Longtime lurker, first time member. Sorry for this novel, skip down for my current problem - I feel the troubleshooting steps I've taken up until now are important to know, though.

I bought a 94 in Feb, 4.0L Automatic. I've been throwing parts at it (I know, I know)... BUT the EEC-IV never would communicate with scanners, so I relied on the jump-wire method to get my codes. I've knocked out several codes, and I finally got down to 1 last code (136 LEAN / HO2S not switching -- yes both O2 sensors and all suspects replaced already, and checked for vac leaks). THEN I discovered it's the 4L, not the 3L as the seller had stated (I know, I know... i should've checked the VIN earlier).

Anyway, I began racking my brain on which parts I've thrown at it that may have been incorrect for the 4L. Spark plugs had a different heat rating. So I replaced those, and here's where my major problems happened. On first startup, everything went haywire, engine sputtering, barely staying on, dying eventually. Yes I've checked that I didn't mess up wiring order, and only had 1 plug off at a time anyway, to prevent that. Checked codes again. Now i get 998 Hard Fault/"limp mode", and 157 "MAF circuit voltage below minimum". (No longer had code 136). Not sure if pertinent here, but the 2 new codes flash the light BEFORE the engine indicator flash.

As a troubleshooting step, I also switched back to the 3.0L Plugs... since the truck at least was drivable with those... however the same codes and problem are STILL there with the old plugs, so i know the new ones weren't the culprit. Checked for hoses I may have bumped loose, all looks good. MAF was new, but cheap from amazon. RE-replaced it with a more name-brand one. Same problem. Installed new wires (2 of the old ones were bad, 1 showing ZERO ohms). the problem remained. Next I pierce-probed the MAF's 4 wires - voltage is good, but I don't have an RPM gauge to measure voltage per RPM level. I'm down to my last straw, and on a whim I suspect that because the EEC-IV never would communicate, maybe the ECM computer was going out and got worse?? I know bad ECM's are rare though.

Sorry for the novel, here's my current situation: I now have the ECM out, and can only seem to find my exact OE number on RockAuto, but even there they have a discrepancy. Parts stores near me do not have the xxxx-xxxxxx-ANB version at all. RockAuto DOES, but the 4th digit is not an F, it's a Z. I've read RonD's explanations of the OE #s on ECM'S, which helps but also adds to my confusion:

Current ECM #: F47F-12A650-ANB
ECM on RockAuto: https://www.rockauto.com/en/moreinfo...=2896&jsn=1378

• Listing states: OEM / Interchange Numbers: F47FANA, F47Z12A650ANA, F47Z12A650ANB
  Why the Z?? RonD I hope you see this, I've learned from you that "F = General Parts/Electrical and Electronics Division".... so what Does Z mean??
  • Will this still work for me?
  • Is there a parts store I can get the right part at after all, since I haven't had good experiences with RockAuto??
  
  Thank you for any and all help! I am desperate to get this baby running and tired of throwing parts.

 

wow! good luck! I have nothing to add at this time.

 

Wow thanks.

For those seeking help on the same issue, yes the ecm fixed my problems.

 

Welcome to the forum

Well 1st post on the forum

OPEN the computer up and check its 3 capacitors, blue ones as seen here: Ford EEC-IV

Simple fix if any are bad, under $5, replace ALL 3 with black ones

F47F-12A650-ANB

F4 = 1994
7= Ranger or Mazda B-series
F = department at Ford responsible for the part, electronics depart.

12A650 = actual part number for ANY engine computer in any year and in any model of Ford, still used in 2023

ANB = revision and software, important since it also denotes engine size, manual or automatic, EGR or no EGR, Cam sensor or no cam sensor
Ford NEVER released a cross reference for this suffix ID

Best place I found to see "what works in what" is: https://www.car-part.com/

1994
Ford Ranger
Computer Box Engine
USA
skip area
YOUR Zipcode
SEARCH

New window opens, this is where you match YOUR Ranger and its current computer
They call these electronic control modules and I see
"Electronic Control Module, 6-245 (4.0L), 4x2, AT, ID F47F-ANB" <<< your number
The 12A650 is never included since its the same on ALL Fords, lol

So according to your number you have a 4.0l engine, 2WD(this doesn't really matter) and an automatic transmission(AT)

So any of these would also work
Electronic Control Module, 6-245 (4.0L), 4x2, AT, ID F47F-CKA
Electronic Control Module, 6-245 (4.0L), 4x2, AT, ID F47F-CPA
Electronic Control Module, 6-245 (4.0L), 4x2, AT, ID F47F-CPAMR
Electronic Control Module, 6-245 (4.0L), 4x2, AT, ID F47F-DDA
Electronic Control Module, 6-245 (4.0L), 4x2, AT, ID F47F-DDAMR

I don't see an ANA but it might work, the lists at car-part.com are from wrecking yard records, "what came from what" over the years, so won't have every computer number Ford ever made

You can select one of the above and SEARCH but these will be almost 30 years old as is
The refurbished one will also be almost 30 years old but will have been cleaned with new capacitors installed
1994 was the last year for this type of computer so ALL will be at least 29 years old