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Discussion Starter · #1 · (Edited)
Hello, this is the 1st time I write a howto and this is not my thing 馃槄 english is also my secondary language, apologize.

What is the "high idle mod" or "Engine Coolant Temperature (ECT) mod"?

This mod is not really popular these days and I don't know why because it can be very useful and less expensive than an high output alternator...
It consists of putting engine in "open loop" by applying a greater resistance on the coolant temperature sensor, faking a cooler temperature so the engine revs at ~1500rpm instead of low idle.
There's some fire/work/military trucks that works like that, newer have integrated systems that tells alternator to crank it up while on parking break. I don't have the money for that and I don't have that need too. There's information for diesel trucks and stuff but not for the t4r so I wanted to have an up to date information.

some people used it for better A/C or a little more torque, to boost/jumpstart others, for winching etc. I had my compressor in mind and some winching in the future.

you can read more here ECT Mod

beware: I'm not responsible if you cut the wrong wire or mess up your ECM. Proceed at your own risks. I've read that it can cause alternator malfunctions due to higher temperatures but it was a thread about ambulances which runs 24/7.

Your dealer may decide to void any possible warranty even on floor mat. This is your choice to proceed.

stuff you need:
10mm socket (if you can find one)
wire cutter/stripper/crimper
potentiometer aka pot, I used 2k.
I used spade crimp connectors for the ease of "reversal"
I chose to add a relay and a switch so I can set it on/off remotely

1st step, you need to remove the glove box, I've followed this step by step

then unplug the B38 connector (2nd from the top on the ECM)

Organism Map World Mode of transport Slope
Automotive design Electrical wiring Cable Font Wire

Find the #17 pin, it's the green wire (on the lower side)

Rectangle Handwriting Font Office equipment Parallel

This is the point of no return. I used spade crimp connectors, so I can "revert" the mod.
Now you proceed at your own risks, cut the green wire #17.

I used a relay, the 87a goes to the ecm so it pass thru.
2k pot, pin 2 and 3 between relay's 87 and 87a

Electrical wiring Electrical supply Circuit component Cable Wire

then I wired the switch and voil脿!
start your engine, wait for it to heat up. Turn gently the pot clockwise untill you are satisfied with the idling speed.

any questions?

124 Posts
You do not mention your vehicle. 4Runner, what year and model ?

If your vehicle is still under warranty, not sure this is a good idea. May void the warranty.

5 Posts
Discussion Starter · #3 ·
In the 5th gen 4runner category, 5th gen 4runner.

I wrote that too "Your dealer may decide to void any possible warranty even on floor mat."
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