Strange CTIS issue - could use some input

[Awesomeness]

Since I got the truck, my CTIS mostly works, but often flickers like SGTHoffer's video below, and sometimes goes 5-flashing (that shutting off the truck and restarting, as the manual says, seems to usually correct). I have a '97 M1078(A0), with the green CTIS controller. I've tried replacing it with to different used black (newer) CTIS controllers, which seem to work, but always blink "CTIS Overspeed" above about 35MPH. The original green controller (with the flickering issue) does not have the "CTIS Overspeed" issue.

It doesn't look like the TMs or updated Spicer troubleshooting guide address this. Did I just get two bad black CTIS controllers, or is there somewhere else I should start looking?

SGTHoffer's flickering post: https://www.steelsoldiers.com/showt...TIS-Question&p=2084935&viewfull=1#post2084935
https://www.youtube.com/watch?v=U2Zb9CQM_2o

 

[NV555]

Might be an issue with the manifold under the passenger kick out panel. The manifold has 2 parts air and electric.

There are several good threads on this issue.

 

[Awesomeness]

I've read through the prominent threads on it, and they didn't have much insight on this issue.

If it were the manifold, what would the theory about how it causes a CTIS overspeed be? That it's incorrectly reporting the pressure? And why only with the black controllers?

I've tried thinking through some of these things, trying to come up with a theory I could go test/replace something to prove right/wrong.

 

[Suprman]

The overspeed light comes on at different speeds depending on the pressure mode selected. Linked to trans control for speed info. Could be a connection issue where the harness meets the controller. Could be trans control or sensor related. Hard one to narrow down.

 

[DCLund]

My 96 1078 does the same thing "flashing overspeed" above 30 mph, but the system functions perfectly according to spec. 14 @emrg, 20 @mud/sand, 30@X/C. "Highway" above 30 flashes "over speed" but the pressure remains 55 psi at the tires.
Probably a bug from updates? I have the original WTEC II transmission controller but the truck had 25,000 miles. Must have had other updates. Maybe a different speed sensor? Sure like to know what changed.

 

[DCLund]

Just want to be clear. My system will automatically adjust up in all the lower settings as appropriate for overspeed. While in Hwy mode, reading overspeed above 30mph, it maintains 55 psi at the tires.
Hope I didn't confuse things

 

[Awesomeness]

My 96 1078 does the same thing "flashing overspeed" above 30 mph, but the system functions perfectly according to spec. 14 @emrg, 20 @mud/sand, 30@X/C. "Highway" above 30 flashes "over speed" but the pressure remains 55 psi at the tires.
Probably a bug from updates? I have the original WTEC II transmission controller but the truck had 25,000 miles. Must have had other updates. Maybe a different speed sensor? Sure like to know what changed.

Yes, that's what mine does, and only when the black controllers are plugged in. The original green controller doesn't have the overspeed problem (but does have the flickering problem, which is why I'd like to replace it). Do you have the black controller?

 

[319cssb]

@awesomeness : did you drive your truck for a few minutes with a speed between 40-45mph after changing to the black CTIS? Observe what the overspeed light does after you have driven the truck

 

[firefinder]

May be overstating the obvious, but has the ground be verified? My CTIS ECU connection cable has a separate wire and ground lug that attaches to one of the ECU mounting screws. I always start any electrical / RF troubleshooting issue by verifying connection to ground.

 

[Awesomeness]

@awesomeness : did you drive your truck for a few minutes with a speed between 40-45mph after changing to the black CTIS? Observe what the overspeed light does after you have driven the truck

Yes, I drove it around town for a while at various speeds up to 50MPH+. Sorry I wasn't clearer, that's what I was trying to say ("always blink "CTIS Overspeed" above about 35MPH").

May be overstating the obvious, but has the ground be verified? My CTIS ECU connection cable has a separate wire and ground lug that attaches to one of the ECU mounting screws. I always start any electrical / RF troubleshooting issue by verifying connection to ground.

Yes, I connected and checked that ground cable. If I put the green controller back in, it doesn't complain about "CTIS Overspeed", and only does when I reinstall either black controller. I've checked most of the obvious things I could think of (e.g. ground, cleaned the contacts, uninstalled and reinstalled each of the cables and controllers) and I get the same results (e.g. "CTIS Overspeed" when over 30-35MPH with the black controllers installed, not with the green).

I'm hoping somebody has an theory of what's happening, that would give me reason to check or replace something specific. For example, "There are two versions of the speed sensor, so maybe switch to the newer one that the black controllers would have had installed in an A1 truck". While it's possible I got two bad black controllers, as they were used, they seem to work well except for having the same "CTIS Overspeed" problem (e.g. they don't flash any warning lights or act strange, and they air up and down correctly).

 

[Suprman]

How does your trans shift? Cant hurt to replace the output speed sensor on the trans. Common over the counter allison part. Even if its not bad a new one seems to make trucks shift a bit nicer. Could be both ctis controllers have their own issues. Often a controller will work fine in one truck and act up in another truck.

 

[Awesomeness]

It shifts pretty hard, I've thought mostly because it was brand new. They were replacing the transmission in my truck when they put it up for auction - Allison tech found a ground wire that needed to be moved to a different pin in the connector, and then it started right up.

 

[Suprman]

Strange. Working in comm gear in the 90s we would make some of our own cables. The tm would tell you which connectors to use, what cable and the pinout. I find it hard to believe the army has field techs making up trans harnesses though. They all have their own assigned part numbers. So if someone was moving pins around when they really werent supposed to, all kinds of strange things could happen. Like an incorrect ctis speed warning. Cant hurt to swap the output speed sensor. If they are really bad you can get a jittery or incorrect speedo reading. Is your speedo smooth and basically correct?

 

[319cssb]

The black CTIS ECU will show the overspeed light until the truck is driven above 40-45mph for a few minutes. So that's not it.
The transmission output sensor not working right will cause the overspeed light as well.

 

[DCLund]

Yes, that's what mine does, and only when the black controllers are plugged in. The original green controller doesn't have the overspeed problem (but does have the flickering problem, which is why I'd like to replace it). Do you have the black controller?

Mine is the black controller. It functions perfectly other than the overspeed indicator above 30. I'm not sure if the speed sensor on the trans was ever changed.
I did have rough shifting when I bought it but that was cured with a new and calibrated throttle position sensor.

 

[scottmandu]

Looks like a faulty electrical connection.

 

[Awesomeness]

The connections obviously work (as far as "CTIS Overspeed" goes) while the green controller is in place, so it would be hard to support that a faulty connection existed anywhere other than the controller connector itself. I do assume the flickering in the old green controller is a faulty connection, probably internally since neither black controller flickers. So I don't think there is any clear evidence at this point that "a faulty electrical connection" is any more likely or unlikely than anything else (e.g. faulty component such as a speed sensor, getting two faulty used controllers, etc.).

Before this thread I hadn't previously heard that the black controllers had to be driven above 40-50MPH for several minutes in order to clear the "CTIS Overspeed". Can anyone cite a source of that information?

I do feel I've met that requirement already, as I drove it around ~10 miles with each of the controllers, but since it's an easy thing to test I'm going to try that one again. I'll drive it around longer and make sure I get a good 5+ minutes of over 40-50MPH in one highway drive, and then another 5+ minutes total above 40-50MPH amongst starts and stops.

 

[319cssb]

The connections obviously work (as far as "CTIS Overspeed" goes) while the green controller is in place, so it would be hard to support that a faulty connection existed anywhere other than the controller connector itself. I do assume the flickering in the old green controller is a faulty connection, probably internally since neither black controller flickers. So I don't think there is any clear evidence at this point that "a faulty electrical connection" is any more likely or unlikely than anything else (e.g. faulty component such as a speed sensor, getting two faulty used controllers, etc.).

Before this thread I hadn't previously heard that the black controllers had to be driven above 40-50MPH for several minutes in order to clear the "CTIS Overspeed". Can anyone cite a source of that information?

I do feel I've met that requirement already, as I drove it around ~10 miles with each of the controllers, but since it's an easy thing to test I'm going to try that one again. I'll drive it around longer and make sure I get a good 5+ minutes of over 40-50MPH in one highway drive, and then another 5+ minutes total above 40-50MPH amongst starts and stops.

Yes since I posted it , I can cite a source.
PS magazine 651 feb 07 page 14

 

[Awesomeness]

Thanks. The way I'm reading that, the overspeed isn't flashing because it was changed, it's just that the new black controller behaves differently with regard to the overspeed warning (namely, if you air way down the overspeed will begin flashing continuously, and even after reaching propper pressure it's still going to keep flashing until it's been driven fast for a little while). I was really hoping there was going to be more info in there.

 

[319cssb]

Thanks. The way I'm reading that, the overspeed isn't flashing because it was changed, it's just that the new black controller behaves differently with regard to the overspeed warning (namely, if you air way down the overspeed will begin flashing continuously, and even after reaching propper pressure it's still going to keep flashing until it's been driven fast for a little while). I was really hoping there was going to be more info in there.

Well , it's 100% more info on the subject than what you had before I posted about it. You can always take it from there and see if google has more to offer on this overspeed subject.