Posted: 9/15/2007 10:07:46 PM EDT
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The "check engine" light on my 98 Ford Explorer has been turning on and off intermittently for the last year. It turns on for a few days, then turns off for a month or so, then turns back on for a few days etc. The light is always full on (never flashing). It seems like the root cause is some infrequent fault or dodgy/worn out component. The light happens to be on right now but, if the car stays true to form, the light will shut off again in a few days. This vehicle is due for an emissions test within the next month. In AZ they use the OBD to check emissions compliance. I understand that the "check engine" light being lit means I will fail the emissions test. Question: When the light turns off (which I expect it to do early next week), how long should I wait before taking the vehicle for the emissions test ? Can I take it immediately, our should I wait a while ? Even if the light has turned off, will the OBD scanner still fail the vehicle because of the stored error codes ? Should I just take the vehicle to the dealer to get whatever the problem is fixed before I take it in for testing ? |
| Take it in and get it fixed. On and educated guess since it is running ok it is most likely the egr pressure sensor Ford has a problem with them and has a updated part. On an OBD2 check if the light has been off for 3 drive cycles you should pass the test and code is just stored in history. |
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Some auto parts stores will scan the code for you. The light needs to be on for them to scan it with their cheap tester. A mechanic with a good scan tool can find stored codes. It is probably not an expensive part. If you are mechanically inclined at all, it may be an easy do-it-yourself fix. In Illinois, a lit check engine light is also cause for failure. An old code shouldn't be a problem if the repair has been done. Keep your receipt. |
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I would take it to Autozone or a mechanic friend and have them pull the codes. Could be something as stupid as a defective gas cap, I've had that code thrown several times in my Dakota. I would also reset the computer before taking it in for testing as well. I don't know how the emissions scam, err I mean testing works in AZ, but in MD if your car is post '96 (OBD II) they plug into your diagnostic port and look for stored codes. |
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Ok here is the deal. You only fail the test for an ACTIVE code. If the light is off, you pass. The computer will still print out any codes that are left in the computer for your convienience. If you ask real nice, the folks up front will even look up the codes for you. Basically Light Off = Pass |
I had a similar problem with my Duramax. The dealer had my truck for 3 days before they threw in the towel and replaced the computer ($$$$, but under warranty). I got the impression that this isn't all that uncommon, and the dealer tries all they can to fix the computer (they even re-flashed mine a couple of times) before they replace it. You should push them a bit to get them to fix it. |
Well, I took the vehicle in for its emissions test today, and it passed OK... thanks everyone for the advice. The test did also confirm the same fault code as the Autozone scanner, so I guess I'll have to get around to changing the O2 sensor sometime in the next 2 years  .
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