matt0922

I just purchased a 1995 4Runner and while I knew it had issues with 4WD when I bought it, I was hoping that it would be as simple as changing out a vacuum switching valve or something; after a little digging it gets more complicated, so here is my question;

1. Even though it is a 1995 it appears to have an older ECU (10-18-14 pin), along with a full engine swap of some sort (original and exchange both 4cyl); the current ECU in place is 89661-35160, and the truck is running fine, but when switched in 4wd the truck will die, and then will not restart, appartently due to the ecu being fried (the truck came with this story and two dead ecu's, one working ecu, all 35160) I'm thinking that the ecu that is in the truck is simply not correct for the engine that was swapped and somehow the 4wd fries it; my question would be how to identify what ecu I should be using, and if it makes any sense that it would fry the ecu.

I got a good deal on the truck, but I would like to use 4WD someday - any help would be much appreciated!

j2the-e

Looks like that ecu is for 1989-1990 cal spec. Start comparing both wiring diagrams and see what is different. Some wires may need to be moved or removed

matt0922

I've compared some of the wiring now;

1. The wiring harness does not have a wire installed on the pin for the second oxygen sensor, for the second oxgen sensor heater, or the EGR valve, so engine/wiring harness appears to be from an even older 22RE, but still EFI, which I believe puts it at 87-88. This still doesn't answer the question of why engaging 4WD might damage the ECU - from what I can tell the 4WD pin on the ECU is the same - can someone help with a pinout on a 87-88 22RE ECU? What does this 4WD pin do?

j2the-e

Not sure when they started using rear o2 sensor. Probably 95 with obd2. So your 89-90 ecu shouldn't have a rear sensor at all. Is it an electrical issue when it stalls? Like as soon as you shift it stalls? If so, maybe disconnect everything electrical that has to do with 4wd and see what happens. Disconnect the wires to the 4wd indicator switch on the trans. Is your truck a manual trans and transfer? Front diff add or manual hubs?

matt0922

Well, I opened up the 89661-35160 ecu and you can see that it has a pin for OX2 and HT2 (suprised me too!) - so I'm assuming that the ECU I have was designed for a rear O2 sensor - as for the nature of the stall, I have not exactly confirmed it yet because I don't want to ruin the one good ecu that I have - I did however try the 'bad' ecu's and confirmed that they don't work, but interestingly enough the truck will intially start and run for about 2-3 seconds and then die (all three ecu's also have fault codes of 21 and 27, related to the missing rear O2 I believe). I am currently trying to get another ecu so I can try it and see what happens; I think disconnecting the assoiciated electronics may solve the issue, but I would like to have it working properly; I guess what I'm really wondering is what if any problems the ECU from an 88 22re, with and 88 22re engine might cause issue with the 95 4WD hardware on the truck? Specifically what feedback does the 4WD transfer case give the ECU, and did this change between 88 and 95?

Also, it is a 5 speed manual and manual transfer, with front diff add (no manual hubs)

j2the-e

Maybe for the indicator light on the dash or the add. Well I did some checking and cali trucks had a rear O2 sensor in 89. News to me. So my guess is you have a non-cali harness. Your best bet at this point might be to find a matching ecu and harness.

matt0922

I just purchased what I think should be a matching ECU on ebay (88 22re, 89661-35110), and maybe that will solve the problem; I'm just confused how 4WD drive would ruin an ECU considering that this pin looks to be the same, at least from what I can find.

Another question; If I dissconnect the wire going to the indicator on the 4WD transfer case, will this cause an issue with the add engaging the front diff?

j2the-e

I don't know how that system works. If you disconnect the transfer switch, I dont think it will lock the front. You could get rid of the ADD and go with manual hubs. Best option anyway in my opinion. Try the matching ecu and see what happens. All kinds of weird stuff can happen when you mismatch. You have 89 cali ecu, non-cali harness and engine and 95 everything else.