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Thank goodness I read and overanalyze everything! While searching for wiring tips and hints I ran across a couple references to mismatched harnesses and ECUs. It turns out that in 1999 Toyota changed the MAF sensor. It has the same connector and number of wires but the pins have changed. I had made the adjustment on the ECU plugs when I compared the EWDs BUT didn't change the MAF or the wiring at the MAF connector. If I keep my 1997 MAF I need to switch the ECU wiring back. If I use a 1999 MAF I will need to make the connector pins match the MAF itself. One of the wires has a lot of splices to other components so I need to make it right whichever way I go. I thought I had a complete air cleaner assembly but apparently I don't. It's probably smarter to pick up a complete 1999-2000 assembly.
Mentioned along with the MAF is that the TPS and/or the throttle body may also be incompatible. The 1997 4Runner all this came from had all the options plus auto trans and cruise control. I'm sure the throttle body has lots of attachments but I don't see a reason it won't work. The TPS appears the same and the wiring diagrams show identical pinouts.
There are a few wires I was going to recover from the original 3.0 harness but I may be able to use the ones on the 4Runner harness (Reverse from auto trans but connect to manual trans switch, 4WD from transfer case switch, etc.). I will likely need to change the connector at the end so it's about as much work either way. I am still really contemplating splitting the harness to remove all the unused pieces (after I see if I can reuse some that I thought I didn't need). It will allow me to trace all this stuff and verify that the wires are going where I think they are so I don't have another issue like the MAF. If I do that I should premptively wire the cruise control so it's easy to add later. Where does the cruise control ECU live? I am adding power windows and locks but they are after market and have their own wiring.
Dumb question... where/how does this harness connect to the fuse box? I purchased extended battery cables and an extended fuse box feed wire from ORS. I can see how those attach and a large ground but where's all the rest?
Short answer is the harness doesn't connect to the fuse box. The longer answer is it connects through the body connectors with a bunch of other connectors, splices, and systems in between. Have you extended the positive battery cable to the fuse box yet? I need to update my build thread this weekend, so I'll try to get my solution to the ground and power issues posted.
Yes, my mistake! All the power pretty much ends up at the ignition switch and then (I assume) travels across the dash to the body plugs. I bought battery cables from ORS and got a fuse box power wire with it so that's covered.
I completely disassembled the 93 harness and kept all the parts for the starter, transmission, front axle, A/C clutch, and transfer case. That's most of what went to IH1 and IH2 and I left the splices for the ECU so it will be easy to plug them in. No pinning of connectors at the actual components if I do it this way. I just need to tape the old harness to the new one where it goes through the bulkhead.
Got a complete Tacoma air box, air hose, resonators, and MAF so I don't have to sort out what works. Now I need to switch my MAF wiring back to 1999 specs. Of the 5 pins, 4 are different from 1997-1999. But I think I know why, that MAF is shared among car manufacturers so I assume whoever spec'd it first got their wiring choice.
I may be out of town all weekend so probably not much progress...
There's a few others you won't need. SEL1 and SEL2 are only used on the 3VZE ECUs, so that's another one or two you can salvage. Your year of 5VZE doesn't use the AC Idle-up valve, so there's two more. In case you haven't already counted them, the two AC pins (ACT and AC1) are not compatible between generations and cannot be connected, so that's two more. If all else fails, my 3.0 experienced rapid, self-disassembly, so I've got some spare 3.0 parts including most of the engine harness.
Patrick
False, AC1 is the idle up signal. When it receives a ground the computer will idle up for A/C function.
Run the 3.0 cruise system, just modify the ball on the cable to a "bar style" to fit the throttle body.
run the 99+ maf because it is cheaper to replace if it fails.
The early tacoma and T-100 used the older style emissions canisters so not all the EVAP and emission stuff was in the engine harness and possibly not even the rear o2 senors. They also had a 4 wire tps. The extra wire was an IDL circuit that was used for cruise control. The 4 wire sensors were different than 3 wire and you had to match the throttle body to the sensor. You can use either matching units though as not having the IDL wire won't throw codes.
Thanks! My truck didn't originally have cruise and I didn't get the cruise control parts from the 4Runner so I'll have to find something whenever I get to that point. I ordered a 1999 Tacoma air box, hose, and MAF sensor and got them already. I need to take a look at the pinouts to make sure everything is correct (originally I only changed the ECU pins to the correct spots but the MAF reorders the wires as well). The TPS is a 3 wire and the EWDs say they are the same pinouts in 1997 and 1999. The 1997 4Runner harness and 1999 Tacoma ECU both have two O2 sensors (I already have all the exhaust parts). This is the evap box that I got with the engine.
08-01-2017, 01:00 PM
