ECMs and Earths/Grounds

The 1UZFE EGR Delete Kit is available for sale here.


In building a new engine harness, what's the best way to deal with the numerous GNDs connecting to the ECM?

On my 3UZ (6-speed) ECM:

B2 (EC Chassis GND)
C1 (E02 RHS cylinder head GND)
C2 (E01 RHS cylinder head GND)
D4 (ME01 RHS cylinder head GND)
D6 (E03 LHS cylinder head GND)
D28 (E2 sensor GND)
E7 (E1 LHS cylinder head GND)

(Did I miss any?!?)

Apart from D28, all the GNDs effectively connect to the chassis somewhere, so where do people connect them? I was planning to connect B2 to an M6 terminal screwed into an M6 RivNut riveted into the chassis near the ECM (which is going to be under the dashboard in my conversion).

Based on the Lexus EWD, I also have E7 connecting to the same point as B2, and the other GNDs simply go from the ECM to the cylinder heads, but is that right? Any advice would be appreciated!


I'm not sure I would use a rivnut as a ground.

I'd rather use a stud screwed into a captive welded nut or a nut and bolt. I'd also ensure there was bare metal under the ground strap.

As for engine grounds, just do it as the factory did. They probably know what's best.
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Thanks, Rod.

I hadn't realised the rivnut/ground issue; it seems there is a wide difference of opinion on this use of rivnuts (judging from various forums). I always make sure the surfaces (inside and out) are free of paint, and I use knurled and serrated stainless steel rivnuts to get the most secure contact with the chassis. Flush-mount rivnuts would probably be best for this application, however, as that way the ground strap's contact would be directly with the chassis, rather than with the rivnut.

At this point I don't even have the donor car, much less the donor car's engine wiring harness, so I don't know what the factory did if it's not shown in the EWD. If there's no generally accepted custom wiring harness method, I may just buy an eBay engine harness in the meantime, so I can continue my advance planning with better knowledge of what the factory had done originally.


The factory uses quite a few engine based ground points. Do it just as the factory has and you shouldn't have any issues.

These engines aren't hard to get running in a different vehcile.

I've been driving a swapped 1UZ in various guises for almost 20 years. I haven't been stranded on the roadside yet.