Code 157 & MAF | Ford Explorer - Ford Ranger Forums - Serious Explorations
  • Register Today It's free!

Code 157 & MAF


February 8, 1999
Reaction score
On my 94 exp with 4.0L engine, the check engine light came on, & I have the code 157, MAF voltage low. Having access to a breakout box, I directly measured the voltage from the MAF sensor & it was below spec. Do you think cleaning the sensor filaments will get the voltage signal back to specs. If I have to replace the sensor, how does Ford sell them? The sensor itself or the entire air horn assy. What is the typical Ford price for a MAF sensor? Finally, I'm also occasionally getting a code 998 which means hard fault. What is a hard fault? I know this is pretty technical, maybe a Ford tech cruises this site.
Thanks, FJK

Join the Elite Explorers for $20 each year.
Elite Explorer members see no advertisements, no banner ads, no double underlined links,.
Add an avatar, upload photo attachments, and more!

The code 157 is very common.. normally cleaning the MAS will fix it..

You normally need a security torx bit set.. just remove the electrical connector.. then remove the security torx bits.. and pull out the sensor (it is between the air tube and the air box)..

How to clean it is slightly debated (I think there even a sticky thread on there about cleaning it)..

Just use o2 sensor safe cleaner.. Some spray right on it.. others use a q-tip (worried about breaking the sensor wire with the spray)..

This is what I found about hard faults..
Hard faults are problems that the computer has located RIGHT NOW. Examples are a sensor out of range or a broken wire (open circuit).

Hard faults are the FIRST set of slow codes output in a Key On Engine Off test. BEFORE the SEPARATOR pulse.

In a Key On Engine Running test, there are ONLY HARD FAULT codes. These are output right after the fast codes.

According to my book code 998 is "Did not pass Key On Engine Off test yet"


Mark: Thanks for the reply. I tried cleaning the MAF & it was still throwing 157. In fact, I couldn't clear it because it was an on-going hard fault. Also, you can not run a proper KOER test unless the hard fault is repaired. Today, I got a new (remaned) Ford MAF. Disconnected the battery after installation. Restarted engine, check engine light gone, no more 157 code, & the engine runs great. Engine idle was little shakey (hunting) for the first 10 minutes while the EEC was relearning. BTW, I installed a breakout box & measured MAF voltage. Obviously out of spec with old sensor and in spec with the new sensor. Now if I could only get rid of that 335,336 DPFE code. Any thoughts on that one?
Regards, FJK


I had the MAF assembley (sensor and horn) replaced by a Ford dealer last week in Kentucky. It was $151.00 for the part and $114.00 for labor.

Thanks. Yeah $151 is dealer list for the MAF. If you buy it as a service part to install yourself, they also hit you up for a $75 core charge until you bring back your old one. BTW, what where your symtoms before you got yours replaced & how does it drive now with the new one? Mine runs better then ever. Good throttle response & hopefully better MPG. We'll see.
Regards, FJK

RussellK, you got ripped off with that 114 dollar labor charge. thats a 30 minute job tops.