Configuration Resistors on 3VZ-FE ECU

[jon.sole]

Something I noticed this evening, with the resistor fitted at R751 instead of R752, the auto-box changes up early, even with the accelerator peddle buried in the carpet.

So my guess is that the main ECU chip running with this resistor configuration isn't telling the auto ECU chip the throttle position, so the auto ECU has no idea to shift at redline rather then a more leisurely 4000 rpm! Alternatively I could have damaged the auto box forcing it to do gear changes under full engine load :cry:

I'll try moving R756 over to R755 this weekend, so the configuration matches ThreeD's M/T ECU. But I'm putting it back to the original configuration before Monday. It's no fun driving with low idle when drive or reverse is selected, bits of interior trim are starting to rattle! The gear changes are making the whole car shudder and I can't even accelerate to redline :violin:

Cheers,
Jon

[Fizzy]

Something I noticed this evening, with the resistor fitted at R751 instead of R752, the auto-box changes up early, even with the accelerator peddle buried in the carpet.

So my guess is that the main ECU chip running with this resistor configuration isn't telling the auto ECU chip the throttle position, so the auto ECU has no idea to shift at redline rather then a more leisurely 4000 rpm! Alternatively I could have damaged the auto box forcing it to do gear changes under full engine load :cry:

I'll try moving R756 over to R755 this weekend, so the configuration matches ThreeD's M/T ECU. But I'm putting it back to the original configuration before Monday. It's no fun driving with low idle when drive or reverse is selected, bits of interior trim are starting to rattle! The gear changes are making the whole car shudder and I can't even accelerate to redline :violin:

Cheers,
Jon

Hmm.... if its manual mode with an auto box I guess the auto box would be in its easiest/lasiest settings (like a safe mode?), as it may well not be able to utilise any of the modes (performance, overdrive etc) as the autobox ecu isn't available. I would guess that the "kickdown" mode when you plant your foot is probably ecu controlled to an extent too? Thats assuming this resistor trick is essentially disabling the auto ecu/mappings......

This really need to be tested on an mr2 - if after changing the resistor on an mr2 the idle stays constantly at 500 then I guess its pocvip or throttle idle position adjustment time. :D

If only I had a spare ecu I would do the mod now... anybody nearby have one spare they can lend me? :fingersx: :wierd2:

Still wondering what the third resistor/option is for....

[Fizzy]

Just out of curiosity - has ThreeD's M/T ecu been used in an mr2? Just wondering if it has what the results were....

[jon.sole]

Hmm.... if its manual mode with an auto box I guess the auto box would be in its easiest/lasiest settings (like a safe mode?), as it may well not be able to utilise any of the modes (performance, overdrive etc) as the autobox ecu isn't available. I would guess that the "kickdown" mode when you plant your foot is probably ecu controlled to an extent too? Thats assuming this resistor trick is essentially disabling the auto ecu/mappings......

My guess is that in this 'manual' mode, the main fuel/ignition processor assumes the A/T processor isn't fitted, so the main processor doesn't listen to the retard ignition signal from the A/T processor. Normally the main processor would also pass throttle position information to the A/T which it uses to determine the shift points. In this 'manual mode' this doesn't happen so the A/T processor is working in isolation, all it can see is the gear box rotation speed via SPD2.

Still wondering what the third resistor/option is for....

Either the first resistor or the third must be to enable/disable EGR, we know that in Japan the 3VZ-FE didn't have EGR fitted, also it's been proven by disassembling the 7M-GE code that it uses a resistor to enable/disable EGR.

My guess is that the other resistor is to change maps for different octane fuel, but that's going to be hard to test without disassembling the ECU code or doing a dyno-run.

Cheers,
Jon

[Fizzy]

Interesting find for sure, also on the MT ecu two of the resistors are in different positions to the AT one, which would probably mean you are correct about their function.However (there's always one isn't there!) , i don't think the Mr2 Sp1 signal will work on either AT or MT ecu's (different from camry signal) so i think it will still throw a code 42, but it would certainly be interesting to try!

The one thing this might be useful for is an electrical fix for the v6 stall issue rather than the pocvip mod, excellent work :thumbsup:

Hmm... been thinking on this. I don't see why the speed signal wouldn't work as intended on an mr2. After all, the manual camry is using the same gearbox series as the mr2 - which probably uses the same speed sensor (given toyotas tendancy to re-use the same parts between models). As this goes to the dash and reads on the speedo in the same way as a camry, unless there's some unusual conversion going on there I would have though the same signal gets passed down to the ecu.

When the SP1 line was being utilised in the early days of the conversion and people were getting the hesitancy/timing retardation when it expected gear changes, where any 42 errors being logged then? If not then its most likely using the same speed signals...

...or am I just getting hopeful (and a bit off topic) here. :shifty:

[Fizzy]

Either the first resistor or the third must be to enable/disable EGR, we know that in Japan the 3VZ-FE didn't have EGR fitted, also it's been proven by disassembling the 7M-GE code that it uses a resistor to enable/disable EGR.

My guess is that the other resistor is to change maps for different octane fuel, but that's going to be hard to test without disassembling the ECU code or doing a dyno-run.

Cheers,
Jon

I would logically think that the first/topmost resistor pair is the EGR option, as that's the only one of the three in the same position on mine as in the M/T model shown earlier, and mine had all the EGR parts fitted on the donor engine (but were removed during install) - unless they were on but somehow disabled, which I think unlikely.

It makes sense that the ecu/car would behave a lot more erratically with an auto box on a manual ecu that the other way around - since the manual ecu obviously relies on you to do the hard bit. :mrgreen:

Looks like a switch needs to be wired in to each resistor pair to allow easy selection during testing. Any idea what value the resistors are, and if using a couple of discrete ones with wire and a three pole, two way (?) switch would mess up the signaling in the ecu at all - or is it pretty irrelevant since these are "option switches" rather than signal routes?

[jon.sole]

Looks like a switch needs to be wired in to each resistor pair to allow easy selection during testing. Any idea what value the resistors are, and if using a couple of discrete ones with wire and a three pole, two way (?) switch would mess up the signaling in the ecu at all - or is it pretty irrelevant since these are "option switches" rather than signal routes?

Each of the 3 options is connected either to 5v or 0v via a 1K resistor. I've traced other side of the resistors to input pins on the processor. It should be pretty easy to wire up some switches to set the options, the resistor values aren't that important, I measured two of the resistors at 950 ohms, the other was about 650 ohms even though they're all marked the same.

I also tried the 3rd resistor in the other position today, didn't have any noticeable effect :icon_conf

[Fizzy]

Each of the 3 options is connected either to 5v or 0v via a 1K resistor. I've traced other side of the resistors to input pins on the processor. It should be pretty easy to wire up some switches to set the options, the resistor values aren't that important, I measured two of the resistors at 950 ohms, the other was about 650 ohms even though they're all marked the same.

I also tried the 3rd resistor in the other position today, didn't have any noticeable effect :icon_conf

Decided to bite the bullet and have a go on mine.

First thing I noticed - the surface mounted resistor I removed from R752 is actually reading as 10k ohms on my meter. Checked the others and they seem the same?

I biult a small circuit using a bit of breadboard/prototype board and a jumper (rather than a switch). Soldered two 1K ohm ones on there. May remove those and put either 10k ones on or variable ones.

......and then got some wierd readings so I scrapped that and just moved the resistor.. rotflmao

[OlberJ]

and, any difference? or u not driven it yet?

[Fizzy]

Well - I put the ecu back in with the mod, and set my SP switch to "dash" so its getting the speed as normal.

Started the car - and it went up to almost 2.5k rpm.. 8O

but then started to go down. Settled around 1.2k rpm, so I took it for a quick spin - and there was no hesitancy at 2.5k, or 4k... :D

Got back and idle was at 1k rpm.... then dropped to 900..... and then stepped down to 800.....but then stepped back up to 900 and stayed there. I guess its learning the correct idle?

Switched off, and then back on and it went to 1.2k idle but then settled down to 900 again.

Soooo... looking promising! Will keep an eye on it next couple of days to see how things go. :shifty: