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Idiot light

  • 2001 Chevy Impala; 80k miles +/-

    - Check engine light – per instruction to idiot, had it checked.

    - Am informed that I have a bad catalytic converter. It won’t hurt anything, just won’t pass next (Maryland) inspection.

    - Old car, runs OK; rather than spend $700, maybe I should think about new car when inspection date rolls around.

    - Drive it for many months. Yellow light. Blinky blinky blinky.

    - Went out today. No yellow light.

    - Self-healing miracle? or bulb just tired of trying to talk to me …


We can’t tell you from a distance.
Can you park the car closer to your computer?

Seriously, however, the first thing you should do is to determine if the CEL simply burned out.
It is did, you would have no way of knowing when the next engine-related problem arises.
Then again, if the CEL is steadily illuminated, then you would also be unaware of the next big problem.

Incidentally, if the light was actually blinking for several months, I am surprised that the car is still running.
A blinking CEL indicates engine misfire, and when not corrected this can lead to damage to the catalytic converter, as well as other components.

It is very possible that your cat converter was damaged by misfiring of the engine, and that the problem still exists. These things do not cure themselves.

If the cat healed itself it’d be a first. Did a man in a beard and sandals born of a virgin recently come up and wave his hand over your hood?

Driving around with a CEL going blinky blinky is guaranteed to make you overlook it should it try to tell you a much more serious problem has developed. Have the diagnosis verified, but if you in fact need a new converter I’d recommend getting one.

If you prefer to get a new car rather than spend $700 fixing your old one, that’s a choice you can make. It won’t be an economical choice, but it’s yours to make. It’s cheaper to fix yours.

If you want to find out if the bulb burned out just turn the key to on w/out cranking. It should light up with all of the other dash lights.

Given that you have ignored giving attention to serious problems your only serious choice is probably to trade it in before inspection time.

The whole thing about “idiot” lights was that you’d have to be an idiot to - let’s say not check your oil regularly and wait for the light to tell you about it after its too late.

For the check engine light the idiotic part comes when it is ignored. So the logic has kind of reversed. The computer controls and monitors the engine’s performance. When something is out of spec it stores an error code and turns on the light to tell you the error code is there. Paying attention to it is just one of the things you need to do to take care of your car these days.

I lied. It wasn’t really blinking; that was poetic license, but it sure was bright. And constant. I actually had two identical bad-catalytic diagnoses - the first time, they just turned it off, and advised me of the options. The second time, after 60 days or so, it popped back on, with same analytic result.

Checking blue book, In good shape, I could sell it for about $4k, minus the fix; or trade it in for about $2k, same subtraction. I figure with the light now out, I could donate it to the NPR radio station for full value tax write-off, and blame any repercussions on Tom and Ray

Follow-up – it’s not the bulb. Thanks for the suggestion – it test-lights OK. Which takes us back to the original question. Why would it NOT light if the converter is still bad. I’m told there are two sensors, in-and-out, the difference between their readings being what’s measured to determine an ineffective converter. Maybe I’m seeing a partial answer? . Would 2 faulty sensors “cancel” each other?

The system will test the converter only under certain conditions, typically engine fully warmed up and cruising at a steady 40-60mph. If the converter is marginal a few good tests in a row will turn the light off. A bad converter at 80K means something else isn’t right and a replacement converter will likely have a short life too.

A check engine light sets codes. None of those codes tell you that a catalytic converter is bad. If you really want advice see if you can find out what the actual codes were - format: P1234.

Understood - both bad-converter analyses were provided by my local shop that does all my maintenance - they read the codes the same, each time, with their dandy meter, for $68.24. It doesn’t say HOW bad, only that the sensors are telling us it wouldn’t meet inspection emission standards. Having said that, with the light now strangely dark, without me doing anything at all to it, I don’t know what it is(n’t) telling me. I gather it’s even unlikely but possible I could have a good converter and bad sensors. CarTalk search shows converters available for well under $300, plus labor, but I’m guessing a 10 year old car may have other issues lurking. Decision time.

You don’t have to pay $70.00 to get your codes scanned.
Any national chain parts retailer-Autozone, O’reilly, etc, etc…will do it for FREE.

A good tech can look at the upstream and downstream sensor signals on a scope and tell if the converter or a sensor s bad.

The attached link isn’t quite as demonstartive as what I was looking for, but youu’ll get the idea.

Welcome back little yellow light. Yup; it lit back up after two days of darkness. The Chevy Gods have a perverse sense of humor, and are testing my commitment to finding the truth.

You still need to post code(s) - see posts re: free scanning at auto parts stores above