Engine ECU 4WD Signal

I'm working on doing a 5spd manual swap on my 2nd gen 2TR-FE (2.7L) auto. While trying to find an engine ECU from a manual, I noticed there is a differences between the ECU for a 2WD vs a 4WD. Interestingly, this is only the case for the 2TR-FE. The 4.0 uses the same ECU for 2WD and 4WD trucks. So I dug a little deeper:







What I found is that the engine ECU is getting a ground signal from the 4WD system. The 2.7L gets only a 4HI signal while the 4.0L gets an additional 4Low signal. The question is....what is it doing with this input? Is it changing the fuel mapping? Is it turning off traction control? What is the engine ECU doing with the knowledge that you're in 4WD?

 

The 4L signal is used for the A750F exclusively for torque converter lockup and also changes the shift points. The ADD sensor is also sent over the skid control ECU. The fuel mapping has nothing to do with it. If you are swapping to a manual, it does not really matter.

The ECM monitors the transfer-case L4 position switch to determine whether the transfer-case L4 gear is
engaged. If the transfer-case L4 gears remain engaged under the following conditions, the ECM
determines that there is a malfunction of the L4 position switch:
• L4 switch indicates that the L4 transfer-case gears are engaged.
• Transfer-case shifter is in the "H" position.
• Transfer-case output shaft rpm is between 1,000 and 3,000 rpm.
• The specified time period has elapsed.
If all of the above conditions are met, the ECM determines that there is a malfunction of the L4 switch,
illuminates the MIL and stores the DTC.

 

Interesting. Thanks for the info.

So what does it do with the 4WD signal?

The 2.7L has a manual has different ECMs for 2WD and 4WD trucks. So I’m guessing they are doing something that isn’t exclusive to the A750.

Also, where did you find this info? I’d like to review more stuff like this if it’s publicly available.

 

It's sent into the ECM then sent to the skid control ECM. Don't believe it does anything for the engine control that I could find. Since I swapped to the FJ manual ADD tube, my ADD sensor is left ungrounded and I have not noticed any ill effects. For some of the newer trucks, different versions of traction control are available in 4wd and 4lo, so that is where the sensors are used. The ECM is different for 2wd and 4wd due to using the transfer case signals as I mentioned above. The A340E does not need to know transfer position since there is no transfer case. In the case for the tacomas, the transmission control is integrated into the engine ECM, hence why there are two versions.

 

Yea, I mean that all makes sense. The only wrinkle is that we are talking about the R155 (manual) not the A340 (auto). So the ECM isn't controlling the transmission in this case. Additionally, there are two versions for the 4 cylinder (2WD/4WD), but only a single universal ECM for the V6 manual that covers both 2WD and 4WD.

 

you are just repeating what I already said. The manual wouldn't care about those positions, so it doesn't matter. A single ECM for a manual transmission regardless of 2WD or 4WD is just as I said, no input to manual transmission for shift points. I'm certain there would be two versions of the ECM for a 2WD and 4WD automatic V6, one for the A750E and one for A750F. If you convert a 4wd 4cyl to a manual, you can use either ECM, as the output of that ECM which inputs to the transmission is not used.

 

You're saying the opposite of what I'm saying. I'm saying this is only the case for the V6, not the I4. The I4 manual I believe has two difference options for the ECM. But as you pointed out, I don't think it matters for me. I'm just trying to more clearly understand what the ECM is doing so I can bypass any issues I run into.

 

I'm not sure what the concern is then. There would be nothing to bypass if converting to the R155F, and you'd keep the same ECM. Here are an example of the differences, it would also be changed because in 2009 Toyota switched to electronic traction control, so there are many variations of the ECMs

2.7L 4x2 AT - 8966104E92
2.7L 4x2 MT - 8966104E72
2.7L 4x4 MT - 8966104E82