Wiring vh45 auto without speed signal

[RichZilla]

I'm in a real hurry to get the Merc on the road. All I really need to do to make it driveable is fab exhaust manifolds and exhaust and finish wiring the auto up - pretty much power wires and the wires that run from the AT ECU to the ECCS ECU. What happens if I have no speed signal from the dash? Is it like the 1UZ where it goes into limp mode and will only take off in 3rd unless you force it into a lower gear using the shifter?

I don't want to have to spend time trying to work out a speed signal converter/divider.

[zehnder]

Hey Rich,I to, am planning to use the AT and AT`s ECU that was mated to the VH out of the Q. You mentioned "speed signal from dash" and I was wondering if by this you mean a component in the instrmt. cluster. I saved the cluster out of the Q when I stripped out what I thought I needed. Does the AT ECU need a component from the cluster to operate properly? Could I remove and incorp. it to make the trans work like factory?

[RichZilla]

What happens is that the speed signal comes from the auto and goes to the speedo in the instrument cluster. The instrument cluster then sends the speed signal to the ECU. My problem is that I don't know what sort of signal the ECU wants to see. On a Lexus V8, the dash divides the signal by 5 and then sends it to the ECU. Normally we make a pulse divider to get around using the 1UZ dash.

I guess I'll soon find out.

[tmorgan4]

That's really the problem with this engine setup, as you already seem to know. You're really just going into uncharted territory. Hopefully soon we will know exactly how the engine works in these situations. Please keep me updated as I was curious about the same exact issue myself.

[RichZilla]

Will do. I made the driver's side manifold yesterday and what a bastard that was. Hopefully by next week I'll have the exhaust and auto power wires hooked up and we'll see what happens. I do have the Jaycar speedo corrector kit there ready to assemble if I have dramas. The kit also converts to different types of signals.

[tmorgan4]

What has everyone else done who is running this engine? I've got a speed signal wire coming from my dash but I can't imagine it's going to be a good signal for this ECU. I've done some searching and can't seem to find much info on this at all.

It would be nice to know whether the ECU does go into "limp mode" without this signal hooked up. Maybe we can get in contact with the guy doing the ECU programming. I read some of his posts and he's extremely familiar with all of the maps.

I just sent him an email. Hopefully I'll either hear back in an email or I gave him this thread address.

Now that I re-read this thread, are you thinking that only the AT transmission will be affected by a lack of or incorrect speed signal? I was under the impression that when the engine goes into limp mode that the engine RPM was limited too.
Modified by tmorgan4 at 9:52 PM 10/20/2007

[gs14racer]

The ecu runs fine with out a speed signal to the ecu, I dont even have one connected to the ecu on my car. I have run a few automatic nissans with out speed signals and they have ran fine but on the VH I can guarantte. I wouldnt think it would matter though.

[tmorgan4]

Sweet man...one more wire I can rip out of the wiring harness.

[zehnder]

Hey TMorgan ,Can we ask everyone to use wire color and/or description if it is an infiniti component to make what we are talking about easier to locate. It looks like GS Racer has a custom wiring job, which makes it almost impossible using his photo essay, to see what is all going on. Gs Racer, are you going to write up your sweet job up? I hate pestering you but would really love to see a written description of your work! I have FSM and everything on this site I have read, but still haven`t quite grasped what is essential and what is not.

[tmorgan4]

I too would like to see a full write-up put together so we can solve the wiring battle once and for all. The biggest issue with this is that the wiring colors and locations don't stay consistent throughout the various years. Even if you had to figure out a few wires that were different it would still make things much easier than starting off from scratch.

I am pretty damn confident that I have my wiring almost ready to go. I'd do a write-up right now but I'd hate to tell people how to do their wiring before I've even tried mine and verified that everything works correctly (or that the engine even starts!!!). I really hope to have my engine done in a month or so.

[gs14racer]

Im working on it guys I have just been busy lately, Ill be building a complete engine harness very soon so look out for that.

[qsiguy]

tmorgan4 sent me an email asking about the VH ECU speed sensor. Sounds like gs14racer answered it though. Since I have a Q45 I haven't had to check into that but I can certainly do some tests if you guys need something checked. I just got my turbo installed and have been working on the ECU programming and have access to most of the ECU and TCU wiring as I still have many interior panels removed.

Let me know if you guys need to know what voltage or signal is on a given circuit. I can check it out. I have the consult cable/adapter, laptop programs, EPROM programmer, oscilloscope, etc. I should be able to figure out anything you guys need info on in regards to wiring. Not sure what model you guys got your motors/ECUs/harnesses from but I have a 1994 model w/TCS as well as a '94 Q45a model that has a JWT Nos ECU.

[tmorgan4]

Thanks for posting over here Shane...you're going to be a ton of help with this wiring battle!

Do you happen to have any suggestions as far as hooking a tach up? I heard from some people that the Q45 ecu actually adjusts the voltage (as the FSM says) to the tach as the speed changes however my Pathfinder's ECU changes frequency, which "appears" to be a higher voltage. I'm not an expert by any means with electrical and in fact I don't understand much of it at all!

[qsiguy]

I wasn't aware of any differences with the Q's tach and other vehicles. Although the only thing I've ever done with a Q's tach is wire a remote engine starts signal lead to it and my Zietronics wideband O2 meter. I will look into that and do some tests as soon as I get a chance.

I know most tach signals are as you described. It is a pulse signal that shows up on a voltmeter as a certain voltage at various rpm's. As the pulses get closer together the voltage goes up. Anyway, I will check into it and post. I really don't think it's anything unusual though.

[tmorgan4]

Thanks Shane. I haven't been able to try it out which I know will be the easiest way to find out if it works or not. I just remember gs14racer saying that his tach didn't work, so I assumed something must be different with the Q45 tach signal or that maybe the tach in his vehicle is odd.