3FE ECU Modifications

[73tlcv8]

I've recently put a 3FE in my 40 series truck. In the process I deleted the EGR and connected it to a H55F.

I was lurking on the Supra site where much work has been done on the 7MGE and 7MGTE ECUs. Apparently Toyota uses pull up/pull down resisters to tell the ECU processor if the vehicle has EGR or not and if has a manual or automatic transmission, at least on the late 80s 7MGE ECUs. Since the 3FE came out at the same time, I assume the design is similar.

There is a row of resistors R508 thru R502 in the 3FE ECU that tell the ECU if the truck has EGR and what trans it has (Inside red box in the picture). This ECU is for a US market truck that came with EGR and automatic transmission. I am trying to figure out how the resistors would be configured for a truck that came with no egr and/or a manual transmission from the factory.

Can someone with a 3FE ECU that came from the factory with a manual trans and no egr, if such a truck exists, tell us what resistors (R502 thru R508) are installed for that configuration. This, I would assume have to be a non US truck. Thanks very much.

 

[Spook50]

Unfortunately I don't think a factory non-EGR 3FE exists. Honestly I doubt you'd gain much by modifying the ECU on these vehicles, as the transmission has no electronic control, and from my own personal experience, properly removing the EGR already nets you a small improvement in mileage and maybe a slight performance improvement and that's it. The problem is that these engines really don't have much in the way of "untapped" power that can be taken advantage of. The best way to get the maximum available power would be to swap out the automatic tranny with a manual. The auto sucks up alot of available HP that wouldn't otherwise be lost when using a manual.

 

[73tlcv8]

If I wanted power, I would install a V8. Just experimenting.

 

[elripster]

Are you able to tell if the channel is a pull up or pull down? If so then you can probably assume it's a 5V channel and you want to flow less than say 50 mA. Then, V=IR can give you a resistance. In fact, if you can determine if the channels are pulled up or down which you should be able to do by checking the resistance on the resistor to a ground pin and/or 12V pin you can probably assume the resistors are either there or missing. That way a pulled high channel stays high and conversely a pulled low channel stays low unless the resistor is in place.

It is entirely possible different resistor values were used to cause the channels to float at or near a given voltage level but often these are simple Boolean channels that are high or low.

Frank

 

[ChaserFJ60]

Anyone look into this recently?

 

[Spook50]

Anyone look into this recently?

I've run without an EGR for just over 15 years, and there are no issues with simply removing the whole system. The ECU quickly accommodates however necessary for the missing EGR components whenever the battery (or EFI fuse) is disconnected for more than a few minutes, and that's it. I've never even gotten a CEL (though come to think of it, I'd have to double check and see if there are any CEL codes for our rigs that pertain to EGR. There might not be, but don't quote me on that since I don't have a book in hand).

Also since swapping my A440F for an H55F two years ago, no change whatsoever that affects the ECU. Like I had mentioned way back when this thread was originally started, there's no electronics in the tranny pertaining to the ECU, so I'm 100% confident that nothing would be gained by messing with these resistors.

 

[elripster]

I ran the 3FE with an H55 too and had zero issues.

To the original poster, you might take your meter and Ohm out the resistors to the corresponding pin. Note the resistance, even post up here. Then, plug in the ECU and measure the voltage at those pins. I am 99% sure that those are pull up channels that would be pulled to ground. If you see voltage on the pins that is confirmed. Then, experiment with pulling down the channels and see what changes.

Or, like Spook says, just install it and go. The system will trim fuel and timing accordingly to accommodate lack of EFR and simply doesn't care if it's controlling a transmission.

Frank

 

[1911]

Me three; deleted the EGR on my 3FE-equipped FJ80 and it ran good and always passed inspection ever after for as long as I and then my son owned it.

 

[Dynosoar]

There is a bypass plug (I will look and see if I have one and post a pic later) that was used on non California trucks for the EGR temp sensor. Basically bypassing the EGR. The 3FE does not seem to care and the o2 sensors will map the fuel accordingly. I have driven mine this way for 3 years and there are no codes or performance issues.
Dyno

 

[elripster]

Good point on the egr temp sensor, might need to jump that if you get the cel.