I have an MR2 Spyder with 80,000 miles on it runs great but the check engine light is on and the smog technician stated that even if I reset the check engine light it would still not pass smog no matter what the reason for the check engine light being on is that true?

2 Answers 2


What the technician told you is exactly right.

OBD2 cars have their emissions measured (at least in most states) by the readings of the computer in the car (OBD1 cars still must use tail pipe readings). The OBD2 system does what's called a drive cycle. Every manufacturer has their own drive cycle. The drive cycle eliminates (IIRC) eight different things it checks for having to do with emissions. When you reset the computer (erase all of the codes - for whatever reason) and reset the CEL light (goes dark), you still have to put the car through its drive cycle. If you don't, it's still in limbo and will not pass the test. If you have an emissions related issue, resetting the computer and going through the drive cycle will only cause the issue to reappear as a CEL.

The tech was also correct in that if the CEL is on for any reason, it's an automatic failure. Even if it's an innocuous code (nothing to do with emissions), you still fail.


Most smog tests are done by measuring the exhaust emissions using a sensor in the tailpipe, so resetting the light will make no difference - you need to sort out the emissions to make sure they are below the limit for your jurisdiction. You should get the codes read to find out why the CEL was on, and fix the problem that caused it.

If you edit your question to state which country (and state, if applicable) you are in, some of our members may be able to help more.

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