Honda Diagnostic Trouble Codes
OBD2 fault codes seen on Honda vehicles, with what each code means, its typical repair cost range, and notes on specific Honda models.
Electrical
Intake Camshaft Position - Timing Over-Retarded (Bank 1)
Honda Civic 1.8L R18 / 2.0L K20 • 2006-2015
R18A and K20Z engines use a VTC actuator on the intake cam. The cold-start grinding rattle usually p...
Throttle Position Sensor/Switch A Circuit Range/Performance Problem
Honda Civic • 2006-2015 (R18A1 1.8L, K24Z 2.4L Si)
On these Civics P0121 often points to the accelerator pedal position sensor or chafed wiring at the ...
Throttle/Pedal Position Sensor/Switch A Circuit Low Input
Honda Civic • 2006-2015 (R18A 1.8L, 8th and 9th gen)
Uncommon on the Civic, but when it appears the throttle body assembly is the usual culprit. After an...
Throttle/Pedal Position Sensor/Switch A Circuit High Input
Honda Civic • 2006-2015
8th/9th gen R18 engines occasionally log P0123 after aftermarket intake installs that disturb the th...
Engine Overspeed Condition
Honda Civic • 2006-2024
P0219 on Honda Civic is almost always driver-caused: an accidental downshift (from 4th to 2nd instea...
Knock Sensor 1 Circuit Malfunction (Bank 1 or Single Sensor)
Honda Civic • 2006-2015
R18A1 (1.8L) and K20/K24 engines. The sensor bolts to the back of the block below the intake manifol...
Idle Air Control System Circuit Low
Honda Civic • 2001-2011
Honda Civics with the K20 use an idle air control valve that is generally reliable but can suffer wi...
Idle Air Control System Circuit High
Honda Civic • 2001-2011
The R18A Civic is drive-by-wire and has no separate idle air control valve, so a genuine P0509 on on...
Emissions
Camshaft Position B - Timing Over-Advanced or System Performance (Bank 1)
Honda Civic • 2006-2024
Honda uses VTC (Variable Timing Control) on the exhaust or intake cam depending on engine. On the R-...
O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)
Honda Civic • 2006-2024
The R18A in older Civics can set P0131 from an ageing upstream sensor on a high-mileage car. The 1.5...
Oxygen Sensor Circuit No Activity Detected (Bank 1, Sensor 1)
Honda Civic • 2001-2015
K20 and R18 engines can log P0134 when the O2 sensor heater fuse in the underhood box blows or the P...
O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)
Honda Civic • 2006-2024
The upstream sensor on the R18A is accessible from the top of the engine, making it one of the easie...
O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)
Honda Civic • 2006-2024
Honda Civics use NTK/NGK sensors as OEM. The downstream sensor on the R18A is straightforward to acc...
Catalyst System Efficiency Below Threshold (Bank 1)
Honda Civic • 2006-2024
On 2006-2011 Civics with the R18A engine, P0420 is frequently caused by a tired rear oxygen sensor r...
Intake Air System Leak
Honda Civic 1.8L R18A • 2006-2011
R18 owners commonly find the PCV hose to the intake manifold hardens and cracks at the fitting. The ...
Ignition
Crankshaft Position - Camshaft Position Correlation (Bank 1 Sensor A)
Honda Civic • 2006-2024
The 1.5T (L15B7) in 2016+ Civics uses a VTC actuator that can fail, causing P0016 alongside a loud r...
Camshaft Position Sensor Circuit Malfunction
Honda Civic • 2006-2024
The Honda Civic CMP sensor on the R18A is a simple two-wire magnetic pickup, while the 1.5T uses a t...
Ignition Coil A Primary/Secondary Circuit Malfunction
Honda Civic • 2006-2015
R18A1 1.8L often throws P0351 from a corroded connector rather than a bad coil. Check the coil conne...
Ignition Coil B Primary/Secondary Circuit Malfunction
Honda Civic (8th/9th gen) • 2006-2015
R18 1.8L SOHC has a durable coil-on-plug setup. When P0352 shows up here it's more often the plug or...
Ignition Coil C Primary/Secondary Circuit Malfunction
Honda Civic • 2006-2015 (R18 1.8L, K24 2.4L Si)
Honda coil-on-plug units are reliable. When they do fail, it's usually because a leaking valve cover...
Ignition Coil D Primary/Secondary Circuit Malfunction
Honda Civic • 2006-2015
R18A1 (1.8L) and K24Z7 (Si 2.4L) rarely fail coils outright. Check the coil sub-harness where it run...
Fuel System
Mass Air Flow Sensor Range/Performance
Honda Civic • 2006-2024
Honda uses a Keihin MAF integrated into the airbox on many Civic models. The 1.5T (2016+) is more se...
System Too Lean (Bank 1)
Honda Civic • 2006-2024
The naturally aspirated R18A in older Civics can develop leaking intake manifold seals that let in u...
System Too Rich (Bank 1)
Honda Civic • 2006-2024
The 1.5L turbo in 2016+ Civics has a documented fuel-dilution issue where gasoline thins the engine ...
System Too Lean (Bank 2)
Honda Civic • 2006-2024
Nearly every Civic is an inline-four with a single bank, so it sets P0171 rather than P0174. If a sc...
Idle Air Control System RPM Lower Than Expected
Honda Civic • 2006-2015
The eighth-generation Civic with the R18A uses a drive-by-wire electronic throttle body, so there is...
Idle Air Control System RPM Higher Than Expected
Honda Civic • 2006-2024
The eighth-generation Civic with the R18A uses a drive-by-wire electronic throttle body, so there is...
Cooling System
Coolant Thermostat Below Regulating Temperature
Honda Civic • 2006-2024
Honda thermostats open at 76 to 80C depending on the model year, and the R18A unit is easy to reach....
Cooling Fan 1 Control Circuit Malfunction
Honda Civic • 2006-2015
8th and 9th gen Civics with the R18 rarely throw P0480 early in life. When they do at high mileage, ...
Misfire
EVAP System
Evaporative Emission System Vent Control Circuit
Honda Civic • 2006-2024
Honda Civics have the EVAP vent valve integrated near the fuel tank. Access may require partial remo...
Evaporative Emission System: Very Small Leak
Honda Civic • 2006-2024
P0456 on a Civic is often a fuel cap issue or a cracked vapour line near the rear axle. On the 2016+...
Transmission
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