Truck Tech



Hi Roger;

I just (today) replaced my O2 sensor as trouble codes 21,26, & 27 were appearing when I did the diagnostic as described on this page:

After replacing it with a NTK OEM replacement from Napa, 26 and 27 disappeared but I am still getting 21. I pulled the EFI fuse out to reset the trouble codes. Any idea why error code 21 would still be appearing?  1990 Toyota P/U V6 4WD EXT Cab DLX

·        RiderDre


Hi RiderDre;

How about the 2nd possible cause listed for #21:


You could check for the presence of the O2 sensor signal at the ECU itself.  It’s not uncommon for the O2 sensor wiring to fall against the exhaust manifold, the insulation melts and you get a short.

·        Roger


[A reply from RiderDre]

Hi Roger;

Ok I just looked at the wiring and it’s trashed. It must have been hanging on the exhaust as you can tell its burnt right through. I’ll try soldering it back together and taping it up and positioning it better today and let you know how it goes.

·        RiderDre



Hi Roger;

I would like to run 1983 rear springs in the front of my 85 runner, and I was wondering if my stock front shackles would work, or if they are too short, and would bind the spring under compression.  I am reluctant to go with 2” longer shackles, as I don’t want too much lift and/or bad pinion angle.  Do you think 1” longer shackles would work? (I was looking at Sky’s boomerangs, they look like a cool idea, but they are 2”, according to his site)  I hope my question made sense, and if you have any observations....

I am running Old Man Emu 099’s now, with my perches drilled 1.5”, but the 35” Krawlers still rub, so I need to go forward with the axle some more. It seems like rears up front would be the answer.  For the rears I have been using the Mazda/toy hybrid packs, they are sweet! (And so is my UMHW 1” body lift)

Thanks for everything, Ed

Hi Ed;

I found I needed 2” longer shackles to handle the 2” longer springs.  That is a basic rule of thumb I discovered when dealing with longer than stock springs, add 1” of shackle length for each additional inch of spring length in order to maintain reasonable shackle angle.  That is unless you plan on moving the front hangers forward an inch or two, you will need longer shackles.  Note that you will likely get very little lift from the longer shackles up front.  In my case, I lengthened my front shackles 1.5” and observed no lift at all.  I describe the issues in more detail on my web page:

·        Roger



Hey Roger;

I have an ‘86 4Runner and I’m trying to find out what the towing capacity is - any idea?  Also, I can’t seem to find a hitch - any suggestions?

Thanks; Layne

Hi Layne;

Per my 1985 4Runner Owner’s Manual:

2000 lb. trailer + cargo weight

Total weight of vehicle + trailer + cargo under 5500 lbs.

Toyota makes (or used to make) a rear hitch.  Many after market rear bumpers offer hitch receivers.  Or, search the web, I used Google to search for “hitch receiver” and on the first listing, found this:

·        Roger



Hello Roger;

I just read your article about Toyota 4-Runner rear power window problems. I was wondering if I can get your opinion on the particular issue that I am having with my 89 Runner.  The rear window motor and front console switch work perfectly, but the rear key switch will not raise or lower the window.  There are three wires that go to the switch.  I think that one is the power, one raises the window and one lowers it.  With the ignition off I used a test light, and none of them carry a current.  I assume that one should, considering that the window should operate from the rear key switch with the ignition off.  I have tried applying power to all three of the wires and nothing happens.  Looking at the wiring diagram it seems like maybe the key switch gets power from somewhere in the relay assembly.  I should also add that when I tool the panel off someone had spliced the tree wires going to the switch, and left them exposed.  I am wondering if one of them touched the body and caused a short.   I am not that good with electronics, so short of replacing all 4 of the relays I have no idea what to do next.  Any advice that you can offer would be greatly appreciated.  Thanks for your time; John Camp

Hi John;

None of those wires go directly to power, common side is grounded via the interlock switches, up and down wires go to the relay.  Check continuity (with an ohm meter or test light) from the switch to the relay module, using the wiring diagram at:

·        Roger


[a reply from John]

You will have to forgive me, I am pretty illiterate when it comes to electronics.  By what you suggested do you mean plug everything up, turn the key and test the up and down wires for voltage.  If they carry voltage would that mean that it is a relay problem?

·        John


Hi John;

I would disconnect the key switch and stick one wire of the ohm meter into one of the plugs then stick the other end into the corresponding connector pin at the relay socket and see if I got 0 ohms (i.e. continuity) between the two.  For example, if I plug the meter between the “D” connector of the “Back Door Control Switch” switch and #11 pin of the relay module connector, I should see 0 ohms, meaning the wire and connections are good.  Since that switch connects to ground, its unlikely you will measure much “voltage” at it, but if you have a current (or amp meter) hook it up between the switch connector and switch and see if “current” flows.  Or, just ground the “D” pin on the switch connector with a jumper wire, test light or current meter and see if that operates the relay.  One way to test a relay is to put a finger on it and operate the switch.  If you feel/hear the relay “click” but nothing else happens, the relay is getting power but the internal contacts are not making contact and switching power to the motor.  Normally the relay “click” is masked  by the sound of the motor running if everything is working right.

·        Roger




If you are searching for, building, modifying, or maintaining a Toyota 4WD mini-truck (Pickup, Hilux, 4Runner, Surf, or Tacoma), send your Truck Tech questions to Roger Brown at <>.  I’ll try to answer your questions with authority!