2008 Toyota Tundra 5.7 with 47K codes P171p upon warm-up and then p171 & 174p next warm-up
5.7 with 47K codes P171p upon warm-up and then p171 & 174p next warm-up
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The Toyota local dealer (44663) has no clue what is wrong. They replaced the air pump and it still codes a 171p on the first warm-up (5 miles) and p171 and 174p the next warm-up cycle (from cold). It has gone from 16mpg to 11, but reads lean both banks. I replaced the MAF sensor and 1A Auto even sent me the 2nd one free, then refunded my money. Same problem. I am now waiting for a new PCV valve as it barely closes. It sounds a bit better after cleaning the PCV and appears to have picked up a mpg or 2. I was a line mechanic a long time ago and only have a hand-held OBD tool and my wits to figure this out. I am now finding the term "service tech" troubling as the dealer's main Toyota guy told me he couldn't do anything until it throws a different code. Any help is greatly appreciated.
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P0171 lean bank #1, and P0174 bank #2 indicates a problem that is affecting both left and right banks run too lean as you noted. You should look for things that would impact both banks equally such as dirty air filter, MAF sensor, a loose or cracked air tube from air cleaner to throttle body, IAC valve clogged, throttle body or intake manifold dirty, vacuum leak, plugged exhaust, ,clogged fuel filter, clogged injectors, Low voltage or bad ground to ECM, etc. Start with the simple things such as checking air tube and cleaning the IAC valve and throttle body. Then look at live data with your scanner while an assistant drives to get more clues.
Thanks. I have done all the simple things. So did the dealer. I used propane to check for leaks and they did it with a vacuum gauge. The IAC valve seems to be an interesting thought. I am still waiting for a PCV valve from NAPA, but I think it is not the problem since everyone has to order it. This is a garaged truck that is only driven once a week or so, so I also bought some good injector cleaner thinking that may be an issue.
It is definitely not anything as simple as an air leak or dirty filter. I will pull the IAC valve off and clean it and then if that does not help it looks like I will hang another MAF sensor on it. It has to be something that is sending a lean signal to the control module. hmmm
fuel pressure test?if starving for fuel sometimes,PO171-PO174 will set.i think on your truck everything is in the tank
pump,strainer,filter,reservoir,sender,and regulator
filter/strainer could be clogged and pump still trying to work?
Thanks. I have done all the simple things. So did the dealer. I used propane to check for leaks and they did it with a vacuum gauge. The IAC valve seems to be an interesting thought. I am still waiting for a PCV valve from NAPA, but I think it is not the problem since everyone has to order it. This is a garaged truck that is only driven once a week or so, so I also bought some good injector cleaner thinking that may be an issue. It is definitely not anything as simple as an air leak or dirty filter. I will pull the IAC valve off and clean it and then if that does not help it looks like I will hang another MAF sensor on it. It has to be something that is sending a lean signal to the control module. hmmm
fuel pressure test?if starving for fuel sometimes,PO171-PO174 will set.i think on your truck everything is in the tank pump,strainer,filter,reservoir,sender,and regulator filter/strainer could be clogged and pump still trying to work?