Any Toyota techs here? Wiring question.

[i6pwr]

For a 3rd Gen Highlander V6 non hybrid, what's involved in replacing the engine wiring harness? Our 2014 has some rodent damage so exploring options. Would this harness be in the engine bay only with a firewall coupler or does it have wires entering the passenger compartment? Can this be done in a day with being mechanically inclined?

Any large parts needed to be removed with gasket changes or simply just alot of loom clips and hard mounting points?

Dealer labor is just astronomically high @30hrs.

All input appreciated.

 

[OilStainedNapkin]

Just to make sure you get a response, I would cast a wider net and ask this same question on Highlander specific forums as well (if you haven’t already)

 

[i6pwr]

Just to make sure you get a response, I would cast a wider net and ask this same question on Highlander specific forums as well (if you haven’t already)

Yeah, plan to hit a few other forums. I have also searched this on Toyota forums and it doesn't get answered much. I have no idea what's involved but could be a cash cow given the silence...Who knows. No doubt it's involved but I have to question 30 hours.

 

[Timmastertech]

I have never seen a labor time for a wiring harness replacement, thats a job that usually is a clock hours job. IIRC on Highlander, the engine wiring harness disconnects under the dash and then gets pushed through the firewall, but it has been a few years since I have had the powertrain out of one. Never done a wiring harness alone on one, only removed when doing things like engine R&I. If it was in my shop I would assess the damage and probably repair what was there versus replacement and wrap with the Honda rodent resistant electrical tape.

 

[eljefino]

I'd look at the replacement you're considering installing, while it's still for sale, and see how they logically removed it from the vehicle. I only have a couple credible experiences, one being an Ecotec in a Cavalier, which had an obvious "engine harness" and "body harness." It says to me that they plugged that harness into all the sensors of a naked motor then lifted the whole shebang into the frame on my particular car.

 

[clinebarger]

I wouldn't expect it to take more than 10 hours...The cowl & wiper assembly would need removal along with the Upper Intake.

 

[clinebarger]

Engine R&R calls for 21.9 hours on a AWD model which includes removing the harness with the engine/transmission & transferring it to the new engine. The dealer pulled the 30 hour labor quote right out of their behind!!

 

[i6pwr]

I'd look at the replacement you're considering installing, while it's still for sale, and see how they logically removed it from the vehicle

The replacement would be a factory new harness.

I wouldn't expect it to take more than 10 hours...The cowl & wiper assembly would need removal along with the Upper Intake.

Yeah, I did peek around quite a bit and traced the loom all over the motor, I don't see half their rate and 10 seems logical doing it the first time and being overly careful.

Engine R&R calls for 21.9 hours on a AWD model which includes removing the harness with the engine/transmission & transferring it to the new engine. The dealer pulled the 30 hour labor quote right out of their behind!!

I agree.

 

[97prizm]

For a 3rd Gen Highlander V6 non hybrid, what's involved in replacing the engine wiring harness? Our 2014 has some rodent damage so exploring options. Would this harness be in the engine bay only with a firewall coupler or does it have wires entering the passenger compartment? Can this be done in a day with being mechanically inclined?

Any large parts needed to be removed with gasket changes or simply just alot of loom clips and hard mounting points?

Dealer labor is just astronomically high @30hrs.

All input appreciated.

Well the complete engine harness retails for $3200. It looks like Toyota of Nashua has a sale of 32% off. Might be worth a look.

 

[i6pwr]

The part I need is listing for about $1450.

Toyota part# 82121-OE180

For that part# I was quoted 30 hours by 3 dealerships.

 

[KrisZ]

Where is the damage and how many wires are involved? Perhaps it would be easier to fix the wiring instead of replacing the whole harness. If your soldering skills are good, it’s an option if the damaged wires are in a fairly easy to reach location.

 

[someonesomewhere]

Where is the damage and how many wires are involved? Perhaps it would be easier to fix the wiring instead of replacing the whole harness. If your soldering skills are good, it’s an option if the damaged wires are in a fairly easy to reach location.

I would also go this option. Or pull one from a scrapyard. $1450 for a wiring harness? Holy cow!

 

[Nukeman7]

Where is the damage and how many wires are involved? Perhaps it would be easier to fix the wiring instead of replacing the whole harness. If your soldering skills are good, it’s an option if the damaged wires are in a fairly easy to reach location.

They key is how extensive is the damage and whether it is accessible to be repaired instead of replacement. I have repaired rodent chewed wiring on six vehicles this year, including substantial underhood and undercarriage damage. The hardest job was on a Nissan Pathfinder with significant wiring and vacuum hose damage that took 3 hours to repair. If the OP decides to tackle the repair, the following tools will help simplify the task immensely.

 

[i6pwr]

Well the complete engine harness retails for $3200. It looks like Toyota of Nashua has a sale of 32% off. Might be worth a look.

Yeah, it doesn't look like all the wiring needs replacement, can't see any other damage than the one pigtail right now.

Where is the damage and how many wires are involved? Perhaps it would be easier to fix the wiring instead of replacing the whole harness. If your soldering skills are good, it’s an option if the damaged wires are in a fairly easy to reach location.

It appears to be the MAF/IAT harness, which is an easy fix. I'm not a fan of a spliced section of harness given sensitive mV parameters of the PCM but safe bet it would be fine. If the insurance will cover the harness then I might just roll with it.

They key is how extensive is the damage and whether it is accessible to be repaired instead of replacement. I have repaired rodent chewed wiring on six vehicles this year, including substantial underhood and undercarriage damage. The hardest job was on a Nissan Pathfinder with significant wiring and vacuum hose damage that took 3 hours to repair. If the OP decides to tackle the repair, the following tools will help simplify the task immensely.

View attachment 254421View attachment 254422
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Thanks for all that..much appreciated. I have a stash of Wirefy water proof connections and also some of those Haisstronica connectors which impressed me.

 

[eljefino]

MAF should give a digital signal which will break through the noise of an imperfect splice.

IAT may not be used as much as you think, depending on programming priority. I'd risk it. If the data is shared with the dashboard outside temp display you'd know if you had a problem.

 

[Nukeman7]

MAF should give a digital signal which will break through the noise of an imperfect splice.

IAT may not be used as much as you think, depending on programming priority. I'd risk it. If the data is shared with the dashboard outside temp display you'd know if you had a problem.

Completely agree with @eljefino's position above. I had to splice two MAF connectors and a IAT connector on two vehicles with the Haisstronica connectors. One of the MAF connectors was missing 4 inches of the wire loom, so I had to add a replacement wire piece with Haisstronica solder connectors on each end of both strands. Both cars work perfectly since the repairs were performed months ago, so I believe you will be fine with the spliced wires.

 

[i6pwr]

IAT may not be used as much as you think

The way I understand how a MAF device operates, is the IAT is as critical as the airflow sensor. The PCM calculates the "mass" of the air by the airflow and temp of the air, to determine proper density...the "mass" is then calculated.

I just don't like being ripped off at a dealer even though I'm only paying a deductible. $5K labor to replace an above-the-engine harness is absurd.

Maybe it's worst case but that wasnt the vibe I was receiving.

 

[Marcozi]

MAF should give a digital signal which will break through the noise of an imperfect splice.

IAT may not be used as much as you think, depending on programming priority. I'd risk it. If the data is shared with the dashboard outside temp display you'd know if you had a problem.

The MAF should send an analog signal to the engine computer. The computer converts it to digital. However, the length of the cable from the sensor to the computer is critical.

 

[i6pwr]

I believe you will be fine with the spliced wires

I agree, I had to splice a TB harness on a GM vehicle and that worked great for years. I guess the only issue I'm dealing with is the decision to simply replace the harness given the reasonable deductible. I don't want to personally, but being it's the significant others' vehicle, it appears she is fine with removing any doubt there could be other damage that hasn't shown it's face yet. We are waiting to see at least what the estimate says.

I mean the size of the nest was next-level, eminent domain takeover size nest. I was absolutely stunned at how quick this was accomplished, I had just checked the washer fluid level 2 nights prior and the engine bay was clean. The nest stretched from fuse box to RH strut tower, and the entire width and height between the radiator and engine from splash pan to top of engine, including the top of engine back to firewall. Easier to say there was hardly any visible engine components.

Under the top layer was twigs as well. We were lucky it didn't catch fire.

 

[eljefino]

The way I understand how a MAF device operates, is the IAT is as critical as the airflow sensor. The PCM calculates the "mass" of the air by the airflow and temp of the air, to determine proper density...the "mass" is then calculated.

I just don't like being ripped off at a dealer even though I'm only paying a deductible. $5K labor to replace an above-the-engine harness is absurd.

Maybe it's worst case but that wasnt the vibe I was receiving.

If I were making MAFs I'd program them to give the PCM a complete picture of the incoming air mass with as much processing done on board as possible, so it could be the most plug and play solution possible. Of course over 40 years of the technology I bet there are some bastardized versions meant to fit a round peg in a preexisting square hole.

Found this chart of MAF waveforms:
https://autoditex.com/page/maf-lab-scope-waveforms-68-1.html

The PCM probably also wants a raw temperature for other reasons, like knowing a cold start from IAT and coolant temp lining up within a few degrees.

Now a personal anecdote, I was changing a spindle on a 97 Taurus and had to "handle" the ABS wire. Traced it underneath the car to a hole in the floor and couldn't be bothered to figure out how to unplug it. So I spliced the wires to the new one, with ordinary heat shrink tubing and some wire loom to protect it. Worked fine, and those tone rings don't generate a huge signal.