dei tach input signal.

Does anyone know exactly what the DEI tach signal wire expects as an input?

I ask because I, (like a few others) am having problems with the tach input of the remote start on a DEI alarm (Viper 5901).
I have a 2006 Ford E350 diesel van, that had the alarm installed by (what I thought) was a reputable dealer. The remote start has never worked right, and after going back 3 times to the installer to fix the problem, all they have seemed to do is hackup the stock wiring harness more each visit, broken more panel clips, drilled more holes in stupid places etc etc. I'm reluctant to take it back any more, as all they do is mess up more of the vehicle and installation.

After lot's or reading and searching, I have found 3 appropriate wires on the vehicle than can be used as a tach. (WHITE/ pink, GREEN / WHITE and another crank position censor GREEN/ black), all off the PCM. Each wire gives a perfectly normal tach reading, AC / DC depending on the wire. Both will pulse when the ignition is turned on, reset back to 0, then once started read depending on the revs.

But the alarm for some reason does not like this input, depending on the wire and how hot the vehicle engine is, it will do one of the following.
1) Turn ignition on & never even try to crank, repeat 3 times and fail.
2) Turn ignition on & never even try to crank, 2try it works.
3) Crank and start, but then shutdown and try to re-start, seems it doesn't think the engine is started.

I can understand #3 if it's a bad tach input signal, but I can not understand 1 & 2, since the tach input signal is always 0, why would it never even try to crank?

It seems that DEI have a module that will fix this, 454T. But that seems like a really hokey setup, strapping a box to the alternator wire looking for pulses. Seems the voltage remote start option option in the alarm should be able to do this, and that option doesn't work well either.

So, I'm trying to find out EXACTLY what the remote start tach input signal is expecting.

Thanks for any help.

Thanks. I have used the tach learn process, and use this each time I change the input wire. Tried it on both low and hi settings. It did not change the problem. But I have not tried setting the engine checking option to off.
Thanks, I will try that and report back.

t&t is correct as usual. Far from being hokey, the 454t is superb, saves any comeback from customers looking for a free tune-up, i.e.the "vehicle isn't running right any more" etc.etc. Doesn't interfere with the vehicle's wiring and works better, also unless you're from Oz, a Kiwi do you know what sheepshagger means?

Well, after playing with sending the alarm unit different voltages, what I found was that it actually wants to see a AC voltage of at least 25v constant on this tach wire before it will crank.
Obviously the tack wire on my E350 van is no good, since the voltage drops to zero after the key it turned on, but before the engine starts. It's a diesel, so you have to wait for the glow plugs to warm before cranking.

So searching for wires trying to find something I could use, I came across some unused wires, one of which it labeled CTS and is the same color (white / pink) as the tach wire from the PCM, but gives a very different voltage. Constant 33v AC and jumps higher ones started. Searching the net, CTS means Clean Tach Signal. So, I hooked it up and all is perfect.

Searching the net, shows on the F350 truck, these wires are by the hood release, and many alarm manuals list them as the wire to be used for the tach. But nothing mentions where they are on a E350 van. So anyone looking at this. They are under the hood, in the wiring loom that runs across the back of the engine bay. Just up and to the left of the water reservoir tucked in the end of the plastic tube the loom run in.

howie ll wrote:

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t&t is correct as usual. Far from being hokey, the 454t is superb, saves any comeback from customers looking for a free tune-up, i.e.the "vehicle isn't running right any more" etc.etc. Doesn't interfere with the vehicle's wiring and works better, also unless you're from Oz, a Kiwi do you know what sheepshagger means?

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Hawie, I disagree, but everyone has their own opinion. Below are the reasons for my comment on it being a hokey solution
A) A cheap and dirty way of overcoming a bad remote start circuit in the alarm.
B) More crap to go wrong.
C) More crap to sell the customer that he doesn't need.
D) Easier life for the installer, and the expense of the customer. (Sorry, had a bad experience with them so far).

I'm not from Oz, or a Kiwi and I know exactly what SheepShagger means, I also have a sense of humor

have you tried simply using Virtual Tach?   i have found it to be fairly reliable when proper tach cant be had....   this new Gen of units is very fussy about the tach reference... 50% of the time they dont learn tach the 1st time... of that 50%, 30% learn it if you change the tach threshold jumper to low....  of the remaining 20% i usually just use Virtual Tach....

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Kevin Gerry
Certified Electronics Technician
MECP First Class Installer

Owner/Installer
Classic Car Audio
since 1979

i have installed many of these alarms and in a couple of diesels too and i turn it to voltage and use the 15sec. wait to start function on the 5901. works perfect everytime.

Thanks for all the help. I tried both Voltage and Virtual tach, both worked but intermittently. Most of the time, it would start, but not realize it had started so shut off and try again after 5 or 10 seconds.
Seems virtual tach and voltage are very similar in that they both rely on voltage from the alternator to determine if the engine is running.

Once I found the CTO (sorry I labeled it CTS in my previous post) wire and cleaned up the installers mess it all works perfectly.
Here is a link to Ford's information on the wiring bundle I used, since it also has a speed signal and park signal I assume it would be useful for Stereo installs as well. This is for F series trucks and E series vans, with PTO option. (Standard on all Diesel & V10 gas models)
https://www.fleet.ford.com/truckbbas/non-html/2009/bb_pdf/336-337.pdf