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I can't get my check engine light to stay off, showing lean bank 1&2 code...


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markg
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May 5, 2017, 12:50 PM

Post #1 of 24 (977 views)
I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

I have a 2001 Chevy Silverado p/u 1500, 4x4, 4.3 engine with about 130,000 miles.. I had to replace the spider injection assembly, now my check engine light came on and it's showing a 171-174 code, lean bank 1 and 2. Went down the list of things that could be the problem and it still won't stay off. Fuel pressure is over 50lbs, no vacuum leaks and put on a new mass air flow sensor. I turn off the check engine light and it come back on after a mile or two down the road, I don't know what else to look for, I checked everything the scanner told me to and the engine light stills come on. Anyone have any ideas what I should check for next? Could the new spider assembly be defective?


Discretesignals
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May 5, 2017, 12:53 PM

Post #2 of 24 (974 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

Does your scanner show engine data? If it does, what are the long and short term fuel trims at idle?





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


markg
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May 5, 2017, 4:36 PM

Post #3 of 24 (951 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

I don't know what the fuel trims are at the moment, I'll see if I can get that info for you. The guy who is working on it has a auto repair business, he's been doing repair work for years but he said this problem has him baffled. He said he tried everything he knows and checked out everything the scanner said that may cause the problem and we come to a dead end. I started showing this code right after we put the spider assembly in, that's why I thought maybe it had a defect. I thought I'd try to find out online if there was something we missed checking before pulling the intake back off again. I'll see if I can get that info for you and we can start from there, thanks...


Hammer Time
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May 5, 2017, 4:54 PM

Post #4 of 24 (945 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In


Quote
He said he tried everything he knows and checked out everything the scanner said that may cause the problem and we come to a dead end



If he is relying on the scanner to tell him what the problem is, then you have the wrong mechanic.

50 PSI is actually too low on the fuel pressure. The spec is 55 to 62 and the engine is very fussy about that. Find out why it is so low.

You might even rig up a gauge and drive it that way to see if it's dropping even lower.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



(This post was edited by Hammer Time on May 5, 2017, 4:55 PM)


markg
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May 5, 2017, 5:28 PM

Post #5 of 24 (938 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

Is 55 to 62 lbs pressure at idle or driving? I'll hook up an pressure gauge and let you know what I get. I was thinking maybe the fuel pump was starting to go or a dirty fuel filter, would that cause the problem?


Hammer Time
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May 5, 2017, 5:31 PM

Post #6 of 24 (936 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

It should be within that range at all times.

A clogged fuel filter will lead to pump failure but it won't be the sole cause of low fuel pressure.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



(This post was edited by Hammer Time on May 5, 2017, 5:32 PM)


Tom Greenleaf
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May 6, 2017, 1:45 AM

Post #7 of 24 (907 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

A reason of several for low fuel pressure can be low voltage/amps delivered to fuel pump. Would be nice to watch live both voltage alone enough while cranking stays above 9V and always above ~13V at idle, driving and items turned on.
Is there something you added that draws more power than the truck's charging system can keep up with which should first give you a "battery" icon if only part time at first fuel pressure drops below spec and harms info on what to deliver when it's correct. That would cause confusion for the tech if that much shows proper when checking.


Would run lean which also mean incomplete burn if long enough set hard codes (light stays on) sensors fouled continue sending wrong info but alone not the fix the result of the low fuel pressure.


Watch fuel pressure and if any chance the voltage too, not just trucks gauge but a real reading.


FYI - motors (about any) connections on way to fuel pump can go weak if so harming those and relays involved making the problem persist.


The fix process is going to be finding a source cause then fix what that may have damaged. Proper sequence of fixes or it would all come back again wasting parts already.


Who's really working on this you or the mechanic who is lost with this? IMO this began with low fuel pressure and WHY hasn't been found,


T



markg
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May 6, 2017, 5:09 AM

Post #8 of 24 (898 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

I'm going this morning to see my mechanic and we'll pull another fuel pressure check, I'll also see if we can check the cranking and idle voltage. He did say he checked my battery and the reading did come up "Low", maybe I should put a fully charged good battery in and see if that makes a difference. The battery I have in the truck is pretty old, been in there for years, I only drive this truck in the summer and it always starts in warm weather, but I do notice in the winter I have to start it every week or the battery will go dead. My mechanic is the one who is lost finding out what's wrong, I'll print out your post and show it to him so he has a better idea of whats going on, I'll be back in touch, thanks..


Tom Greenleaf
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May 6, 2017, 5:27 AM

Post #9 of 24 (894 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

Reason I ask about "delivered" battery voltage is electric motors (fuel pump included) is expecting over 12V to prime and while cranking in two seconds will drop you can watch that and if all else is normal if that drops too low everything in the car is also getting low voltage. If it started in commonly 2 seconds then alternator put back into battery what it took to crank it then you really are running on alternator voltage.
The now possible parasitic draw (not certain yet) that it doesn't start on it's own suggests you either charge it with a charger or jump start it no longer a real great thing to do or worse if often.


Battery will flake like dandruff from this swing of being low to fully charged which makes a pile of dust unseen at the bottom. You both lose those particles and the pile builds up. When that pile of crud/dust can touch even a hair it can drain the battery by itself out of the vehicle even.
So what can happen is you overwork alternator too much also harms battery too then the result is funky behavior that escapes checking sometimes in a case like this don't trust a battery if gone low and was fairly new even - they aren't meant to tolerate that like "cell phone or device" batteries we use. They can go stone dead and come back and expect it,


T



Discretesignals
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May 6, 2017, 7:57 AM

Post #10 of 24 (884 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

Scan tool data is a very important tool when it come to diagnosing driveability issue. A good tech can interpret that information and use it for direction. Fuel trim can tell you a lot how the PCM reacts under certain circumstances. Scan tool data coupled with​ testing systems is essential, so I wouldn't go saying a mechanic that relies on scan tool information doesn't need to be working on vehicles.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


Hammer Time
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May 6, 2017, 8:03 AM

Post #11 of 24 (880 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

That's not at all what I said DS.

He stated the mechanic "did everything the scan tool told him to"

The scan tool does not tell you what to do. It merely supplies information to apply to diagnostics.

It sounds to me like he was relying on the troubleshooter totally with no input of his own or one of those "the code told me to change the ---------".



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



(This post was edited by Hammer Time on May 6, 2017, 8:05 AM)


Tom Greenleaf
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May 6, 2017, 8:20 AM

Post #12 of 24 (873 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

Back a bit. OP said up top fuel pressure was noted (by this mechanic) over 50? How much unknown. If low it will run like crap and cause the issues. My point was how it could run low and NOT be a fuel pump alone but then if low (any reason) you'll get your lean codes and crap while it still runs more will come too. Source problem first or play ping-pong tossing parts is what I'm trying to avoid or rule out a mistake,


T



markg
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May 6, 2017, 9:42 AM

Post #13 of 24 (866 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

Ok just got back from my mechanics and asked about all the questions on here. Fuel trims are all correct and in spec, did another pressure test, 65lbs before cranking motor, once started running at around 56+. When we rev up the motor it'll drop to around 52-53, truck runs great even on the road. If this helps I can tell you the fuel filter has never been changed ever since I got the truck over 10 years ago, figured I never had a problem with it running so I never changed it which I should have done. Well keep the ideas coming, we're still at a loss. He doesn't want to keep putting new parts on until we can get close to pin pointing what may be causing the codes to trip, thanks...


Hammer Time
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May 6, 2017, 9:47 AM

Post #14 of 24 (862 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In


Quote
Fuel trims are all correct and in spec,


Not even possible, assuming you didn't just clear the computer.

The actual definition of P0171 and P0174 is that the fuel trims have reached their maximum ability to adapt so you can't have the codes and perfect fuel trims.



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markg
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May 6, 2017, 11:41 AM

Post #15 of 24 (852 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

He said he cleared the code and took it for a test dive, during the drive he watched the pressure gauge and scanner and everything was in spec. Even after the light came back on he check the history and said everything stilled looked it spec but it always shows the 171 and 174 code. I'm beginning to think maybe I should take it somewhere else and have them look at it, maybe they can figure it out.


Hammer Time
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May 6, 2017, 11:57 AM

Post #16 of 24 (850 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

I think you should too. Those things totally conflict with each other. You can't set the code without the fuel trims moving.

Not much of what he is telling you is adding up. He didn't even have the fuel pressure right.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



markg
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May 6, 2017, 1:24 PM

Post #17 of 24 (841 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

Ok just for my own curiosity what would be the first thing to look for when showing a 171-174 lean bank 1&2 code?


Discretesignals
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May 6, 2017, 2:14 PM

Post #18 of 24 (837 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

First would be freeze frame data to get an idea what the engine was doing and what the conditions were when the code set. Then watch fuel trim information at various loads and engine speeds to determine which direction to go to isolate the cause.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


markg
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May 10, 2017, 3:29 PM

Post #19 of 24 (808 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

I'm going to bring it to another repair shop and have them check out everything again. They said one of the problems to look for is maybe the fuel pump is going bad. I had 65lbs with key on and 51-52 at an idle, revved the engine and it'll peek 65 lbs. It use to start right up by just turning the key, I've notice its getting harder to start, sometimes I have to try twice, maybe the fuel pump going bad?


Hammer Time
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May 10, 2017, 4:13 PM

Post #20 of 24 (806 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

Before

Quote
Fuel trims are all correct and in spec, did another pressure test, 65lbs before cranking motor, once started running at around 56+. When we rev up the motor it'll drop to around 52-53, truck runs great even on the road.


Every time you post the test results are different. Which is it?

Now

Quote
I had 65lbs with key on and 51-52 at an idle, revved the engine and it'll peek 65 lbs.




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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



markg
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May 10, 2017, 5:31 PM

Post #21 of 24 (798 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

Sorry I wrote my reply incorrectly, this problem is getting me so ticked off I can't think straight anymore, lol.. Old mechanics fuel pressure test with key on, 65lbs, engine idle 56+, rev engine 51-52. Bringing it to another shop and have another pressure test and scan done, maybe the first guys pressure gauge didn't read correctly. I'll have the new mechanic check out everything again and write it down. One thing I do know for sure is the truck is taking longer to start..


Hammer Time
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May 10, 2017, 5:33 PM

Post #22 of 24 (796 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

We're back where we started. That fuel pressure is too low.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



markg
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May 12, 2017, 4:46 PM

Post #23 of 24 (762 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

I agree, I think the fuel pressure is to low too but the mechanic keeps saying as long as it doesn't drop below 50lbs I'm ok, he said that's what the specs are. I looked myself for the fuel pressure specs online and everyone is different. Would you know where I could find the correct specs so I can show this guy, I think that spider injection needs more than 52lbs to fire correctly. One other thing I'm going to check too, I read that a sign your fuel pressure regulator could be going bad if you smell fuel in your oil. I gave it an oil change about a month ago, oil right up to the line. I just checked it and I can smell gas in my oil and now it's above the line, feels thin and also my oil pressure is getting lower. You think I should replace the fuel pressure regulator first before replacing the fuel filter and pump? I appreciate all the help, thanks...


Hammer Time
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May 12, 2017, 5:00 PM

Post #24 of 24 (755 views)
Re: I can't get my check engine light to stay off, showing lean bank 1&2 code... Sign In

First off your mechanic is an idiot. If he was for real he would have access to the same factory specs that I do. The spec is 55 to 62 as I stated before and 50 PSI is a problem.

Stop trying to make wild guesses here and find a mechanic that actually knows how to test this stuff. There are basic tests that can confirm or eliminate a regulator issue. You shouldn't have to teach your mechanic how to do his job.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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