Skip the auto shop - Our mechanics make house calls

Q: Can't pass smog check with Check Engine Light on

asked by on

The Check Engine Light keeps coming on, preventing me from passing a smog check. I replaced the compression sensor already.

A: The most common reason for your Check Engin...

The most common reason for your Check Engine Light coming on is for random engine misfires. You may be having this problem, and may need to have the ignition diagnosed, to see what is causing the misfire. You may have a failure of your coils, or plugs. The Check Engine Light would need to be checked to see which codes are received, for a proper diagnosis.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

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

Q: Turbo leaks oil

Hello. Dye needs to be placed in the engine oil to determine if it’s the turbo or something else leaking around the turbo. I would recommend having a certified mechanic locate and repair the leak to have this problem taken...

Q: Has a rough idle with no CEL on

I would try and have the fuel injectors and throttle body cleaned out. This should clean out injectors and intake valve carbon deposits that can cause the rough idle. If after driving the vehicle, and the CEL comes on, then...

Q: Can leaks in the valve cover gasket affect the performance and power of a VW Touareg V8?

Hi, thanks for writing in. The answer is yes. The oil getting on the spark plug wires and plugs will cause the engine to misfire. The valve cover gaskets will need to be replaced along with plugs. The wires will...

Related articles

P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.