Question about 1999 Ford Explorer

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Code #P0171 & code #P0174

1999 ford Explorer XLS with original 65,000 miles
4.0 SOHC 4wd

The codes in the subject line stipulate that bank 1 & 2 are too lean. Replacing the following parts did not fix the problem.

Replaced MAf sensor & check engine light came back on
Replaced right bank & left back 02 sensors & check engine light came back on. The

Please help if you can.......James

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  • dnyswonger Jun 22, 2008

    We are just getting P0171, we have cleaned the maf and reset the code I will come back in a few days Not right away. I have a innova scaner. we did a live data link and took it for a test after we cleaned the maf and reset The only thing that was out of line was the o2s b1 s2 was only going from 0.06 to 0.100 all the other o2 sensors were going from 0.300 to 0.750

  • Anonymous Mar 14, 2014

    A month ago CEL came on for p0171 system too lean bank one CEL turned off by itself next day. Two weeks ago car wouldn't start replaced PEM fixed it! Next day CEL comes on for p0191 fuel rail pressure sensor, so I replace the FRPS. CEL doesn't come back till 10 miles after driving?

  • Anonymous Mar 17, 2014

    I have a 1999 ford f-150 with a P1309 code I'm trying to get inspected. Last year the dealer replaced the cam sensor and synchronized. Said problem was fixed. One day later light came back on and now this year it's the P1309 code. Every year light is on and i am charged large amounts of money only to have light come back on within a day. help

  • Anonymous Mar 19, 2014

    replaced o2 sensors codes and check engine light came back

  • Anonymous Mar 19, 2014

    Codes appear o2 sensor change still check engine light.


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The most common problem on a Ford with these codes is deteriorated PCV hoses. Check the hoses from the PCV valve to the intake manifold. Pay special attention to the rubber elbows. They often crack on the inside curve and the crack is hard to see.

Posted on May 22, 2008

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1998 ford explorer with a rich/lean code

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Look, man here is the deal:
code p0174 - refer to the front cylinder bank
code p0171 - refer to the rear cylinder bank

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