Configuration Resistors on 3VZ-FE ECU

[jon.sole]

Hi,

Has anyone played around with the configuration resistors on the 3VZ-FE ECU circuit board? I haven't seen any information on the internet, so I thought I'd post what I've learnt so far...

On the back of the PCB with the CPUs on, there are 3 resistors that look like they are used to configure the behaviour of the ECU, in the photo below the resistors are marked in red (position of the fuel/ignition CPU marked in yellow).



Toyota made a number of variants of the 3VZ-FE ECU (M/T, A/T, EGR, non-EGR), I reckon that these resistors are used to enable/disable certain features.

What are these features? To be honest, I don't know for sure, but I was bored at lunchtime and had a play around.

Moving R753 over to R754 didn't seem to have much effect :icon_conf, maybe it disables EGR?

Undeterred, I reverted the change and tried moving R752 over to R751. Now this one did have an effect :hehe: Taking into account that the 3VZ-FE is still in a Camry, I noticed that the idle now drops when drive or reverse is selected. Before the ECU would compensate for the additional load of the auto box, the idle would stay at 750rpm before the resistor change, now it drops to 500rpm. Also gears changes by the auto box are harsher, as if the ECU isn't bothering to retard the timing when the auto box changes gear!

Could this be the key to getting the ECU working with the manual gear box?
Unfortunately I don't have a V6 MR2 to test the idea, any one up for giving it a go?

The 7M-GE ECU can also be configured by modifying some resistors, for anyone interested, pop over to http://www.supramania.com/forums/showthread.php?t=73379, the guys there have been reverse engineering the ECU.

Cheers,
Jon

[Marksman]

Now that is interesting stuff. If nobody else volunteers we might be able to help in a few days :thumbsup:

Owen.

[Marksman]

Oh, and anybody got a manual ECU to open up and compare to? I was presuming a different firmware flash rather than just a hardware configuration but if not then that's a huge bonus!

Owen.

[jon.sole]

I'm guessing that the M/T ECU will have a load of components not fitted to the PCB as well as the configuration resistor changes.

I doubt Toyota would go to the extra cost of designing two separate ECUs (3 if you include the non-EGR versions in Japan), with different CPUs when they can use the same chip with the same SW in ROM and change it's behaviour with a few cheap resistors.

Of course I could be completely wrong! :blush:

[Marksman]

Of course I could be completely wrong! :blush:

I would prefer it if you could be right on this occasion. We have a recently finished V6 MR2 in the workshop (Paff's) and a couple of ECU's too but they're owned by other people who may be willing to help. Before we start we have a rough idle to eliminate so that'll take a day or maybe 2, hopefully just a leak of an ignition component. After that if nobody else has helped I'm sure we can have a look. We also have modified and virgin idle up valves so we could see if this fixes that issue at the same time :thumbsup:

Owen.

[Barronmr]

Hey, jon.

Where abouts in the country are you? I'd be willing to guinea pig 1 of my v6's when I get either of the blighter's fixed. Also got a spare ecu kicking about.

Regards Luke

[biteme]

I'd be happy to help as well in any way I can :)

[erol]

Hey Jon,

where abouts are you mate?
I would be willing to loan you my car if you promise I get it back running?

Erol

[jon.sole]

Thanks for the offers guys, I'm in Cambridge. If anyone's passing close by then we could try the mod.

Actually if anyone's confident with a soldering iron themselves, it only takes a few minutes to move the resistor over. Take the front cover off the ECU and the resistors are right there, couldn't be any more convenient!

To fully test if this mod actually runs the ECU in M/T mode, it would need an unmodified idle control valve and wiring with SP1 hooked up to the speed signal rather than the usual 5v workaround.

If I get a chance this weekend, I'll try and check if the first resistor actually does disable EGR, there's also the question of what the 3rd resister does, I haven't tried that one yet!

Cheers,
Jon

[OlberJ]

Nice find mate.

If this was a week ago i'd have gonme out and done it on the Mk1.6 i've got sitting there. Not sure if we've got any spare ECU's at work to try this and can't fuck with that one as it's now property of someone else. Bugger.