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2001 Passat Engine Warning Light

Hello.

The 2001 Passat 1.8lT has an engine warning light on and feels like it is running on less than all four cylinders.( very rough idle) This is the first time we have seen this particular warning light and the manual suggests that it has a problem with the catalytic convertor.( 170K miles on the car) The car had no symptoms until the light came on today and the car was serviced last week. ( oil change and new tires) It seems that every time I take the car in for service something goes haywire shortly afterward. Does anyone have an idea how much this repair might cost? Also, is this something that can result from mechanic foul play?

Thank you

The cat function is often determined in part by the ECM measuring the O2 sensors. There may also be a cat temp sensor. If the shop accidentally damaged the connections or the sensors, that could indeed be the cause of the light coming on. And a damaged O2 sensor or connection could be the cause of the engine performance problem you are noting.

Probably the first step is a visual on the O2 and cat sensors.

It’s entirely possible – and probably this is what is most likely – you simply need a new cat; i.e. it has nothing to do with the oil change and tires. Not that unusual in a 2001 with 170K. Esp if you are on the original cat.

That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here.

Hello again,
I took the car to a different repair shop than I have used before and was happy with the result.
One of the engine coils was bad so it really was firing on three cylinders. Here is the question - the operators manual said it was okay to keep driving with this particular warning light on so it was driven for about 35 miles to get it home. The mechanic today made a passing reference to the gas spray for this coil getting into the catalytic convertor while it was being driven. Is this going to kill the catalytic convertor or can it take a bit of unintended abuse?

Thanks again

Is this going to kill the catalytic convertor or can it take a bit of unintended abuse?

It depends on how much abuse.

That said, I still suggest having that CEL read and with the results known you will be in a better condition to determine if you are going to cause damage due to possible use.

The shop fixed the coil problem yesterday. The car is no longer giving a CEL. How long does the car hold the old codes or are they cleared with the repair?

Thanks again.

Even if the code/s were cleared. The computer is still going to iether look for a predetermined amount of drive cycles to be completed or a certain amount of mileage without any faults.

After that point, if the computer see’s that everything tested and ran within parameters then you can go for an emmissions test.