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Codes P0171 & P0174

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2004 Deville 74,000 miles

I'm getting P0171 (Fuel Trim System Lean bank 1) and P0174 (Fuel Trim System Lean bank 2) codes. I can feel the car "sputtering" and I assume it's about these codes.

My question: What is involved in having this repaired, mainly in terms of cost? Is this something I should take only to a Cadillac service center, or can another mechanic fix this for less money?

Code B0429 (Temp Control #3 Rear Circuit Range/Performance) is also recurring. I read (here, I think) that it's possibly about a crimped hose. I recently had the battery changed, which involved removing the back seat. Is this cable/hose something that I'd be able to easily see if I removed the back seat? If so, then I'm guessing I could "uncrimp" it myself. Yes?

Thanks for reading and for your expert responses!


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There all going to do it sooner or latter.

There is a rubber intake plenum between the water crossover and the intake manifold. These develop cracks in the rubber folds, typically on the bottom where engine deposits can collect.

About a $20 part. But the intake has to come off to replace.

Spray some carb/brake cleaner around this boot. Bet you find a leak..


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B0429 is for the rear temperature control actuator. It is on or near the blower motor and is a pretty common DTC. It just means that the air mix door is not exactly in the commanded position.It may not even be enough to notice.

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