P0401 code and the air conditioner (1 Viewer)

[peytonkristen]

I have read many of the posts and my FSM so bear with me. My 97 has occasionally thrown the P0401 code and I have cleared it. Now it seems to be throwing it on a regular basis......but only when I turn on or run my AC. So before I start going through all of the steps to possibly find the culprit I was wondering if anyone else has had the same situation. I'm hoping because it only happens with the AC that it will be narrowed down to one area.

Has anyone had this particular problem? Thanks for the help!

 

[Clemson TLC]

My EGR VSV fails when hot. No P401 in winter, only in the summer. Others owners have had the same issue. When the VSV fails open, the EGR valve does not operate (control vacuum is vented to atmosphere). The only way the AC is related is you use it in hot weather or use may cause the engine to run even hotter.

If your VSV fails when hot; taking a long trip in hot weather (gets it hot), then several short trips (start cycles when it is already hot/failed) will set the P401 code.

There is a connector in front of the throttle body that you can use to apply voltage to the VSV to determine if it fails when hot.

See vacuum and wiring schematics in FSM.

 

[peytonkristen]

My EGR VSV fails when hot. No P401 in winter, only in the summer. Others owners have had the same issue. When the VSV fails open, the EGR valve does not operate (control vacuum is vented to atmosphere). The only way the AC is related is you use it in hot weather or use may cause the engine to run even hotter.

If your VSV fails when hot; taking a long trip in hot weather (gets it hot), then several short trips (start cycles when it is already hot/failed) will set the P401 code.

There is a connector in front of the throttle body that you can use to apply voltage to the VSV to determine if it fails when hot.

See vacuum and wiring schematics in FSM.

Thanks Clemson!

I'll give that a shot in the next couple weeks.

 

[Clemson TLC]

Also see this thread:

https://forum.ih8mud.com/80-series-tech/111750-alternate-egr-tests-p0401.html

Good Luck

 

[plutonius]

I'm running into P0401 code-throwing under these same circumstances - hot days, AC on, watching the Scangauge temps climb from 176 up to 190, and bingo it throws a P0401. I put a multimeter to the VSV wiring and am getting zero resistance (see checking vsv the easy way), and as I am somewhat confident the rest of the system is in good shape, I'm putting my money on a new VSV for EGR.

That said, my Toyota OEM parts guy gave me two numbers, for two VSV's. I see 'em both on Amazon but I'm fine rolling down to Toyota or ordering from a mud vendor. Anyone who knows which is which, please chime in.

90910-12043 Valve, Vacuum $124.80
90910-12079 Valve, Vacuum $160.00

*1996 FZJ80

I'm happy to order up from anyone on here that knows which is which. CDAN...???

After enough wading thru old threads, I found it posted by none other than Beno/Onur:

90910-12079

email sent.

Cheers!

 

[b16]

Funny, I had fixed my P0401 code by clearing one of the vacuum ports in the throttle body, went to Tahoe in the snow and somehow the other throttle body port got clogged. Tried to clear it with the same method I did on the other port (compressed air) but that didn't cut it. Thinking I have to remove the TB and really clean it.

Mine is also intermittent now, was regular for a while. Comes and goes. First you should make sure all your ports into the intake are cleared. Testing the VSV is also pretty easy.

 

[Chris Wilcox]

My vsv failed but only when hot. I replaced with new and moved it out from under the intake manifold (using a really long extension from under truck so I didn't have to remove manifold) to a cooler location by the drivers fender. Been daily driven and fixed since late 2008.