RESOLVED: Dash gauge issues when CTIS plugged in?

Rbernard1984

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Hello all! Have been lurking on the forums for a bit and recently picked up an 05 1078. So far has been a great truck and limited issues. However since I bought it I have had one issue I cannot seem to sort out. Whenever the CTIS ECU is plugged in I loose oil pressure on the dash and sometimes get a charge fault. I thought maybe it was a ground or batter issue, but that does not seem to be the case. Anyone with an idea on what might be causing this?
 

Ronmar

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It could be that it is doing something to the J1587 data buss. I am assuming that your truck uses the integrated gauge controller, because that is about the only way I could see your CTIS effecting oil pressure, who's information is also passed on the J1587 buss in vehicles using the integrated gauge controller(MMDC)

1st question, is it the correct controller for the truck? If not, this type of programming conflict could result...
 

Rbernard1984

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It could be that it is doing something to the J1587 data buss. I am assuming that your truck uses the integrated gauge controller, because that is about the only way I could see your CTIS effecting oil pressure, who's information is also passed on the J1587 buss in vehicles using the integrated gauge controller(MMDC)

1st question, is it the correct controller for the truck? If not, this type of programming conflict could result...
I just removed the box and this is the label on it. Does that look correct for a 2005?
 

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Rbernard1984

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Here's what's on my 2008 (w/C7)

It's actually green.
Interesting, wonder if someone changed the ecu and it’s not playing happy. When I removed it I noticed the ground wire was on the outside of the box, wonder if it was not grounding properly either. Will have to start it up tomorrow and see if that changed anything.
 
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Ronmar

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Interesting, wonder if someone changed the ecu and it’s not playing happy. When I removed it I noticed the groin wire was on the outside of the box, wonder if it was not grounding properly either. Will have to start it up tomorrow and see if that changed.
I don’t think the ground wire makes any difference in operation, I believe it was done to meet some EMI/shielding specification, since they didn’t tie the CTIS case to ground in the cannon plug. Just like they put EMI filters on the wiper, washer and heater blower motor circuits...

In the A1 and A1R drawings I have seen, the CTIS doesn’t appear to use the data busses in operation. It still gets it’s speed input separately(from speedometer) and sends out it’s overspeed signal via hardwire to the MMDC And gets a blackout(dimmer) signal from the lighting circuits. That and it’s own display lights are it’s only interfaces with other truck systems and the operator, same as in an A0... I think they tied it in to the busses simply to make it more easily accessible for a technician to connect to and communicate with all the controllers on the truck From a single port.

Is that CTIS module doing what its supposed to do/fully functional?

If so, you can research wether yours is the right unit or not and if not replace it.
Or
You can open up the cannon plug on the harness and disconnect the 4 wires used by the two comms busses, insulate/heat shrink the ends of the wires and move on to something else to occupy your time(and wallet) :)
 

Rbernard1984

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I don’t think the ground wire makes any difference in operation, I believe it was done to meet some EMI/shielding specification, since they didn’t tie the CTIS case to ground in the cannon plug. Just like they put EMI filters on the wiper, washer and heater blower motor circuits...

In the A1 and A1R drawings I have seen, the CTIS doesn’t appear to use the data busses in operation. It still gets it’s speed input separately(from speedometer) and sends out it’s overspeed signal via hardwire to the MMDC And gets a blackout(dimmer) signal from the lighting circuits. That and it’s own display lights are it’s only interfaces with other truck systems and the operator, same as in an A0... I think they tied it in to the busses simply to make it more easily accessible for a technician to connect to and communicate with all the controllers on the truck From a single port.

Is that CTIS module doing what its supposed to do/fully functional?

If so, you can research wether yours is the right unit or not and if not replace it.
Or
You can open up the cannon plug on the harness and disconnect the 4 wires used by the two comms busses, insulate/heat shrink the ends of the wires and move on to something else to occupy your time(and wallet) :)
Awesome, very helpful.

The unit has no flashing lights and inflates/deflates to the correct pressure for each program. However I have not connected to it to verify any faults.

Would you be able to point me in the direction of a wiring diagram to identify those 4 wires?
 

Ronmar

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Port angeles wa
Awesome, very helpful.

The unit has no flashing lights and inflates/deflates to the correct pressure for each program. However I have not connected to it to verify any faults.

Would you be able to point me in the direction of a wiring diagram to identify those 4 wires?
In the cannon plug that connects to the CTIS controller, Lower case a and capital N are the pins used by the J1587 buss.
Capital G and X are used by the j1939 buss.
 

Rbernard1984

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Thanks everyone for the help on this, just wanted to provide an update. Hopefully help anyone else with a similar issue.

The issue is resolved and it was two things. First, the ground wire was placed outside the CTIS box against the plastic and was not properly grounding. Once the ground wire was inbound the gauges all stayed on, so the ground in the harness is important to the system in some fashion. So, if you are having gauge issues that go away when the CTIS is unplugged check your ground.

Second, once the ground was connected the CTIS was coming on and all five lights were illuminated, whereas it appeared to function normal before even though it was clearly having issues. After some trouble shooting I found that the small “valve” that is under the passenger foot well with 1/4 line in and out, was leaking. Someone had repaired it with push in connections and not the brass compression connections. Once that was properly repaired the CTIS reset and started functioning normally.

In the end it was two parts, the CTIS was throwing an error, but because of the ground wire issue it wasn’t showing a solid light pattern, but instead causing the dash gauges to have issues. With the leak fixed and proper grounding the system works perfect. $12 in parts and on to the next project!
 

Mullaney

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Awesome.

Yes, they are not just a truck they are an adventure !

;)
Absolutely! Seems that most everything always takes a little more time (or money) to fix every problem.
It sure is nice though when a $12 fix is the solution.

More often mine seem to be in the hundreds - but I still enjoy the toys :cool:

.
 

Ronmar

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685
93
Location
Port angeles wa
Thanks everyone for the help on this, just wanted to provide an update. Hopefully help anyone else with a similar issue.

The issue is resolved and it was two things. First, the ground wire was placed outside the CTIS box against the plastic and was not properly grounding. Once the ground wire was inbound the gauges all stayed on, so the ground in the harness is important to the system in some fashion. So, if you are having gauge issues that go away when the CTIS is unplugged check your ground.

Second, once the ground was connected the CTIS was coming on and all five lights were illuminated, whereas it appeared to function normal before even though it was clearly having issues. After some trouble shooting I found that the small “valve” that is under the passenger foot well with 1/4 line in and out, was leaking. Someone had repaired it with push in connections and not the brass compression connections. Once that was properly repaired the CTIS reset and started functioning normally.

In the end it was two parts, the CTIS was throwing an error, but because of the ground wire issue it wasn’t showing a solid light pattern, but instead causing the dash gauges to have issues. With the leak fixed and proper grounding the system works perfect. $12 in parts and on to the next project!
Interesting...

The small valve with the 1/4” lines(all the way to the right?) is for the fan clutch control. It should energize with the main switch turned on and de-energize(and vent air) when y0u turn the main switch off...
 
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