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Pontiac Grand Prix 2007 - Transmission codes

Hi there,

So my check engine light came on today and my car started making this metal grinding/whining sound. I took it to a mechanic that ran the codes. Alot of codes came up, including these 2 discerning ones: p0116 and p1811. What they are telling is that something is stuck in the exhaust and if they can get it out/fix it, it may help with these discerning codes. They are also telling me that since I recently had some battery problems and needed to get the alternator replaced, that could also be the reason these codes are coming up. I guess what I’m asking is, could either of these explanations be the case…or is my transmission just fried and I should cut my losses. I am concerned that I am being gouged for money to fix things that wont make a difference with the main problem at the end of the day.

What leads you to believe you have a transmission problem?

Try replacing the coolant temp sensor for the computer.

And that may get rid of the P1811 code.


Because I was told what those codes mean?

Does that work sometimes?

I would also ask how many miles are on this car, and at what mileage was the transmission fluid drained and replaced?

When the code P0116 appears, unless you have a scanner that allows real-time monitoring of the sensors, the coolant temp sensor is replaced.

The coolant temp sensor is one of the primary inputs into the computer. And if this sensor is providing an erroneous signal, the computer won’t know how the engine/transmission should operate.


230,000 km and i just had the transmission fluid exchanged about a week ago

The P1811 is a transmission code but it may be driven by the P0116 code. As Tester said, fix that and the P1811 may go away.

The metallic whining noise does not seem to indicate something stuck in the exhaust. You have not provided enough info to understand that. If there were other codes, might help to let us know what those were as well as better description of the noise.

You have 143,000 miles on an over 10 year old car. It’s well past it’s “freshness date”. I’d start preparing to replace it soon. But, try what @Tester said first. It’s sound advice and not expensive.

When you had the transmission fluid changed, was the filter also changed? If not, a clogged filter could cause a whining noise.

Ok thanks guys! I appreciate the information you’ve given me

Perhaps I’m missing something, but the two codes don’t indicate to me that there’s any exhaust problem involved. Is there a reason why your shop thinks that? Sometimes external exhaust parts (like the heat shields, hangers) can get loose and that will cause weird noises, maybe that?

Don’t make any funeral arrangements. Its a Grand Prix with the venerable 3800 V-6! It’s just getting broken-in.

I own 3 GM cars with the 3800 engine, 2 are Pontiacs and 1 of those is a Grand Prix.

My old Impala has over 300,000 miles and my Bonneville has 178,000. The Grand Prix is lower miles. They’re all still going strong.

I like driving the Grand Prix so much I hope I never have to get rid of it.

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