Check Engine Light

I recently got the check engine light on my car (Ford 2006 Taurus SE 3.0L). The weird thing is there is no shaking of the car. It starts perfectly fine, the RPM’s were the same as it was before the light went on. Then the weirdest thing is that my MPG has gone UP. Before the check engine light it was reading steady at 21.3 MPG and now it is up to 23.1. All the fluid levels are where they are supposed to be and they are on firm too (including the gas tank).

As always, get the codes read. We cannot help you without knowing the codes. You can get them read for free at most auto parts stores, like Autozone, Pep Boys, O’Reilly’s, Checkers, etc… Post the code here in the format like P0132.

I’m thinking of a slightly lean run condition that would cause symptoms you describe. The damage it can cause is burnt valves and pistons, which is a high price for slightly better gas mileage. The RPM’s and seemingly smooth running engine is the effects of your ECM trying to keep everything in tune, but the light means it is still having a problem. Getting the code read is the very first step to diagnosing the problem.

I will do that, thank-you very much.

The CEL covers a broad range of problems. Your best course of action is to find out exactly what problem is causing the CEL to come on. Take the car into an Autozone Parts store and have the codes read. At least you should gain some idea what sort of problem is likely to cause the CEL to light up.

I suspect the change in mileage is not exactly real.  Those onboard mileage readouts are estimates, based on a number of factors.  If something causes a change to one of those factors it will change the displayed mileage and there may or may not be a change in actual mileage.  In time it should recalibrate itself and be back to useful, but not real accurate mileage display.

I got some answers now for my problem with the car…

It is either

  1. Catalitic converter needs to be replaced ($91.99 + tax for a generic one)


  1. A vacuum hose needs to be replaced as it is defective.

They said to have a mechanic look at to be sure on which it is before they order a catalitic converter because they don’t want me to waste the money for it if all it needed was a hose.

About the MPG going up, they had no explanation for, but not to worry about it as I have plenty of gas in the car right now and then when the repair is done, just do a reset on it and it will get back to normal (if not just to keep an eye on the gauge for the gas situation).

I appreciate ALL the help you all have provided. I am going to get this done on Thursday (payday) and rest on Wednesday (much needed).

Did you write down the actual codes? They look like “P1234” In general you don’t want to reply on the characters at auto parts stores to give you the run down of possibilities. If you provide specific codes, folks here often know the appropriate diagnostic routines. (I.e. a lot of people here are actual mechanics).

Of course, I give whomever it was credit for saying to go to a mechanic for a proper diagnosis. It will be your best bet. But if you post codes people can even tell you whether or it seems that your mechanic knows what s/he is doing.

Not only did I write down the codes, he handed me the paper that listed what it could be. The code was P0420. He said that the mechanic would be the best to look at it for the complete and correct fixing method.

You can peruse this for a concise explanation:

When you go to a mechanic, don’t let them guess (that’s what a lot of people do). The guessing often gets very expensive and frustrating.

Any Change In Engine / Exhaust Sound ?

Some 2006 & 2007 Taurus models have had problems with separation of the exhaust flange from the catalytic converter flex coupling. A leak there can set a PO420 DTC.

Ford now makes a service kit availble for repair so that the whole converter doesn’t have to be replaced. Have the area near the flex pipe inspected while having the car looked over for the source of the problem.


Just for your information, a bad catalytic converter, one in which the inner converter ‘brick’ has a hole burnt in it, can relieve back pressure and increase gas mileage. But this seriously increases your emissions. The CEL will never go off and you’ll never pass emissions testing, if it is required in your area.

A broken or cracked vacuum line causing a leak will make the engine to run lean. This can damage pistons and valves as well as catalytic converters. A high price to pay for a little better gas mileage.

Well, here is an update to the situation. A mechanic said it was nothing to worry about as since I didn’t have any rattling of the car and the car wasn’t making loud noises. Then a day or two later the check engine light went off and has been off ever since (for over a week now). Autozone did a check and found no faults with the engine. I am perplexed but relaxing better now that I don’t have to pay over $700 for the parts and installation.

Is this also the case with 1999 Taurus? I’ve been told my LX OHV V6 is “abnormal” regarding the catalytic converter & I’d like to know if there is something that I can do to fix it other than a repair that is going to cost almost what the car is worth.