**SOLVED** Codes 24 & 31 on 1994 FZJ (1 Viewer)

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Update: Replaced the VC and the oil loss is resolved. After a shakedown run of about 50 miles, my intake tube and throttle body are absent of oil. Hooray for that but the intermittent code 31 and 24 still persists. I'm now on the hunt for a VAF and/or ECU...Wish me luck!
 
Update: Today I got @shocktower VAF he sold to me. He's a great dude and I'm thankful.
Here are some pics. Let’s see if you can spot a difference. The one off my cruiser is on the right.
467B4AED-18BF-45F1-9E4D-F1FB5F94702F.jpeg
The one off my cruiser is cleaner and looks to have been painted. Which got me thinking. Here is the bottom of mine. You can zoom in and see where it has been painted if it isn’t obvious already. I suspect this VAF has been opened and tampered with by an eBay dude who sells refurbished VAFs. I also bought and returned a VAF he sold me. I don’t want to say anything publicly so if you want my experience, PM me and I’ll share
Thanks again to @shocktower for helping me out.
751253FA-B5D0-4C56-B630-09E8FC2F7924.jpeg

Here is the one shocktower sent me:
5F2FD252-1832-4F16-A23B-10DFAF156C3A.jpeg

Now that I have both VAFs side by side, I began comparing values. When shooting for continuity on pins E2 and VS, both VAFs got similar values with the door closed and full open.
Then I compared pin THA on both VAFs and looks as though my THA pin off the cruiser is dead. I shot this the last time and it was functional but it has since failed as I’m shooting open every time.
It never occurred to me that my VAF looked a little too good. I have never seen another VAF so that’s my alibis.
Bottom line, I think this is the culprit but time will tell.
 
I’m updating this troubleshooting thread. After 300+ miles in various terrain, speeds, temps, I haven’t popped any codes.

The solution was in fact a new-used VAF. The problem initially was difficult to isolate due to the intermittent faults and lack of consistent failures when driving. The problem would present itself differently too, in fact sometimes my idle would stutter, sometimes the engine would die when driving, other times the problem happen at highway speeds.

The issue was further exacerbated because when performing the installed and uninstalled functional checkout per FSM, the VAF consistently shot good.

Well as I indicated in the previous post, the THA pin was finally dead and replacing the VAF was the solution.

Thanks to @sogafarm @Irish Reiver and @Landseer for help throughout this process and also to @shocktower for selling me the VAF.

I’ll update if anything happens but I doubt it will.
 
Glad that it was any easy fix. I'm curious as to what the inside of the original VAFM looks like. Since it has been opened before, could you pull the black plastic cover off and take a pic of what the internals look like. I'm thinking that the little flat metal arm that makes contact with the clock spring at close was bent or not making good contact and that was why it was intermittantly cutting off.
 
sogafarm said:
Glad that it was any easy fix. I'm curious as to what the inside of the original VAFM looks like. Since it has been opened before, could you pull the black plastic cover off and take a pic of what the internals look like. I'm thinking that the little flat metal arm that makes contact with the clock spring at close was bent or not making good contact and that was why it was intermittantly cutting off.
Click to expand...
I’m curious too, I’ll look up how to do it and see if I can provide the mudship a worthy contribution. Expect to see something soon, maybe today but no promises.
 
The little black cover will pry off once the sealant is cut away. Just take a pick or similar to pry up the cover. Here was what mine looked like after my attempt at resoldering the tabs. Yours may be worth saving for a spare. My bad one still works but it shows code 24. I replaced with a good used and now have the original as a spare. These VAFM's seem to be the biggest weak link in the older obd1 cruisers and it would be good to have a working fix for people in the same situation.
IMG_1370.JPG
 
sogafarm said:
The little black cover will pry off once the sealant is cut away. Just take a pick or similar to pry up the cover. Here was what mine looked like after my attempt at resoldering the tabs. Yours may be worth saving for a spare. My bad one still works but it shows code 24. I replaced with a good used and now have the original as a spare. These VAFM's seem to be the biggest weak link in the older obd1 cruisers and it would be good to have a working fix for people in the same situation.
View attachment 2789528
Click to expand...
Did you repair it yourself and did it Ops check good?
 
FMC80 said:
Did you repair it yourself and did it Ops check good?
Click to expand...
I boogered that one up all by myself. Yours looks like it was booger soldered as well. I didn't do any meter testing. I did the trial and error method. I got very good at taking it out and putting it back in to test the fix. Overall, my old half-ass repaired one does work fine, just has the 24 code, no other problems. I need to upgrade my soldering iron though. You can read about my VAFM journey here: My first 80 - https://forum.ih8mud.com/threads/my-first-80.1170546/ @slow95z and @ppc were big help. In hindsight I should have jumped on the used one that slow95z offered, but in the spirit of rebuilding not replacing I gave it a shot. I later found another used one for sale and just replaced the original.
 
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sogafarm said:
I boogered that one up all by myself. Yours looks like it was booger soldered as well. I didn't do any meter testing. I did the trial and error method. I got very good at taking it out and putting it back in to test the fix. Overall, my old half-ass repaired one does work fine, just has the 24 code, no other problems. I need to upgrade my soldering iron though. You can read about my VAFM journey here: My first 80 - https://forum.ih8mud.com/threads/my-first-80.1170546/ @slow95z and @ppc were big help. In hindsight I should have jumped on the used one that slow95z offered, but in the spirit of rebuilding not replacing I gave it a shot. I later found another used one for sale and just replaced the original.
Click to expand...
Yep, I remember reading your thread. I'll keep the malfunctioning VAFM and see about sourcing another one. I really want a new one but someone swiped them all and I missed out.
 
FMC80 said:
Yep, I remember reading your thread. I'll keep the malfunctioning VAFM and see about sourcing another one. I really want a new one but someone swiped them all and I missed out.
Click to expand...
I thought onur had a new for sale.
 
There sure doesn't seem like much to it. I see a contact that I assume opens at minimum and the sliding rheostat that moves with the vane.
 
FYI and FWIW. What I learned so far and please excuse any translation gaffes between the smart person that explained it to me and the jabronie explaining it to you. Those three pads on the PCB where the pins from connector attach aren't "normal" pads, but they were manufactured with a dry film on the pad containing the traces. When you try to re-solder on those pads, you are most likely destroying the conductive dry film with the heat and making things worse. (You can see the remains of that film sticking to the connector pins on my one pic.) So the challenge now is not to try soldering the connector pins back onto those non-conductive pads, but to figure out how to solder the pins directly to the traces on the board. This is probably why above it took a few tries soldering them back on before a connection was made.
 
FMC80 said:
Dudes,

Here's the background: My truck is running pretty great. Solid idle and acceleration, no hesitation. This may or may not be related to the main issue but on very few occasions, my idle will wander and fluctuate approx 200 rpm up and down the range. A little throttle and the problem goes away.

The main issue: On three separate occasions over a 2 month period, my truck died for no discernable reason.
1st time, 2 months ago: Rolling with light throttle, approx 15 mph and I saw the CEL illuminate then the truck died. I started it immediately and it drove just fine thereafter. No CEL and no codes after jumping the diag port.

2nd and 3rd time happened consecutively today. After about a 20 minute drive, I pulled over and was idling. I saw the CEL illuminate and then the truck died. I started it back up and it died again. After looking around the engine bay pretending to know what the hell I was looking at, I started the truck and it drove fine for the rest of the entire day.

When I turn the ignition to "on" I have the CEL. I installed new fusible links about a month ago as PM.

After getting home, I jumped the diag port and got 31 "Volume Air Flow Signal". I checked the FSM and did basic ohm outs on the VAF and all checked within limits. After reinstalling the VAF harness, I checked the diag port again and this time I have a 31 and a 24 "Air intake temp sensor signal" fault.
View attachment 2731771

Now, I never messed with my VAF except to clean it and put some dielectric grease on the connection. I never messed with screws or anything of that sort.

Aside from the diag port telling me I have codes 24 and 31, my truck drives fine and the CEL is not illuminated at all.

My truck has a new fuel filter, the main engine harness was inspected and gtg, EGR is disabled, all new plugs, wires, distributor, timed to 3*.

Finally, aside from checking for continuity, and removing and reinstalling the EFI fuse, what else can I do? I've searched through the archives and maybe my google-fu sucks so I'm looking for any assistance you can provide.

Cheers,
Pell
Click to expand...

@FMC80 is there a mistake in manuals table? The two first line in the table reads the same pin different resistance???

vaf.png
 
Desert Dino said:
@FMC80 is there a mistake in manuals table? The two first line in the table reads the same pin different resistance???

View attachment 3040373
Click to expand...
I noticed that when I was troubleshooting mine as well. I am not sure why it’s like that beyond temperature values determining the differences.

I don’t have the FSM in front of me but there is another chart that has the correct troubleshooting format with proper values so I used that one instead. You should be able to cross reference the troubleshooting steps to find it.
 
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