4.0 SOHC WITH 174 B2 AND 171 B1 CODES

2000 Ford Explorer

2000 Ford Explorer XLT 4wd 4.0 SOHC -
Codes are 174 B2 and 171 B1 -
check engine light is on and Idle is low / erratic
No other symptoms. How do I fix and does this truck have MAS or MAP
December 20, 2006.

Hey Ford,
The most common issues for those 2 codes at the same time are: 1. Bad intake seals (upper and lower) A quick test is to carefully spray carb cleaner at the mating surfaces with the engine running, if the idle smooths out then you've got the issue nailed!

2. Faulty Mass Air Flow Sensor and there is no quick and easy test for this. It may also be just a dirty MAF, try some electrical cleaner and Q-tips, carefully clean the tiny " coils" that you see (with the maf removed from the air box) Let us know!


Dec 21, 2006.

Thank you for your advice it is great advice.

I sprayed air intake cleaner before and after MAF and didn't notice a difference in the idle. I checked the voltage supplied to the MAF wire harness and its OK. I pulled the section and checked the resistance between the second and third and fourth and fifth pin on the MAF will little resistance 3 ohms or so. I also tried to spray clean the element in the MAF. I chaged the air filter while I was there and cleared the codes by pulling off the positive battery cable for a minute. Idle is 500 to 700 or so.

I'll let you know what happens.

Dec 21, 2006.

I was wondering what you found out and what is or was the fix to this problem.

Thanks for your advice.

Dec 31, 2008.