Check engine codes
Plain-English meanings and prices
Type in the code from your scanner or the parts store to see what it means and whether it’s OK to drive. If it’s a job we do, our price is right there too.
Common codes
P0420
OK to driveCatalyst System Efficiency Below Threshold (Bank 1)
The catalytic converter on bank 1 isn't cleaning the exhaust as well as it should.
Common causes
- Worn-out catalytic converter
- Faulty downstream oxygen sensor
- Exhaust leak
- Misfires or oil burning that damaged the converter
Don't buy a converter on the code alone. We check the sensors and look for leaks first. A converter itself is quoted after the look-over.
What we’d do · flat labor
How to read a code
Every code is five characters. The letter is the system: P powertrain (engine and transmission), B body, C chassis, U network. The first number tells you who defined it: 0 or 2 means generic, the same on every car; 1 means the carmaker defined it. The next digit is the subsystem, like 3 for ignition and misfires or 4 for emissions.
A code isn’t a diagnosis
A code tells us which system noticed a problem. It doesn’t say which part failed. A lean code can be a vacuum leak, a dirty sensor or a weak fuel pump, so our $75 diagnostic tests before anyone buys parts. It comes off the repair if we do the work.
Flashing light?
A flashing check engine light means an active misfire. Drive as little as possible and text us.
Code list
74 common codes, explained
| Code | What it means | Drive? |
|---|---|---|
| P0010 | The computer sees a problem in the circuit that controls intake cam timing. | Book soon |
| P0011 | Intake cam timing isn't where the computer told it to be. | Book soon |
| P0014 | Exhaust cam timing isn't where the computer told it to be. | Book soon |
| P0016 | The crank and cam sensors disagree about engine timing. | Book soon |
| P0087 | The fuel system can't hold the pressure the engine needs. | Book soon |
| P0101 | The airflow sensor's reading doesn't match how the engine is running. | OK to drive |
| P0102 | The airflow sensor signal is lower than it should be. | OK to drive |
| P0113 | The intake air temperature sensor reads open or out of range high. | OK to drive |
| P0117 | The coolant temperature signal is shorted low, so the computer thinks the engine is extremely hot. | Book soon |
| P0118 | The coolant temperature signal is open or high, so the computer thinks the engine is very cold. | Book soon |
| P0122 | The throttle position signal is lower than possible. | Book soon |
| P0128 | The engine takes too long to warm up, usually because the thermostat is stuck open. | OK to drive |
| P0130 | The upstream oxygen sensor's signal isn't behaving right. | OK to drive |
| P0133 | The upstream oxygen sensor reacts too slowly. | OK to drive |
| P0135 | The heater inside the upstream oxygen sensor isn't working. | OK to drive |
| P0141 | The heater inside the downstream oxygen sensor, after the catalytic converter, isn't working. | OK to drive |
| P0171 | The engine is getting too much air or not enough fuel on bank 1. | Book soon |
| P0172 | The engine is getting too much fuel or not enough air on bank 1. | Book soon |
| P0174 | The engine is getting too much air or not enough fuel on bank 2. | Book soon |
| P0175 | The engine is getting too much fuel or not enough air on bank 2. | Book soon |
| P0217 | The engine has overheated. | Stop driving |
| P0299 | The turbo isn't making the boost the computer expects. | Book soon |
| P0300 | More than one cylinder is misfiring, or the misfire moves around. | Book soon |
| P0301 | Cylinder 1 is misfiring. | Book soon |
| P0302 | Cylinder 2 is misfiring. | Book soon |
| P0303 | Cylinder 3 is misfiring. | Book soon |
| P0304 | Cylinder 4 is misfiring. | Book soon |
| P0305 | Cylinder 5 is misfiring. | Book soon |
| P0306 | Cylinder 6 is misfiring. | Book soon |
| P0307 | Cylinder 7 is misfiring. | Book soon |
| P0308 | Cylinder 8 is misfiring. | Book soon |
| P0309 | Cylinder 9 is misfiring. | Book soon |
| P0310 | Cylinder 10 is misfiring. | Book soon |
| P0311 | Cylinder 11 is misfiring. | Book soon |
| P0312 | Cylinder 12 is misfiring. | Book soon |
| P0325 | The computer sees a problem in the knock sensor circuit. | OK to drive |
| P0335 | The computer isn't getting a good signal from the crankshaft position sensor. | Stop driving |
| P0340 | The computer isn't getting a good signal from the cam position sensor. | Book soon |
| P0401 | Not enough exhaust gas is flowing through the EGR system. | OK to drive |
| P0402 | Too much exhaust gas is flowing back into the intake. | Book soon |
| P0411 | The secondary air system, used at cold start, isn't moving enough air. | OK to drive |
| P0420 | The catalytic converter on bank 1 isn't cleaning the exhaust as well as it should. | OK to drive |
| P0430 | The catalytic converter on bank 2 isn't cleaning the exhaust as well as it should. | OK to drive |
| P0440 | A general fault in the fuel vapor (EVAP) system. | OK to drive |
| P0441 | The EVAP system isn't purging fuel vapor the way it should. | OK to drive |
| P0442 | A small leak in the fuel vapor system. | OK to drive |
| P0446 | A problem with the valve that vents the fuel vapor system. | OK to drive |
| P0455 | A large leak in the fuel vapor system. | OK to drive |
| P0456 | A very small leak in the fuel vapor system. | OK to drive |
| P0457 | The computer thinks the gas cap is loose or missing. | OK to drive |
| P0496 | Fuel vapor is being purged when it shouldn't be. | OK to drive |
| P0500 | The computer isn't getting a vehicle speed signal. | Book soon |
| P0505 | The idle control system can't hold the target idle speed. | OK to drive |
| P0506 | The idle is lower than the computer wants. | OK to drive |
| P0507 | The idle is higher than the computer wants. | OK to drive |
| P0521 | The oil pressure reading doesn't make sense. | Stop driving |
| P0562 | The computer sees low system voltage. | Book soon |
| P0563 | The computer sees system voltage that's too high. | Book soon |
| P0571 | The brake pedal switch signal is out of range. | Book soon |
| P0600 | Control modules are having trouble talking to each other. | Book soon |
| P0606 | The engine computer has detected an internal fault. | Book soon |
| P0700 | The transmission computer stored its own fault and asked for the check engine light. | Book soon |
| P0715 | The transmission input speed signal is missing or wrong. | Book soon |
| P0720 | The transmission output speed signal is missing or wrong. | Book soon |
| P0730 | The transmission is slipping or isn't in the gear it should be. | Stop driving |
| P0740 | The torque converter lockup circuit has a fault. | Book soon |
| P0741 | The torque converter isn't locking up when it should. | Book soon |
| P0750 | A transmission shift solenoid has a fault. | Book soon |
| P2096 | The sensor after the converter sees a lean mixture. | OK to drive |
| P2097 | The sensor after the converter sees a rich mixture. | OK to drive |
| P2135 | The two throttle position signals disagree. | Stop driving |
| P2187 | The engine runs lean at idle on bank 1. | OK to drive |
| P2195 | The upstream oxygen sensor reads lean and stays there. | OK to drive |
| U0100 | Other modules can't talk to the engine computer. | Stop driving |
Text us what the car is doing. We’ll send a price.
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