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P0401, P0174, P0171 CEL Problem Solved

BigAG

New Member
Joined
November 23, 2010
Messages
4
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2
City, State
Tampa, FL
Year, Model & Trim Level
2001 Explorer Sport
Because I've gained a lot of valuable knowledge on this forum, particularly with this recent issue, I thought I would complete my due diligence by posting this thread. Now, I'm in no way, shape or form a mechanic or even mechanically inclined. However, the parts I talk about below are pretty easy to access. I had a buddy who is much more handy help me out with this process.

My check engine light came on recently and returned codes P0401, P0174 and P0171. I don't recall the exact descriptions off top but a quick search will return those. Basically P0401 is an EGR-related issue and the other two are lean codes for both banks.

To make a long story short, I found a lot of information which lead me to the following course of action. For P0401, remove and clean the EGR valve. For P0171 and P0174, everything pointed to a faulty mass air flow sensor. It was about 50/50 on whether to clean or replace the sensor. I read a lot about cleaning the throttle body in this process to removed the caked up deposits on the backside of the butterfly valve.

I decided to do the following:
1) clean the EGR valve with basic carb/choke cleaner; removing EGR valve requires replacement of the gasket; There is a metal tube that feeds into the air intake from the EGR valve. The tip of this tube had a lot of black, crusty carbon deposits. This must be removed. The tip of this tube can be found on the inside of the air intake behind the throttle body. I just reached in with a finger and Q-tip and was able to remove it all.
2) clean the mass air flow sensor (requires cleaner specific to this part)
3) clean the throttle body (also used cleaner specific to the part)

I disconnected the negative battery terminal for a half hour or so to reset the computer. Once all the cleaning was finished, I cranked the truck up, no CEL. Looks like this simple cleaning was all that was needed. Additionally, I'm hoping this improves the fuel economy. I have also noticed a little quicker acceleration.

I think I about covered it all but feel free to ask any questions. Hope this helps.
 






Because I've gained a lot of valuable knowledge on this forum, particularly with this recent issue, I thought I would complete my due diligence by posting this thread. Now, I'm in no way, shape or form a mechanic or even mechanically inclined. However, the parts I talk about below are pretty easy to access. I had a buddy who is much more handy help me out with this process.

My check engine light came on recently and returned codes P0401, P0174 and P0171. I don't recall the exact descriptions off top but a quick search will return those. Basically P0401 is an EGR-related issue and the other two are lean codes for both banks.

To make a long story short, I found a lot of information which lead me to the following course of action. For P0401, remove and clean the EGR valve. For P0171 and P0174, everything pointed to a faulty mass air flow sensor. It was about 50/50 on whether to clean or replace the sensor. I read a lot about cleaning the throttle body in this process to removed the caked up deposits on the backside of the butterfly valve.

I decided to do the following:
1) clean the EGR valve with basic carb/choke cleaner; removing EGR valve requires replacement of the gasket; There is a metal tube that feeds into the air intake from the EGR valve. The tip of this tube had a lot of black, crusty carbon deposits. This must be removed. The tip of this tube can be found on the inside of the air intake behind the throttle body. I just reached in with a finger and Q-tip and was able to remove it all.
2) clean the mass air flow sensor (requires cleaner specific to this part)
3) clean the throttle body (also used cleaner specific to the part)

I disconnected the negative battery terminal for a half hour or so to reset the computer. Once all the cleaning was finished, I cranked the truck up, no CEL. Looks like this simple cleaning was all that was needed. Additionally, I'm hoping this improves the fuel economy. I have also noticed a little quicker acceleration.

I think I about covered it all but feel free to ask any questions. Hope this helps.


Thanks for this sir, I have a P1309, P0174 and P0171, which first means I have a misfire,,,, the plugs were 125K on them so that's the thing I changed as matter of fact,,,,,,,

I used the TOAD PC Software on my OBD and put up the live graph for short term fuel trim bank 1 and short term fuel trim bank 2 and long term trim for both banks as well.....

this is cool

I saw that the fuel trim for both banks was up and down near 20% to 40% this is the attempt to regulate/correct the fuel air ratio based on engine parameters. also means its not specific to one bank or one O2 sensor,,,,,,,,

So AH HA moment high fuel trim means lean (P0171 and P0174),,,, the P1309 misfire is setting because the trim is all over the place to correct the lean condition and cannot be more specific to why.......

what overall issue can effect all cylinders? MAF, IAC, ...... easier yet "Vacuum Leak" started spraying starter fluid at idle in the usual suspect rubber hoses,,,,, came around to drivers side and it started to behave badly..... bingo hit under the EGR Valve and the Live fuel trim graphs start heading toward zero.... got it under the EGR valve near the diaphragm holes and it stalls....... start it back up and reduced the amount of spray and I can hold the graph near zero and make it stall at any time by full blast spray....

I am heading to the parts store or rockauto to get a new egr and looking forward to having a beautifully running drivetrain,,,,,

lower ball joints and its finished for another 50k....
LOL

RN
 












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