‘94 VAF - Replace THA pin or repair IAT circuit? (1 Viewer)

[JunkCrzr89]

My ‘94 FZJ80 is throwing code 24 - intake air temp sensor malfunction. I went through the FSM diagnostic procedures for testing resistance and it looks like the THA pin is dead. Resistance between E2 and VS is within spec, but between E2 and THA (the IAT circuit) and between VS and THA I get nothing.

As you guys know, a new VAF is NLA from Toyota. The only potentially decent replacement option I’ve found is $350 for a “rebuilt” unit from a seller on eBay (possibly junk, I know). However, if these units can be rebuilt, then I would think the dead THA pin in mine could be replaced and/or the connecting circuit repaired. But I also know that removing the two screws to pull the connector off the unit is a can of worms that may lead to a completely dead VAF. So does anyone know if this circuit can be repaired or the THA pin replaced, or should I just go ahead and get the “rebuilt” unit?

Btw - I did search and found a couple of threads but no definitive answer about this (e.g., 93-94 VAF rebuild serivces ? - https://forum.ih8mud.com/threads/93-94-vaf-rebuild-serivces.972184/#post-10808988)

 

[Irish Reiver]

I'm pretty sure if you flip the VAF over you can remove the base plate and get access to all the components inside without any of the damage that can done by removing the connector screws. You may find that the THA connector has been broken and is an easy fix...YMMV

 

[JunkCrzr89]

I'm pretty sure if you flip the VAF over you can remove the base plate and get access to all the components inside without any of the damage that can done by removing the connector screws. You may find that the THA connector has been broken and is an easy fix...YMMV

Thanks for the suggestion. I’ll check it out.

 

[Kkxrw]

what did you end up doing to fix it? thanks

 

[JunkCrzr89]

what did you end up doing to fix it? thanks

I sent it off for $100 rebuild at: Repair Service 93-94 Toyota Land Cruiser Maf Mass Air Flow Sensor Repair Service - https://massflowsensor.com/repair_service_93_94_toyota_land_cruiser_maf_mass_air_flow_sensor_repair_service.php

Works great now.

 

[arcteryx]

RE: the ebay ones. I looked at picking up some reman'd ones that you see on ebay. TLDR> They are awful, don't bother.

It bench tested ok, but when I installed it in my 94, it could hardly make it up a small hill. It had no power until 3K RPMS and I could hardly get over 55. Needless to say, I declined to carry them.

I have not used the repair service mentioned above, but that may be a good option if it checks out

 

[Kkxrw]

Thanks

 

[Inukshuk]

I'm pretty sure if you flip the VAF over you can remove the base plate and get access to all the components inside without any of the damage that can done by removing the connector screws. You may find that the THA connector has been broken and is an easy fix...YMMV

All the components you need to access are under the black plastic top cover. Use a utility knife to remove the silicone and the cover pops out. I just did it. Mine is sitting open right in front of me as I type. The top section with all the components you need to access are separated from the lower half by metal integral to the casting. No access to the top components is possible from removing the base plate.

As noted everywhere - do not remove the screws for the connector.

 

[Irish Reiver]

All the components you need to access are under the black plastic top cover. Use a utility knife to remove the silicone and the cover pops out. I just did it. Mine is sitting open right in front of me as I type. The top section with all the components you need to access are separated from the lower half by metal integral to the casting. No access to the top components is possible from removing the base plate.

As noted everywhere - do not remove the screws for the connector.

If you still have yours open it would be nice to post some photos so others can relate to what is mentioned in the thread.

 

[sogafarm]

If you still have yours open it would be nice to post some photos so others can relate to what is mentioned in the thread.

Here you go.

Pulled the cover off the maf sensor so far. I adjusted the little tabs resting inbetween the three horizontal prongs(plugs #3,4,5) and the circuit board coming from the plug end. Looks like I had pulled the factory solder away from the circuit board when I originally pulled the plug out by mistake.
Next will attempt to solder the tabs to the circuit board.

Question....Do I solder just the tabs to the board and the prongs float on top or do I solder the prongs through the tabs to the board? In other words should the prongs coming from the plug just sit on top of the soldered tabs or should they be permanently soldered all together and to the board? I'm not sure what these three prongs are designed to do, but I do know they must be crucial to the fuel injection system somehow.

Also, do I need to reset the ECU by unplugging the battery or another method?

View attachment 2136412

View attachment 2136413

 

[Inukshuk]

If you still have yours open it would be nice to post some photos so others can relate to what is mentioned in the thread.

You bet. I will once I figure out what it should look like because mine has an issue. Hopefully soon I will open a known good one I have.

 

[Timpanogos Slim]

You bet. I will once I figure out what it should look like because mine has an issue. Hopefully soon I will open a known good one I have.

It looks like just a specialized potentiometer.
You need to be gentle with the carbon track. You could slide a thin piece of plastic under the metal wiper and then wet a piece of paper with contact cleaner and slide it between the wiper and plastic several times.