fourstars

This is a SWAP engine to a Toyota truck. But I would assume it’s the same troubleshooting techniques. Motor starts, idles fine, and revs strong. There is no hesitation or stalls. I have not driven it yet due to custom drive shafts. Here are the DTC:

DTC = 29 – Sub Rear O2 sensor
DTC = 31 - TPS
DTC = 41 – AFM

When I start the motor the check engine light comes on right away. Almost seems like the ECU is not recognizing these sensors. I have replaced the AFM with a working “used” unit and I get the same DTC. The TRAC control ECU with wirings has been deleted, there are “NO” DTC for TRAC. But the actuator and SUB TPS are present.

I have checked the 5v on all of the SUB/MAIN TPS and AFM and it is good. I also perform a continuity test with all the wires back to the ECU, everything checked out good. On the O2 sensor I switched it with the “L” side O2 and I also get the same DTC 29 code.. Im lead to believe there is an issue on the passenger side of the engine. Since the AFM, REAR “R” SUB O2, and TPS is in that area.

Funny thing is that when I check “continuity” with the wire that supply the 5v on the SUB TPS, Main TPS, and AFM (wire color Blue & RED) with any ground on the frame, I get a “single beep”.. On my Fluke 76, a single beep represents low continuity below 20 OHMS. I traced that wire and with the ECU ground to the ECU’s male pins (continuity with pin E2 & VC / VTA2) and I get the same single beep. NOT sure if this is normal.

My questions:

Are there any relationships between these 3 sensors that Im overlooking?

Is the single beep issue a normal operation of the ECU when the 5v wire is a hot wire?

Is there any other trouble shooting methods anyone can recommend before I switched out the ECU?

Thanks in advance guys.

Vrank

iTrader: (4)

Why you bringing vta2 in the mix? That's sub tps, or trac. Not needed here. Vta1 is applicable here. You kinda lost me describing beeps and stuff, as that doesn't really matter. What does matter is that vc is the name of your 5v reference, the blue/red stripe wire.

So are you saying you're checking your 5v reference for continuity to ground and it has it? Because that's wrong if it does.

So do you have the sub o2 hooked up? The one post cat converter?

E2 is your ground, supplied by the ecu, for all your 5v sensors.

fourstars

Sorry for the detail explanation man. Im just extremely frustrated. Thank you for your quick reply.

And yes, when check continuity for the 5v reference with ground I get a beep. I traced it to the MALE pins on the ECU "E2" and the MALE pin on the ecu for the blue and red wire and I get the same beep there as well..

Yes ALL 4 O2 sensors are hooked up.

Yes, E2 is the filter ground from the ECU.

Vrank

iTrader: (4)

Haha youre neridier than me. cool, because im gonna learn something here probably. Okay, so I'm guessing you're getting that because the key is on and the other sensors are plugged in and making their respective circuits to e2.

So what's the deal with vta2? Also, assuming this came from a donor sc, so engine/maf/ecu are correct, and this is obd1?

Did you actually go through the harness? Or did you just route power/chassis clutter in the truck to where it needs to be? You said wiring removed for unneeded circuits iirc, so maybe something over there is not right like you suggested.

It's worth popping the ecu open just for shots and giggles, take you 5 minutes.

fourstars

VTA2 is the only relatioship between Sub TPS, Main TPS, & AFM. That pin VTA2 is also the 5V reference, if not the VC pin is also in connection!

Yes, I bought a completely running 92 SC400 and transfer everything from motor, drivetrain, exhaust, etc.. over to my truck!

I did not splice the wire harness! I need all the sensors to pass California State BAR & Smog! So I deleted the TRAC, ABS, & Cruise controls! There are no DTC for those systems!

Wiring the motor to the truck was just like u said, routed power wire from harness, added a few relays & fuses and connect that with te body harness! Everything inside works and all the lights on my cluster operates like it should!

I have open the ECU and have looked inside! There are no white or green or any damages to any caps! It looks brand new with no dust and smells new!

Vrank

iTrader: (4)

Vta2 is the sub tps (trac butterfly) position signal line. Vc is your 5v reference and is the only relationship to the other sensors. Vta1 is signal for main tps, vta2 is signal for trac butterfly position. Vc goes to both, and so does e2 iirc.

If you didn't cut into the harness, then how did you eliminate trac stuff?

Bottom line, if you don't have the wiring going to the motor that operates the trac butterfly (large shielded cable in the harness), vta2 and the entire sub tps is not needed. It's worthless, and obviously doesn't throw the cel, so we need to get past that and eliminate it.

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Okay! So we are on the same page! Was trying not be too nerdy! Lol... Anyhow, What i did was de-pin everything and just remove the system. Yes i did cut the harness cover but everything was untounch besides TRAC. ABS, & Cruise Control. I also check my wiring diagrams and recheck each pin that was deleted.

fourstars

Im not sure how sensitive these motors are, but you think a body ground vs motor ground would make any differences? Passenger side ground bundle is mounted onto the body of the truck and NOT the rear of the valve cover as stated on the FSM.

Vrank

iTrader: (4)

It's worth trying, but I would think that if the engine is grounded well enough to the chassis it would be fine.

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Just got done troubleshooting with no success! I wired up a DLC2 Diagnostic Port to get live data but the scanner I have is not reading Toyota ports.. Running out of idea....

Vrank

iTrader: (4)

I'm thinking something is pinned wrong. From what you've said, that is the only variable here. You depinning and repinning. If it was working fine prior, that's all I can think of and the direction I'd look at. Are you sure vg isn't mixed up with vc?

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Thats what I had assume as well! But after multiple checking and reading wire diagrams, everything is connected properly! I know I did not touch the wires in quetion, these wire runs directly to the ECU. Unless the ECU is bad!

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****Funny thing is that when I check “continuity” with the wire that supply the 5v on the SUB TPS, Main TPS, and AFM (wire color Blue & RED) with any ground on the frame, I get a “single beep”.. On my Fluke 76, a single beep represents low continuity below 20 OHMS. I traced that wire and with the ECU ground to the ECU’s male pins (continuity with pin E2 & VC / VTA2) and I get the same single beep. NOT sure if this is normal. *****

Is this normal? Im assuming you have an SC400, if you can do a quick test to rule this out, then I would say the ECU is bad!!!

Vrank

iTrader: (4)

No, I had a couple, but only mess with JZ stuff now. Doesn't matter Toyota stuff from this era is all pretty similar.

If you deleted trac properly, you would not have vta2 in your harness. Again, why do you have Vta2 in your harness? Why do you have the sub tps still in the harness? It's only function is trac control. Since you removed that circuitry, sub tps along with vta2 shouldn't even be in your harness. At all. Why is it still there? Why? You should only be concerned with vta1. Did you accidentally remove the main tps instead?

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Both system sub and main tps was untouch! According to California State Bar & Smog, I can not have any unplug or hanging wires. By that i assume keeping the Sub TPS connected wouldnt be an issue! SUB TPS is connected to the ECU and is part of the TRAC "BUT" not part of the main wiring harness for the TRAC.