I have a 998 hard fault code...

[paul44224]

It's a '94 with a 4.0, 68 k miles. Also have a 157 MAF code. Replaced the MAF with a brand new unit. Still have the 157 code. Tried clearing the codes, but they came right back. Haynes manual says I have to take it to a Ford dealer to diagnose the hard fault. Any ideas or experience wit this? Thanks !

 

[97RangerXLT]

I don't have any suggestions on the 998, but likely the MAF has a bad plug or wire to it... or you may have got lucky and got a bad MAF out of the box. I would go to the junkyard and grab 3 of them and try each one.

AJ

 

[RonD]

Welcome to TRS

Ignore the 998 for now

Here is a full list of 3 digit Ford codes: https://www.therangerstation.com/tech_library/3digitcodes.shtml

You need to look up any codes, 2, 3, or 4 digit on a FULL list, so you can see the codes the computer did NOT chose, all sensors have more than 1 code

MAF has these 5
157 Mass Air Flow signal is/was low or grounded - MAF
158 MAF sensor is/was high or short to power - MAF
159 MAF sensor is/was out of range - MAF

184 Mass Air (MAF) output higher than expected - Fuel control
185 Mass Air (MAF) output lower than expected - Fuel control

So 157 would more likely be a wiring issue, 159, 184 and 185 would more likely be sensor issue, but short to power or ground can also be a bad sensor, shorted inside

The computer can't tell you whats wrong, ever, it can just tell you what it "sees" or "saw", there is no "this sensor is bad" code on any year

You can use a volt/ohm meter to test wire on any sensor or control

Unplug the MAF sensor
Clear the code
start the engine
See if code comes back, if so then its for sure wiring issue

 

[paul44224]

Thanks for the quick answers ! When I got a new MAF, I got the same 157, so I sent it back to Rock Auto, and got another one. Same reading. So, might just be the wiring. Do I check it from from the plug to where it plugs into the computer with a continuity meter? Second question would be: where is the computer? Sorry to be a pain! LOL! Haynes manual says it is on the firewall. But I can't find it. Has a bit of a rough idle, and bogs a bit when on the gas.
Paul

 

[RonD]

Its on the drivers side of engine bay down under power brake booster, between inner fender and firewall

Look at the large wiring harness between fuse box and firewall, it splits and one group goes down to computer

The 2 outside wires on MAF connector are for the heater, a 12v and a ground wire, should be full time ground and then Key on 12volts, but probably not your problem

The inner 2 wires are for the sensor

Diagrams here

 

[paul44224]

Thanks, RonD !!! I'll check it out tomorrow !