MTVR CTIS problem

[MAdams]

I've been trying to diagnose a non op CTIS system. I used the DANA software on my laptop and plugged into the computer. The software says that the pressure switch is "open" even when the tank pressure is full. I pulled the switch and bench tested it and its working. I put a jumper wire where the switch would plug into to trick the computer think its has full pressure but the software still says the switch is open. It's a very simple switch and is similar to the 5 ton series switches. You can manually inflate and deflate the tires using the software even if the tank pressure is low, or you have a bad switch.

The only thing I can think of is a break in the wiring harness?

 

[NDT]

Maybe an issue in the connector between the harness and the controller. Clean and reseat.

 

[Nomadic]

The computer may be looking for a specific resistance from the switch to determine its position.

 

[NDT]

The computer may be looking for a specific resistance from the switch to determine its position.

Yes like zero OR infinite. This is an analog input to the controller, it sends out probably 5 volts and looks for 5 volts to be coming back or not. Since this is no current, even the slightest resistance in the circuit due to corrosion etc will cause your symptom.

 

[jnissen]

Most analog sensors produce a voltage that is read by the ECU. Normally these are a high input impedance looking in. As a result the currents are very low. Online resistance is essentially a don’t care in that type of setup. As long as you get the voltage required and the harness is capable of connecting back to the ECU uninterrupted it should read. I suspect you have an open from corrosion or broken wire.

Setup a test with two dry cells (~3V). See where you can pick up the voltage and where it goes away. Your DMM will be your friend on this one.


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[MAdams]

This is a simple on or off switch. There is also a pressure transducer but that's for checking the tires pressure. The switch in question allows the ground to pass through when it reaches the appropriate pressure.

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[Elijah95]

Fighting the same issue, I’ll post if I come up with anything useful


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[MAdams]

Eli, have you jumped the pressure switch? I found the wiring diagram on dana's website. I'm going to trade it back to the controller

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[Elijah95]

Eli, have you jumped the pressure switch? I found the wiring diagram on dana's website. I'm going to trade it back to the controller

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Can you post a picture of the diagram? I might can test when continuing the AC install tomorrow


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[MAdams]

Eli, here is a quick video and it shows the diagram

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[Elijah95]

Maybe I’m reaching above my head, but if it’s saying it’s shorted, it may be realizing it’s too low of resistance.

That length of wiring, and the switch is going to create a certain amount of resistance. Either we can experiment with resistors to falsely create the “pressure good” amount of resistance, or if we can find just 1 guy with working ctis willing to unplug his controller and ohm it out with the truck aired up we could calculate and jump with a resistor.

You and I are fighting the exact same issue, I spent 4 hours on it the other day

 

[MAdams]

That could be. I'm thinking its much more simple and is just a go or no go. Like a low pressure cut out switch on a AC system.

The pressure sensor on the other hand would need precise ohms

 

[JonM934]

I have a working CTIS - sort of. My truck has a lot of air leaks and I have not plugged them yet so I have to have the truck running a long time to get enough pressure to get the CTIS functioning. But once it has the pressure, the CTIS works good. I can measure the resistance of that pressure switch once I get enough pressure to my CTIS. Actually, I guess it would be better to know both resistance readings, one where there is no pressure, and another reading when the proper pressure is achieved.

 

[JonM934]

OK, here is what happened. I went out to the truck, it was freezing, and the truck was off. I also know that there was no air pressure in the tank. I measured infinity ohms which makes sense. I left the sensor unplugged. So then I started the truck and it started building up air pressure. My CTIS was blinking the green LED on the Highway setting button. BUT mine always does that because it loses the air pressure.

I waited until the air pressure got to 120 PSI. Then I measured the resistance again. It was 1 ohm. I thought that cannot be correct, so I measured it a few more times. I even thought there might be a diode in there so I switched the leads on my multimeter to see if it made any difference. It did not make a difference. The reading was always 1 ohm. That seems really strange to me. 1 ohm is very difficult to detect in a circuit and it could be easily messed up by a bad connection or corrosion. But that is what I read. So then I plugged in the connector again and then I went to the cab to check the CTIS. It had the two steady green lights like it should.

 

[Elijah95]

OK, here is what happened. I went out to the truck, it was freezing, and the truck was off. I also know that there was no air pressure in the tank. I measured infinity ohms which makes sense. I left the sensor unplugged. So then I started the truck and it started building up air pressure. My CTIS was blinking the green LED on the Highway setting button. BUT mine always does that because it loses the air pressure.

I waited until the air pressure got to 120 PSI. Then I measured the resistance again. It was 1 ohm. I thought that cannot be correct, so I measured it a few more times. I even thought there might be a diode in there so I switched the leads on my multimeter to see if it made any difference. It did not make a difference. The reading was always 1 ohm. That seems really strange to me. 1 ohm is very difficult to detect in a circuit and it could be easily messed up by a bad connection or corrosion. But that is what I read. So then I plugged in the connector again and then I went to the cab to check the CTIS. It had the two steady green lights like it should.

Awesome info. What’s strange, is when I turn the ignition switch on, or crank the truck, there’s only 0-2 ton light on; the terrain mode never attempts to light, but if I mash one of the terrain buttons it will illuminate as long as the button is held. It will never attempt to blink


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[JonM934]

Here is photos of what I was talking about.


The 0-2 tons and the Highway lights are on steady.



This is the plug I checked and the sensor.

 

[Elijah95]

Here is photos of what I was talking about.
View attachment 787053

The 0-2 tons and the Highway lights are on steady.

View attachment 787055

This is the plug I checked and the sensor.

Good stuff, Like I mentioned can’t get the entire right side to light up unless I’m mashing one of the buttons, as soon as I let off nothing nada. Ima play with it more tomorrow. Total CTIS diagnostics time since purchase of truck: 13hrs


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[JonM934]

Wow, that is a lot of time spent on the CTIS. But I have heard that the CTIS can be hard to work on.

Let me know if there is anything else I can do and best of luck.

 

[Elijah95]

Wow, that is a lot of time spent on the CTIS. But I have heard that the CTIS can be hard to work on.

Let me know if there is anything else I can do and best of luck.

Thank you very much!


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[Elijah95]

Thank you very much!


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Managed to R&R my ctis manifold from the drivers side firewall, chasing a “short or break in control solenoid harness” code in the TIM diagnostics computer.

Couldn’t get my pressure switch to close, I jumpered my pressure switch, confirmed the TIM read switch as closed, and after replacing a couple solenoids in the ctis manifold suddenly the pressure switch began functioning! Low and behold I have a fully functioning CTIS.

I will do a full write up and post a video hopefully tomorrow


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