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Car Trouble Codes by Make: OBD-II Check Engine Code Guides

A check engine light is a message, not a verdict. This page collects every trouble code guide on NextCarReview, grouped by make, so you can go from the code on your scanner to the likely causes, the cheapest things to check first, and a realistic idea of repair cost. Start with the make section if your code begins with P1, because those are manufacturer specific. Start with the generic section if it begins with P0 or U0.

Compiled by Morgan Reyes
This page is a directory of our published guides on this topic. It is updated as new guides go live.

Featured guides

P1148 Nissan Code: Causes, Symptoms, Diagnosis, and Repair Cost Guide 2026P1148 means the closed loop control function did not operate on Bank 1.
P0300 Code: What It Means, Symptoms, Cheapest-First Causes, and 2026 Repair Cost GuideWhat it covers: What It Means, Symptoms, Cheapest-First Causes, and 2026 Repair Cost Guide.
P0420 Code Explained: Causes, Fixes, and 2026 Repair CostsWhat it covers: Causes, Fixes, and 2026 Repair Costs.
Keep Your Car Happy: The Simple Guide to All Types of Car MaintenanceThis guide breaks down all the types of car maintenance, from simple checks to big services.

How to read an OBD-II trouble code

Every gasoline car and light truck sold in the United States since the 1996 model year has an OBD-II port, usually under the dashboard near the steering column. When the engine computer sees a reading outside the range it expects, it stores a diagnostic trouble code (DTC) and, for emissions related faults, turns on the check engine light. A basic scan tool or a free code read at a parts store will pull that code in a minute or two.

The code itself follows a simple pattern. The first letter tells you the system: P for powertrain (engine and transmission), B for body, C for chassis and U for network communication between modules. The first digit tells you who defined it. A 0 means the code is a generic SAE code that means the same thing on a Ford as on a Toyota. A 1 means the manufacturer defined it, so a P1148 on a Nissan has nothing to do with a P1148 on another brand. That is why this hub separates make specific guides from generic ones.

What to do in the first ten minutes

Before you order parts, write down every code that is stored, not just the first one. Codes often travel in groups, and the pattern matters. A lean code alongside a misfire code points somewhere different than a lone misfire. Note the freeze frame data if your scanner shows it, since it records engine speed, temperature and load at the moment the fault was set.

Next, look at how the light is behaving. A steady check engine light means the car has logged a fault and you should get it checked soon. A flashing light usually means an active misfire severe enough to damage the catalytic converter, and the safe move is to reduce load and stop driving as soon as you safely can. If the light comes with overheating, oil pressure warnings, a loss of power or strange noises, treat it as urgent regardless of the code.

Then check the free things. A loose or worn gas cap is a classic cause of EVAP codes. Low oil can trigger cam timing codes on engines with variable valve timing. A battery that is weak or has corroded terminals can set a string of communication codes that disappear once voltage is stable. Our guides list causes in cheapest first order for exactly this reason.

Generic codes versus make specific codes

Generic P0 codes such as P0300 (random misfire), P0420 (catalyst efficiency) or P0171 (system too lean) describe a symptom, not a failed part. The same code can come from a spark plug, a vacuum leak, a sensor or a software issue. The generic guides below explain the common causes across brands and how to narrow them down.

Make specific guides go further. They cover the engines and model years where a code tends to show up, the service bulletins and recalls that the manufacturer has published, and whether an extended warranty may cover the repair. If your car is still under a powertrain warranty or an emissions warranty, check that before paying for a repair out of pocket, because some emissions parts carry longer federal coverage than the basic warranty.

Clearing codes and passing inspection

Clearing a code with a scanner turns the light off, but it does not fix anything, and it resets the readiness monitors that emissions inspection stations check. If you clear codes the day before a state inspection, the car will likely fail for monitors that are not ready. Drive a normal mix of city and highway miles over a few days so the monitors can run, then confirm with a scan tool that they report ready before you go.

When to take it to a shop

DIY diagnosis makes sense for sensors, plugs, coils, gas caps and vacuum hoses on most cars. It makes less sense for internal engine faults, transmission problems, high voltage hybrid systems, and anything that requires the dealer scan tool to relearn or program a module. When you do go to a shop, bring the codes and the freeze frame data. A good technician will confirm the fault with testing rather than replacing parts based on the code alone, and you can ask for the test results in writing.

Repair cost ranges in our guides are there to help you recognize a fair quote. Your actual price depends on your region, labor rates, parts brand and the exact engine in your car, so get a written estimate before approving work.

All guides in this section

Nissan codes

Ford codes

Toyota codes and fixes

Honda fixes

Hyundai and Kia codes and fixes

Other makes

Generic P0 and U0 codes (all makes)

Maintenance basics that prevent codes

Chevrolet codes

Honda codes

Jeep codes

More Nissan codes

More Ford codes

Frequently Asked Questions

What does a P1 code mean compared to a P0 code?
A P0 code is a generic SAE code that means the same thing on every make. A P1 code is defined by the manufacturer, so its meaning depends on the brand. Always look up P1 codes in a make specific guide.
Is it safe to drive with the check engine light on?
A steady light usually means you can drive carefully to get the car checked soon. A flashing light usually signals a severe misfire, so reduce load and stop as soon as it is safe to avoid damaging the catalytic converter.
Will disconnecting the battery clear a trouble code?
It may turn the light off on many cars, but it does not fix the fault and it resets the readiness monitors. If the problem is still there, the code will return, and the car may fail an emissions inspection until the monitors run again.
Where can I get my trouble code read for free?
Many large auto parts chains in the US will read codes at no charge. You can also buy an inexpensive OBD-II scanner or Bluetooth adapter that works with a phone app.
Are P1148 codes only on Nissans?
P1148 is a manufacturer specific code, so its meaning on a Nissan (closed loop control, bank 1) applies to Nissan. Our two P1148 guides cover the Nissan meaning in detail.