Toyota Tacoma Forum banner

2WD vs 4WD ECU

15K views 12 replies 4 participants last post by  Bvang12 
#1 ·
Hi Guys,

What is the difference between a M/T 2WD vs a M/T 4WD ECU??

I looked on the Toyota parts catalog and there are 2 ECU part numbers for my exact VIN Number for my 4WD. I'm in the process of getting a 2WD ECU for doing an aftermarket ECU install and using it for the box + connector. But if it will work I'll try that and see if my fuel consumption is lower. Just wondering if the fuel maps will be identical or if the 4WD will get a bit of extra fuel, which will then obviously not be an accurate test for my ECU swap to prove mine is faulty....

Also, does the transponder keys still work after an ECU swap? There is a Transponder computer on the parts catalog grouped with the keys and cylinder set which I presume will need replacement after the master keys are lost - no mention of the ECU. Anyone with experience?
 
#2 ·
Moving thread out of the Build section (where no one else can post to it) ...
 
#4 ·
A 4WD ECM will be configured to adapt to certain inputs or signals relating to four wheel drive being engaged. A 2WD ECM will operate 'blind' with respect to whether two or four wheels are being driven.

If you're talking four cylinders, the difference between 2WD and 4WD ECM's also involves the differences between two distinct engines (2RZ versus 3RZ) and the differences between the optimum 'logic' for controlling each of them.

I don't know for a fact, but I'd be willing to bet there are built-in fuel map / parameter differences between ECM's designed for a 2RZ versus a 3RZ. I have no idea if such obvious differences pertain to 6-cylinder models.

In your other thread:

http://www.customtacos.com/forum/29-maintenance/175178-2rz-erratic-vacuum-ign-advance.html

... you said this wasn't a Taco. If it's not a Tacoma, I can't tell you whether or not the remote keyless ECU is tied into the ECM (e.g., for locking down the engine). If the remote keyless ECU is independent of the ECM (as it would be in a pre-2005 Taco), swapping ECM's should have no effect on using the remote functions.
 
#5 · (Edited)
Yes.. Kind of confused as to exactly what you are working on .. But here's my experience. When the ECU went bad on my '97 2rz auto, I could't find a replacement..so I put in a '96 3rz box. Aside from a Ck eng.lite related to a vsv that didn't exist on the 97 it ran strong. A few months later I found a correct 2rz computer and put it in the truck..after a week, my brother swapped it out again because it ran better with the 3rz box and he didn't mind the eng.lite Something to note is that 95-00 49state emissions vehicles had different injector sizes for 2rz and 3rz..blue tops and brown tops respectively. 01-04 2rz and 3rz shared the same size injectors..the pink tops.
I'm almost certain when I was looking for a computer for my '02 2rz, the same pn ECU was listed for the 2rz and 3rz
As for immobilizer/transponder keys.. With earlier systems toyota said to replace keys and ecu as a set when all master keys were lost. Later they came out with an immobiliser reset function that requires dealership Techstream computer. Some locksmiths have different equipment that are able to put the ECM into a learn/reprogrammable Mode. Immobilizer was not available in the first gen Tacos to my knowledge. They did become available in the 05 models.
 
#6 ·
Yes - the immobilizer capability didn't arrive until the 2005 model year.
 
#7 ·
Here is some more info:

4WD and 2WD drive wiring is the same, so is the engine (on my Toyota thing)

So wiring should not be a problem I suspect only fueling *might* be different. ZIP, your test might be confirmation of this but unfortunately not the same engine.... I'm expecting a 2WD ECU later this week so will see what that part number is.

I did some more searching and it seems I will have to marry the Engine ECU and the Transponder ECU by "Registering a new ID" I have found that if you short pin 4 and pin 13 on OBD, the Key ECU and the Engine ECU exchange some nice words and decide to work together!

Link: mhhauto.com/Thread-toyota-immobiliser-code-reset-by-techstream

Another document said I should short CG (Chassis ground) and Tc (??) of DLC3

My problem is I only have the old engine bay diagnostic connector which does not have pin numbers only names and it does not have a Tc pin. My Key ECU is wired to OP1 of the diag connector, not sure if this is the same as Tc?

If I had a Toyota diagnostic connector cable to OBD adapter cable I would know what to short out but me not have one... Anyone have a pinout for these cables?
 
#8 · (Edited)
#9 ·
Thanks!

After I posted I also found that diagram but will have to confirm on my connector if that pin is indeed wired up.

Another thing I found was a Toyota OBD pin out, it turns out the Tc terminal on that connector is the "Timing Check" pin so this should be the same as the TE1/TE2 ( can't recall which one) pin on the diagnostic connector.

Suppose once I have the 2WD ECU I'll just have to try and see. I was worried that I might have to get the KEY computer and the ECU as a set but it looks like it should work by just replacing the ECU.
 
#10 ·
Another thing I found was a Toyota OBD pin out, it turns out the Tc terminal on that connector is the "Timing Check" pin so this should be the same as the TE1/TE2 ( can't recall which one) pin on the diagnostic connector.

.
To check timing on OBD1 vehicles, you jumper across the TE1 and E1 terminals to stabilize the timing (E1 being computer ground/Earth)


jumpering Tc and E1 will cause all the check lights on the dash to flash any codes that may be stored (SRS,ABS etc)
...so TE1 cannot be the same as Tc?
 
#11 ·
Zip I think we are talking past each other....

I think the Tc pin refers to the OBD2 plug pin name, not the firewall diagnostic connector pin.

I then made the conclusion that because I don't have a OBD2 plug and the Tc stands for Timing check, on a vendor specific pin, that maybe, just maybe, Tc on OBD2 is the same as my TE1 terminal on my connector. It is my best hope. Other ECU was only collected last night so I'll probably only get it by next week to confirm for sure.
 
#12 ·
ECU arrived today, 2WD, completely different partnumber than my 4WD.

Plugged it in, jumped TE1 and E1, switched ignition ON and waited 30 min, ignition OFF removed jumper. Car starts right up.

Took it for a drive, no difference! AFR was reading about 10.6 flying up a hill, engine was maybe a bit cold and received some enrichment. Got home ignition OFF, 4WD ECU plugged in, start car without using jumper for TE1 or waiting 30min....??

Took for a test drive, same routine AFR reading about 11.2 Got home switched OFF, tried other master key, starts right up.

So, with my simple test I can't feel any difference between 2WD and 4WD ECU - remember they were meant for the same engine - 2RZ-FE

Also, either both ECU's are now synced with the immobilizer or the immobilizer does not do the complicated stuff Toyota patents says it does! I should have tested the new ECU without the "communication ID reset" routine damn... Might explain why these vehicles were stolen so easily and often!
 
#13 ·
Hello Im thinking about getting a 2wd ecu for my 4x4 3rz how do you do this when you say plugged in and jump te1 and e1 do you get the pins and plug it in both of those at the say time on the obd reader please tell me and will i be able to drive 4wd withe this ecu
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top