LMTV CTIS Question

[Third From Texas]

my bad..... confused myself... saw the FIVE and forgot in my haist there was a sold and flashing version of FIVE

LOL

I did the same in another group the other day. I didn't play the video and just saw five solid. Turned out, they were five flashing (in the video at least).

 

[Maddog Driver]

Thank you sir!

Alrighty...Our friend Plasa sent me his prototype, timely and excellent. Tires were at 55ish from last function of old controller. I used HWY to take them to 65ish. After the device was satisfied with the result, I selected Offroad and they deflated to 35-40ish and the controller seemed satisfied. Next, back to HWY and all four returned to 65ish but the controller kept working on one tire. Turns out the dump valve for the left front is stuck open and it will not hold any pressure. Can I locate and bang on the stuck valve, or is there a new part in my future ? The controller is not the problem and the other three re holding. Thanks again Plasa....

 

[Stellaevil]

Alrighty...Our friend Plasa sent me his prototype, timely and excellent. Tires were at 55ish from last function of old controller. I used HWY to take them to 65ish. After the device was satisfied with the result, I selected Offroad and they deflated to 35-40ish and the controller seemed satisfied. Next, back to HWY and all four returned to 65ish but the controller kept working on one tire. Turns out the dump valve for the left front is stuck open and it will not hold any pressure. Can I locate and bang on the stuck valve, or is there a new part in my future ? The controller is not the problem and the other three re holding. Thanks again Plasa....

Old wheel valves can be a problem and they will perform worse when it is colder out. Just take it apart and clean everything good. Remove any corrosion from the stainless seat and use a lightweight oil to soften the rubber diaphragm.

 

[Keith Knight]

I typically unplug my ECU when I'm not using the CTIS (in hopes to prolong its lifespan) but I hate the look of it and was going to just cut the power wire going to the ECU and install a switch so I can just turn it on or off when needed. Would there be any problem or reason I shouldn't do this. I do manually check the tire pressures regularly. I also check tire pressures after a deflating and reinflating them, always seem to have one not up to pressure and I just air it up individually with an air hose.
Also it looks like pin H is the power supply for the ECU, is this an accurate statement?

 

[coachgeo]

I typically unplug my ECU when I'm not using the CTIS (in hopes to prolong its lifespan) but I hate the look of it and was going to just cut the power wire going to the ECU and install a switch so I can just turn it on or off when needed. Would there be any problem or reason I shouldn't do this. I do manually check the tire pressures regularly. I also check tire pressures after a deflating and reinflating them, always seem to have one not up to pressure and I just air it up individually with an air hose.
Also it looks like pin H is the power supply for the ECU, is this an accurate statement?

are you speaking of the CTIS ECU? What would concern me if so..... is they say to unplug it before jump starting.. (this came up in a PS Mag. bulletin) Is that because it does not like sudden surges? if so.... then I would only use your kill switch for off/ons when the truck is OFF for same reasons.

 

[Ronmar]

I typically unplug my ECU when I'm not using the CTIS (in hopes to prolong its lifespan) but I hate the look of it and was going to just cut the power wire going to the ECU and install a switch so I can just turn it on or off when needed. Would there be any problem or reason I shouldn't do this. I do manually check the tire pressures regularly. I also check tire pressures after a deflating and reinflating them, always seem to have one not up to pressure and I just air it up individually with an air hose.
Also it looks like pin H is the power supply for the ECU, is this an accurate statement?

Well thats exactly what they did on the A1, a CTIS power switch. Depending on your vehicle, pin H may or may not be the power. I think they used power applied to various pins or combinations of pins from the sub harness to configure the CTIS controller for different applications. Different mode pressures, different fill time limits for 4 vs 6 wheels ect… I would not worry so much about the pin, I would look upstream to wire number 03 in the CTIS sub harness, or wire 1911 which carries the 24v ign power from CB40 and switch that…. see A1 drawing below, CTIS sw circled in red. The other contacts on the switch feed a “CTIS off“ light in the annunciator panel. the A0 uses the same wire numbers 03 in the CTIS harness and 1911 on the main wiring…

Switching the power on or off with a standalone sw or with the 24v ign relay using the main switch is the same thing.

I think the issue with jumpstarting is that because of the unpredictable battery and loading state, there is a real potential for spikes caused by the alternator when you unplug the jumpstart cable… alternator regulators are not very smart. It is the battery, like a filter capacitor on a power supply that stabelizes the output… This may have been the inspiration for adding the switch on the A1…

 

[Keith Knight]

Mine is a 2003 M1078A1 and I’ve never found a power switch for the CTIS ECU.

 

[Stellaevil]

Most Trucks that have a CTIS disable switch for an arctic kit use the pressure switch wire. This way is can be disabled before start up and easily engaged after running down the road and the seals are warmed up.
Take either with at the the switch, cut and splice two wires, then run them up to a new switch on the dash. Any switch will work as there is no current in this circuit. The ECU will flash 5 lights after 4 minutes at >20 MPH. This is good indication the system is non functional. A flip of the switch will clear the fault.

To answer the other question disconnecting the ECU connector on a powered truck will not damage the ECU as there are circuit protections. As a tech, I don't like to do it but have done it many times and never had a problem.

 

[Wingnut13]

So I have a 2003 1078A1 as well and had an interesting event regarding CTIS. For sure what I did wasn’t smart….. So I have a winch harness from an older gen truck. I plugged that in and it had a tach attached to the harness. When the I powered on the truck I got a green CTIS OFF light on my dash. Huh…. Never seen that before. Unplugged the tach from the harness and the light turned off. Probably not the best way to turn the system off, but if I can locate the correct wire I guess I just need a switch.

 

[Stellaevil]

So I have a 2003 1078A1 as well and had an interesting event regarding CTIS. For sure what I did wasn’t smart….. So I have a winch harness from an older gen truck. I plugged that in and it had a tach attached to the harness. When the I powered on the truck I got a green CTIS OFF light on my dash. Huh…. Never seen that before. Unplugged the tach from the harness and the light turned off. Probably not the best way to turn the system off, but if I can locate the correct wire I guess I just need a switch.

The only light for CTIS on the dash is the overspeed warning light. It should flash if the truck speed is exceeding the limit for the tire pressures and be on solid if the speed signal is no longer present after 50 key cycles. It will turn off as soon as the ECU sees a speed signal. Attaching a tach to the truck speed signal wire should not screw up the CTIS because it used dedicated signal wires from an analogue pole sensor.

 

[Ronmar]

The only light for CTIS on the dash is the overspeed warning light. It should flash if the truck speed is exceeding the limit for the tire pressures and be on solid if the speed signal is no longer present after 50 key cycles.

The drawing I am looking at says there is a CTIS off light(DS29). I only thought there was a ctis overspeed light, and on the A0 thats all there is. But apparently they were added in there at some point.

@Wingnut13 that other harness is probably your issue. No telling what they assigned the wires to in what year/variant sub harnesses. They do indicate that the power used to feed that CTIS off light via the switch comes from the vicinity of the winch on/off sw…

 

[Mavcaster]

The drawing I am looking at says there is a CTIS off light(DS29). I only thought there was a ctis overspeed light, and on the A0 thats all there is. But apparently they were added in there at some point.

Yes even my 01 A0.5 truck has a “CTIS OFF” light on the panel but there is no way from what I can tell with my config to make it illuminate outside of lamp test of course. I was also wondering about this light and seems like it’s only for the special arctic kit config mentioned.

 

[Ronmar]

Yes even my 01 A0.5 truck has a “CTIS OFF” light on the panel but there is no way from what I can tell with my config to make it illuminate outside of lamp test of course. I was also wondering about this light and seems like it’s only for the special arctic kit config mentioned.

I believe that is correct yes. You can access the wiring and wire in the switch. Like in tge drawing pic I posted, One half powers the CTIS controller while the other half powers that OFF light when you turn CTIS off.

Most of the wiring should be in the main truck harness as it connects to that idiot light panel and to CTIS already...

 

[Keith Knight]

So do you agree I could just cut the power wire to pin H on the CTIS ECU and add a switch then locate the “CTIS Off” lights wire and so it illuminates when it’s off?

 

[Ronmar]

You will need a double pole sw, but yes just like the drawing shows should work fine...

 

[Keith Knight]

Thanks ronmar I dug in this afternoon and found an empty plug behind the dash panel and it had the 1911 switch to 1911A and the 3020 switch to 1911B wires going to it. I jumpered them out and successfully got the CTIS OFF to illuminate and the CTIS turned on. Also take note there is another two pin plug that is the 1911 wires jumpered together so you’ll need to in plug it so the other wires can work if that makes sense. The empty plug that has all four wires needed.
This is the two prong plug that was just jumped that needs to be left unplugged.

 

[Keith Knight]

Well that project is finished. It was actually pretty straight forward after identifying the wires it was just a matter of splicing the four wires into a longer cable to the switch.

 

[Keith Knight]

Shout out to RONMAR for his posting of wire schematics and excellent advice and knowledge.

 

[Stellaevil]

You can disable the ECU by interrupting the PS Pressure Switch signal or put a 5 amp switch in line with the 24v power wire.
The ECU had protections against power surges and very robust. Welding on the chassis with the vehicle power on can cause issues but not jump starting.

 

[Awesomeness]

You can disable the ECU by interrupting the PS Pressure Switch signal or put a 5 amp switch in line with the 24v power wire.
The ECU had protections against power surges and very robust. Welding on the chassis with the vehicle power on can cause issues but not jump starting.

What document is this wiring diagram from?