P0740: Torque Converter Clutch Circuit Malfunction
Description: There is an issue with the torque converter clutch circuit, which engages the engine with the transmission.
Cause: Faulty torque converter clutch solenoid, damaged wiring, or low transmission fluid located in the transmission.
Symptoms: The Check Engine Light (CEL) is illuminated. The engine may stall or hesitate when shifting gears, and there may be a decrease in power or acceleration.
Solution: Repair or replace the faulty component causing the torque converter clutch circuit to malfunction.
DTC P0135: O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1).
Description: The O2 sensor’s heating element is not functioning correctly.
Cause: A faulty O2 sensor, damaged wiring, or blown fuse located in the engine.
Symptoms: The Check Engine Light (CEL) is illuminated. There may be no noticeable symptoms at first, but over time the vehicle’s performance may decrease, its fuel economy may decrease, and there may be a decrease in power or acceleration.
Solution: Repair or replace the faulty component causing the O2 sensor heater circuit to malfunction.
DTC P0302: Cylinder 2 Misfire Detected
Description: Cylinder 2 is not firing properly, leading to a rough-running engine and decreased performance.
Cause: Faulty spark plugs, ignition coils, fuel injectors, or vacuum leaks located in the engine
Symptoms: The Check Engine Light (CEL) is illuminated. The engine may run rough, vibrate, or stall, and there may be a decrease in power or acceleration.
Solution: Replace the faulty component causing the misfire in cylinder 2.
DTC P0401: Exhaust Gas Recirculation (EGR) Flow Insufficiently Detected
Description: The EGR valve is not allowing enough exhaust gas to recirculate back into the engine, leading to increased emissions.
Cause: a clogged EGR valve, damaged wiring, or a faulty EGR valve located in the engine.
Symptoms: The Check Engine Light (CEL) is illuminated. There may be no noticeable symptoms at first, but over time the vehicle’s performance may decrease, its fuel economy may decrease, and there may be a decrease in power or acceleration.
Solution: Clean or replace the EGR valve, or repair the wiring, or replace the faulty EGR valve.
Keeping your Honda Accord running smoothly requires understanding common diagnostic trouble codes and how to fix them. By addressing issues like misfires, EGR flow problems, and catalytic converter efficiency, you can improve your vehicle’s performance, fuel economy, and overall reliability. With the right knowledge and expert tips, you can keep your Honda Accord in top shape for years to come.