Q: Check engine, traction off lights are showing

asked by on May 13, 2016

I purchased my car used, and the check engine and traction off lights are on. I checked on the code scanner, it showed: knock sensor. After fixing that, then O2 sensor codes starting show. What else do I need to fix?

The Check Engine Light is likely still on due to the oxygen sensor faults. The unfortunate thing is that engine computers sometimes cannot detect another problem if they are dealing with one already. That may be why it didn’t have oxygen sensor faults at first, but set the faults after you fixed the other problem.

The best thing you can do now is to diagnose the issue with the oxygen sensors, as it may not be fixed by replacing the sensors. You also may need to scan the ABS control module, as there may be faults stored in that which are causing the traction control light to be on. If this sounds like more work than you are up for, I suggest contacting a professional technician to have them diagnose the real cause of the check engine light.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

stuck CD in CD player

The fact that the CD is not ejecting is an indication that the CD player is broken. The CD player will likely have to be replaced. For more information on how you may be able to do this yourself, check...

2005 Mercedes-Benz Sprinter 2500

The Check Engine light must be reset by a Scan/Clear tool that supports the Sprinter. The computer will not reset it on its own.

Check Engine codes. Need warranty for mechanic service work, any examples to ask for?

Hello there, thank you for asking about your 2001 Saab 9-3. These codes can come up if the engine needs a tune up, if it has bad coils, or even if you have dirty fuel injectors. Due to the age...

Related articles

What Does the Service Required Warning Light Mean?
The service required warning light reminds you when it's time to perform some maintenance for your car, usually an oil and filter change.
P0146 OBD-II Trouble Code: O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 3)
P0146 P0146 code definition O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 3) What the P0146 code means P0146 is the OBD-II generic code indicating the O2 sensor for bank 1 sensor 3 fails to have a voltage change...
P2784 OBD-II Trouble Code: Input/Turbine Speed Sensor A/B Correlation
P2784 means a signal from the turbine speed sensor was detected due to electrical issues, faulty sensors or solenoids or bad transmission fluid.