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clueless 97 deVille owner


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I own a 97 DeVille that I love!! LUX and such a nice ride!! This car rides great and I have never had any trouble with the tranny. The "check engine soon" light came on and I took it in to the dealer... They tell me I need a new transmission!!! The codes they gave me on the paperwork were PO741, PO742 and PO404.

Can someone who knows this stuff please advise me... If it's an EGR valve or a TCC (?) could I possibly fix the problem with a transmission flush or do I really need to replace the whole tranny ( to the tune of thousands of $$$$$)

Thanks in advance for any advise.

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First let's verify those codes by accessing the codes yourself. At this link: http://www.caddyinfo.com/readingcodes.html you'll find directions on how to access them.

For your 97 Deville it's:

1. Turn the ignition switch ON. [bruce notes: interestingly, the engine can be on or off]

2. On the cars up to 1995, on the Climate Control panel, press the OFF and WARM buttons simultaneously.

On the 96/97, push the OFF button and the top (warmer) end of the PASS rocker switch.

Write down any codes that come up. You'll notice that some may be Current while others are History. Record that as well.

When the codes come to an end you'll see "PCM?"

At this point you can exit by pressing RESET. If you missed some codes and need to cycle through them again simply press OFF to restart the codes.

Someone correct me if I have the procedure wrong for the 97.

Come back and post the codes here and we'll tell you what they mean.

"Burns" rubber

" I've never considered myself to be all that conservative, but it seems the more liberal some people get the more conservative I become. "

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You can ignore the P0404 as far as your transmission is concerned.

During a test drive, can you feel or see a slight increase in engine RPM when driving at more than 45 MPH and lightly touching the brake pedal?

One of the inputs the PCM uses to "lock" the torque converter is from a brake pedal switch. I would make 100% sure that switch (there might be two) is adjusted properly and is in fact working as intended.

Not many people here would recommend a transmission flush. Drain and refill is the safe way to go and it certainly will do no harm to your transmission. Your transmission fluid is specified as Dexron III; if you can find Dexron VI, I would use that.

The P0404 could be as simple as a dirty EGR valve that can easily be removed, cleaned, and installed.


Drive your car.

Use your cell phone.


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Something doesn't sound right. How can the TCC be stuck on AND off. If it is stuck off, you can live with it. You'll probably loose about 1 MPG. If it is stuck on, you can't. The car will die everytime you stop. Like stopping a standard transmission without stepping on the clutch.

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Thanks everyone for the advice. I will double check the codes tomorrow using the method you detailed as well as the RPM's when touching the brake pedal.

The car started right up and did not die on the drive home from the shop.

I should clarify, the garage paperwork says: "performed obd system check, code po741, po404 present. found egr valve to be stuck recommend replace also found failure code po742 internal transmission approx $3265."

As far as I can tell po741 and po742 are both the TCC, so maybe it was stuck on in the past and now it's stuck off. I need to check with the state vehicle inspection office, because the garage also refused to inspect it based on those codes... :(

Again, I appreciate the advice and will check back tomorrow.


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There are a lot of reasons that can cause a P0741 or P0742 code, and many of them can be fixed completely without replacing the transmission. First, I would check the wiring and connectors on the transmission and clear the codes and see if they return. Secondly I would look for a good transmission shop that can repair the 4T80E transmission, but is not hell-bent to find gold in them thar Cadillacs. In the meantime keep up this thread -- the people here have an amazing track record of drilling down to difficult diagnostic issues and helping people get cars fixed, partucularly with good DIY people but also with those who depend on others to fix their cars.

-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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I agree with Jim, above.... where he says "Clear the codes, and see if and when they return.."

That's step one...

If a code comes back, see what you get, and go from there....

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