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96 CE giving codes p0171 - p0174 Bank 1 and 2 lean

gmhowe

Well-known member
Joined
Nov 14, 2002
Messages
437
Location
glendale, az
Corvette
1985 4+3 black cpe & 96 LT1 CE
I looked up past threads on these and seems only 2 options - Through in a bottle of Techron and replace the fuel pump. Engine light doesn't stay on all the time. Any other options or just replace the pump and see what happens.
Gordon
 
What steps have u taken so far? The coupled codes indicate a possible intake leak, front O2's, air filter etc.
 
Put a pressure gauge on it and check the fuel pressure before you buy a new pump.
 
Actually haven't had time to do anything, want to check the vacuum before doing anything else. Still replacing the headlight motor on my 85 vette along with fixing the inside door handle, so many things to work on.
 
But if there were issues with the O2 sensor wouldn't kick out their own codes for them ?
 
But if there were issues with the O2 sensor wouldn't kick out their own codes for them ?

I would think a lean condition could be caused by an 02 sensor. Not necessarily that the 02 isn't working but it may be lazy. Definitely check for vacuum leaks and anywhere air might be getting in as a first step. Seems odd both banks are lean at the same time. Did you have the codes when u got the car? Also look at the mileage on the O2's. Mine had to be changed out at 80K.
 
Yep I thought it was strange that both happened at the same time, so how do you determine which one it is ( sensor that is ) since there are 2 before the cat. converter and 2 after it ? they run about $45 a piece.
 
Yep I thought it was strange that both happened at the same time, so how do you determine which one it is ( sensor that is ) since there are 2 before the cat. converter and 2 after it ? they run about $45 a piece.

The two upstream actually do the adjusting, the downstream (rear) check that the cats are working. Again mileage on the car determines if you should replace all four. But I myself worry a lot less on the back ones. Good idea to replace the front two. My opinion anyway.
 
ended up being a crack in the Brake booster and both knock sensors
 
ended up being a crack in the Brake booster and both knock sensors


You said you were going to get around checking for vacuum leaks first. Seems like this is an issue 90% of the time with all vehicles when you get mixed codes. Glad you found the source of your problem. It's always good to kick ideas around in your head before you do anything.
 
It's important to note that the existence of both these DTCs indicates a problem affecting both banks.

First to look for are any leak were intake air can get into the engine without going through the MAF. Obviously, this can be vacuum leaks, but it also could be a leak between the TB and the MAF.

Unlikely this is lazy O2Ses as 1) it would be highly unusual for both sensors to fail the same way and 2) if there was a lazy sensor, it would set DTC P0154 or P0160 which are the two codes for insufficient activity codes from Bank 1 or Bank 2.

Again, check for vacuum or air leaks anywhere behind the MAF. Check for any exhaust leaks near the O2Ses.

Once you check for leaks and don't find any, you need to do all the steps in the "Fuel System Diagnosis" in Book 1, page 6-313 of the FSM.

One solution to these codes is a faulty fuel pump. A more likely solution is a new fuel filter. There are numerous other solutions, too, such as faulty injectors, restricted fuel pipes, faulty fuel tank pickup, bad FPR or fuel pulse damper.

Unfortunately, the 1996 FSM is out of print. You'll have to look on eBay or a place like Faxon Automotive Literature which has used '96 FSMs for 130-140 bucks.
 
I actually have the FSM for both my vettes 85 and 96. The shop showed me the crack in the booster and the codes haven't come back on. The shop I use was voted by VETTE Magazine one of 2 best shops here in the Phoenix area for working on vettes. Funny the car would still run like a bat outta hell when the codes were showing, so I wonder if there was a fuel problem. I checked for leaks around the MAF found nuthin and none around the TB. My 96 has 126k miles and my 85 just passed 86k. Just wish the 96 was a little higher on the front end since I quit buying the spoiler after spending money on 3 of them.
Thanx guys as usual for all your help and ideas
Gordon
 

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