CTIS dash indicator solid

[jkcondrey]

I went through the TM for the ctis troubleshooter. I am having the ctis overspeed light come on while sitting. The setting is to hwy and all tires are inflated. As you move off, the light goes off on the dash, not sure what speed, seems to do it whenever. I have seen issues with it NOT coming on in the tm, but not the other way around. However, I've suddenly gotten a darty fuel gauge reading as well, so I am leaning towards a grounding issue. I did print off all 34 pages of electrical schematics, but to help speed me up, I wondered if there is a dash ground that I can look for to clean up, or are there going to be several grounds? My usual electrical work revolves around where the sparks fly, so it would be great to get a boost on where to look. Thanks anyone that can lend a quick tip.

 

[Ronmar]

The CTIS controller provides the overspeed light voltage directly to the panel light, so if the light is on it is the CTIS controller causing it.

Is your speedometer working/accurate? The CTIS controller shares the speed input from the transmission controller with the speedometer. Below a certain speed it should ignore the input/disable the overspeed light. If it was getting enough noise to think it is in motion, well then it would be doing its job but if the tires are properly inflated you should not be getting a light... Does the CTIS inflate to the proper pressure? If so then it is obviously capable of measuring the proper pressure. Does the overspeed light illuminate for an OS condition? Set mode to XCountry and drive at 40MPH. Light should illuminate, if you maintain this speed for 1 minute CTIS should re-inflate the tires...

I would check that the CTIS ground is attached under one of the mounting bolts, but this is kinda sounding like a CTIS controller issue...

 

[Suprman]

There is a separate sender in the tail of the trans that drives the speedometer separate from the output speed sensor. Looks like an old paddle key. If the 2 trans speed sensors dont jive together for some reason the ctis controller can show a false overspeed. Sometimes the controller can get confused and a drive will clear it up.

 

[jkcondrey]

The CTIS controller provides the overspeed light voltage directly to the panel light, so if the light is on it is the CTIS controller causing it.

Is your speedometer working/accurate? Does the CTIS inflate to the proper pressure? If so then it is obviously capable of measuring the proper pressure. Does the overspeed light illuminate for an OS condition? Set mode to XCountry and drive at 40MPH. Light should illuminate, if you maintain this speed for 1 minute CTIS should re-inflate the tires...

The speedometer appears to be working ,as I checked it with GPS, because try as a may, I cannot get this truck to run over 50 on a flat road, with no load. I have only had the controller set on hwy at any time. The hwy light will blink for a bit until air tanks are good, then it goes to a solid red light on the hwy button. I had never seen the dash indicator until the other day. And it was still set on hwy, with solid red light. I did not have a pressure gauge at that moment to check them, but none showed low visually, all up and looking normal. I will try the OS mode later today after work and see if it lights up for that.

Suprman: I had thought about changing out all the sensors on the trans anyways, I did have to replace the tps to get it mobile. I may go ahead and do the others now too. I was relating the issues(ctis light and darting fuel gauge ) to a ground issue, as they both started at the same time. However, I have also had an intermittent "stop, temp" light come and go as well. I used laser thermometer on that and ruled it out as engine and trans temps were good. I had hoped there was a cab ground that could be causing dash issues and not an entire harness problem.

 

[Suprman]

The output speed sensor on the bottom of the trans assembly you can find cheap like 69 bucks. The paddle one in the tail of the trans is around 800 bucks.

 

[Ronmar]

Superman where exactly is the sensor on the bottom of the trans? Got a P/N? Allison was a little confusing in their labeling of sensors in the trans. They called them speed sensors when it would have been more appropriate IMO to call them RPM sensors. in the trans would be a goofey place to measure vehicle speed...

At any rate the transmission controller only outputs one vehicle speed signal. On a WTEC II it is at PX33 pin H2 on the VIM, on a WTEC III it is P116 pin 30 on the transmission ECU. This vehicle speed signal goes to the speedometer connector PX8 pin4. It branches off at that connector and goes to the CTIS connector P110 pin U...
If the speedometer is accurately reflecting vehicle speed which he has confirmed by GPS then his vehicle speed signal is probably OK...

JkCondrey: Wont go over 50? What is the highest gear it shifts into? Have you checked for any transmission codes? When you replaced the TPS sensor, did you calibrate it?

 

[jkcondrey]

JkCondrey: Wont go over 50? What is the highest gear it shifts into? Have you checked for any transmission codes? When you replaced the TPS sensor, did you calibrate it?[/QUOTE]

It lists all 7 speeds and does shift into 7. I have done two cycles of the tps resetting(5 master on/off followed by a throttle pushing for idle and wide open), since I got the truck, mainly because of the lack of speed. I have adjusted the throttle linkage and the tps orientation per the manual as well. There are no codes currently. Prior to getting it, the issue was the tps and was showing codes for such. I replaced it, all was good, but just couldn't quite get up to that top speed. Its just weird that all these little gremlins popped up on one trip, that's why I was leaning toward a ground issue.
As for the speed again, I have only gotten over 50, downhill, on a long run once. I didn't get to take it the Denton show because I couldn't risk getting on the interstate for 2 hours at 45 tops.

 

[coachgeo]

...As for the speed again, I have only gotten over 50, downhill, on a long run once. I didn't get to take it the Denton show because I couldn't risk getting on the interstate for 2 hours at 45 tops.

check compression? check injectors? maybe your not running on all cylinders. Maybe an air leak into fuel that only appears at high vacuum thru fuel lines.... aka.... at high throttle?

 

[Suprman]

 

[Ronmar]

JkCondrey: Wont go over 50? What is the highest gear it shifts into? Have you checked for any transmission codes? When you replaced the TPS sensor, did you calibrate it?

It lists all 7 speeds and does shift into 7. I have done two cycles of the tps resetting(5 master on/off followed by a throttle pushing for idle and wide open), since I got the truck, mainly because of the lack of speed. I have adjusted the throttle linkage and the tps orientation per the manual as well. There are no codes currently. Prior to getting it, the issue was the tps and was showing codes for such. I replaced it, all was good, but just couldn't quite get up to that top speed. Its just weird that all these little gremlins popped up on one trip, that's why I was leaning toward a ground issue.
As for the speed again, I have only gotten over 50, downhill, on a long run once. I didn't get to take it the Denton show because I couldn't risk getting on the interstate for 2 hours at 45 tops.

OK, sounds like you are all over it Either you are severely HP limited as Coachgeo alluded to, or your governor is limiting your peak engine RPM. You need to tach the engine. Some digital voltmeters will read frequency. With one of these you could read the engine RPM sensor output either at the tach connector in the center dash or at the STE connector. Then it is just a little math(divide by ring gear tooth count) to get engine RPM. Or you can install a tach. This could be as simple as the maximum speed limit screw on top of the governor being mis-adjusted, but you need an accurate engine RPM measurement to adjust it. Oversped diesels tend to disassemble themselves...

 

[Ronmar]

View attachment 766201View attachment 766202

Yea, thats the one in the transfer case. I believe it is where vehicle speed is derived. I believe all the other sensors in the trans are used strictly for trans control...

 

[DCLund]

I had a few different electrical gremlins on my '96 AO. Marker lights and headlights flickered, trans shifted to neutral when the headlights were turned on and a few others. Some problems were constant, others appeared at random. In an effort to eliminate some basics I started with cleaning grounds and connections.
The connections I cleaned are:
Battery posts, Polarity Protection Box (PPB), Ground shunt (next to the PPB), PPB to starter, PPB to PDP (Power Distribution Panel) connections, PDP to body ground, Alternator to frame ground, and the cab to frame ground.
The last item, cab to frame ground seemed the most likely culprit. This is the heavy strap located behind the grill near the passenger side cab tilt hinge/mount. It was corroded and poorly assembled.
I couldn't say which one fixed what problem but my electrical system seems solid now. No flickers or voltage drops.
After all this my CTIS controller decided to brick itself (5 solid lights). Of course that was after teasing me for two weeks by working intermittently. I'm planning to go to manual CTIS control using electric over pneumatic. Eliminating unneeded electronics and circuits seems to be a good policy for me. Which reminds me I should also add that When I cleaned the connections at the Polarity Protection Box I decided to remove it from the system and splice the leads together. I am also replacing all the circuit breakers with standard automotive fuses, they're either good or they're bad and it's easy to tell.
Good luck

 

[coachgeo]

moderator please delete.... decided my post was too much of a thread hijack..... thanks

 

[jkcondrey]

Well the ctis overspeed went away. I did a cycle of airing down to xc and then back up. Then the next startup cycle the light did not return. Now of course I'm getting air venting out the front gladhand, so looks like I will be replacing those check valves like everyone else. I will still try to run it over 40 on the xc mode and see if it lights up. DClund, I am going to do the same thing, I feel like that has to be the main issue. I am also about to install a backup camera, so it would be a good time to check the box out and all the grounds as well.

As for the lack of power, I agree, it seems like it may be an air intrusion. I did have an issue with the primer pump back during winter, so I still think that its leaking. Ill try to track one of those down soon too.

 

[Ronmar]

Air intrusion is easy enough to look for. disconnect the return line at the tank and connect it to a clear hose and run it into the filler pipe. Then you can see any air.

Does your primer bulb get firm at all?

I did this video up A while back and just uploaded it to youtube last week. I think if you had an air leak big enough to cause running issues you would also have starting issues... primary fuel pressure is also easy to measure and could cause you issues...

Another place to look is exhaust temps. Using an IR thermometer, measure each cylinders temp on the ex manifold as close to the head as possible. I found a small difference on my #1 and #2 cylinders and when i pulled the valve cover found the timing adjustment for those two injectors was slightly off.

I think you should still measure actual RPM...

https://youtu.be/ZthRpf79gTg

 

[tennmogger]

Excellent video and well presented! Thanks.

 

[knelezen]

If you have a solid over speed light on the dash it means you have cycled the ignition 50 times with no speed sensor reading. Start the truck and drive it for a short distance. The light will go out when it detects speed.

 

[jkcondrey]

Air intrusion is easy enough to look for. disconnect the return line at the tank and connect it to a clear hose and run it into the filler pipe. Then you can see any air.

Does your primer bulb get firm at all?

It does start getting there after about 6 pumps. Another user mentioned the primer pump may be bad when I had a lot of starting issues with colder temps. Wes(simp) mentioned it when I picked up the truck too. I found the base for sale and will be ordering one this week to see if that alleviates the start problems. I may replace the fuel lines as well. It doesn't happen all the time, for example after it has been driven and warmed up, even the next morning, it'll fire right up no issues. But give it a day or more and itll smoke a good bit. My brother in law is a cummins mechanic but works on all kinds, I will probably have him do the up top work, injectors etc. I would really like to be able to get that top speed from it, most of the shows around here, and friends homes, are a couple hours away via interstates.