I have a great running 1997 Honda Civic HX that has an issue with the check engine light coming on at random times. I have taken to the dealer and all they are able to do is clear the codes. Not able to read or diagnose. Connection error comes up on the OBDII diagnostics.
I have noticed no real pattern in when the light comes on but possibly when I have a hard acceleration or a sudden decceleration but the car makes not change in sound, no decrease in acceleration. No real sign of any engine problem or problem at all. Seems to me more of a connection issue with sensors and the computer on the vehicle. I still average 35-40mpg so I'm happy. Just worried about passing emmissions with the Check Engine Light on. Any advice would be much appreciated.

Thanks

I doubt it has anything to do with emissions. I don't think they check emissions with the car computer. I know they hook the emissions up to their computer.
My guess is you are right there may be a short or something in the computer wiring.

The next time the CEL comes on, take it to AutoZone, or buy your own scanner/code reader. There has to be a code stored in memory, when the CEL comes on. Possibililities may include oxygen sensor, ICM, and coil. Go over the entire electrical system, focusing on spark plugs (NGK only), wires, distributor cap, rotor, ICM, and coil. Ensure none of them are too old.

The situation is I'm in Illinois and new emission practice is to ensure there are no codes on your vehicle. Additionally, the problem is when you hook up a code reader it only reads errors so there are no issues that can be addressed at that point. I'm wondering if anyone has ever experience such a problem. Maybe a lose harness or connection that gives way on Honda's?

You might want to check the catalytic converter, I have a same problem with my 99 honda civic 3 years ago, and no body can tell what was going on. And the same thing only thing they can do is to reset the code to turned the engine light off. It failed on new emission test but it pass on old passion emission test. So the computer is sending a wrong signal. But the fix is the crack catalytic converter, I replaced the cat and everything back to normal and it pass on both emission test.

Klug,
I have the same car and the same problem. Have had both for years. I'm coming up to 220k miles, still get great gas mileage. My husband used to be an auto mechanic, knows engines inside-out. He did everything he could, and then some, but this problem persists. I really want to make it to 250k miles, but I am due for an emissions test and not sure I can pass this time. Have you had any luck since you posted this?

MelonLord, were any codes thrown? What has your husband tried, to rectify the problem?

Eek, I don't remember the answers to that, I'll have to ask him and get back to you. I know that it was (is) a problem with sensor and not the engine. The car runs great - always has.

Great.

We did get codes, my husband cleaned/replaced the things the codes pointed to (such as EGR - he replaced valve) but the problem persists. He said the thresholds are set too low. There was a certificate issued from Honda that stated this, up to 160k miles. I had 162k miles at the time.

Any current codes?

What thresholds are set too low?

It's too hot now to resume the cat and mouse game of code-chasing. When it cools off enough my husband will get the latest and greatest set of codes - none of which were able to settle the engine light when addressed in the past. I'm hoping in the meantime that someone who's had this problem can tell me what their resolution was.

Good luck. You'll be waiting a long time.

Reset and passed emissions!

I'm happy for you, but that response is not very informative to others.

I have a 97 HX 359,200 all orig. miles only problem I've had is egr ports pluged up I clean them every 100kmi,44-50 mpg 5sp still orig.clutch. You have to pull the fuel inj.rail to access the cover for the egr ports,not too hard to do.they plug up and cause misfire,bad gas milage.I get all my main Honda parts from Majestic honda.com 30% off.I do most of work on my car, full syn oil(valvoline).The only thing they missed is putting cruise control on the car,they waited till 02-03.(mike w.)[email protected]