What did you do to your NNBS GMT900 Tahoe/Yukon Today?

[swathdiver]

so it makes it throw every gizmo crazy? makes the rmp gauge drop to 0?, seems rather strange to me

Yep, makes you think the whole thing just went crazy and broke and my wallet felt like it was emptying FAST! It is best to either use it while running or while it is off. Certain places will allow you to have it on with the engine off and then start the engine if I remember right. Gotta plug it in first with the engine off. I have also left it running, shut the car off and then it freaked out when I started the truck back up. There's a certain way to use it, I'm still learnin' the hard way and with my wonderful memory, may never get it!

 

[Doubeleive]

Yep, makes you think the whole thing just went crazy and broke and my wallet felt like it was emptying FAST! It is best to either use it while running or while it is off. Certain places will allow you to have it on with the engine off and then start the engine if I remember right. Gotta plug it in first with the engine off. I have also left it running, shut the car off and then it freaked out when I started the truck back up. There's a certain way to use it, I'm still learnin' the hard way and with my wonderful memory, may never get it!

ok thanks for the feedback I take it then that service manager hasn't used one these much then as we were both like wth? good to know

 

[swathdiver]

ok thanks for the feedback I take it then that service manager hasn't used one these much then as we were both like wth? good to know

If there is a next time, have him plug it in with the truck off, then turn on the truck, engine running, then power up and use the Tech2.

 

[PG01]

ok thanks for the feedback I take it then that service manager hasn't used one these much then as we were both like wth? good to know

Same thing happened to my honda a few months back, plugged in a simple code reader while driving and dashboard lit up like a Christmas tree....it was in P,R,N,D,1&2 at same time while i was doing 65 down the road... every light that could be on was...pulled over shut if off started it and it was fine... thats my little tidbit for the day....

 

[Doubeleive]

I could be wrong but I don't think the pump gets power until the key is actually in the run position just like the radio and other things don't turn on until the key is in.

If the compressor is functioning properly then the compressor should turn on for a few seconds after starting the truck with the key.

After you shut the truck off if you stand near the gas tank filler you should hear the compressor dump a little and stop and dump a little and stop... it will do this multiple times before it stops. It should dump the air everytime the truck is turned off.

so does your pump run every time you start the truck? even if it was only parked for a couple minutes? just wondering because mine does not run every time hasn't since I owned it.

 

[kbuskill]

so does your pump run every time you start the truck? even if it was only parked for a couple minutes? just wondering because mine does not run every time hasn't since I owned it.

Yes... but only for a few seconds... it is a self check for the compressor. Also, as I mentioned, it dumps everytime I park the truck and turn it off.

My guess is that your exhaust valve is malfunctioning which is not allowing the shocks to dump when you park and shut off the truck.

If this is true then I would think that since the auto level sensors are already reading that the truck is at proper ride height it will not allow the compressor to turn on for the self check because it would raise the truck above "normal ride height" and since it can't test, it sets the service suspension light.

This is all just my best guess.

I also know that the compressor opens the exhaust valve at compressor start up to reduce the amperage draw on the compressor motor.

It's kinda like a decompression valve on a motorcycle engine or on a chainsaw.

Higher compression engines require a decompression valve to allow the rotating assembly to get spinning without a load to make them easier to start. Once the crank and pistons have momentum the decompression valve closes and compression is built.

Same for these compressors... no load = less amperage drawn = easier to start moving.

The Tech2 should allow you to command the dump/exhaust valve on to see if it works.

To me it sounds like you need a new compressor but having access to the Tech2 could save you some money if that is not it.

 

[kbuskill]

@Doubeleive

Just thought I would post this from another site...

The ESC module has the ability to store DTCs as current or history codes. The system uses an ignition cycling diagnostic approach in order to reduce the occurrence of false or intermittent DTCs that do not affect the functionality of the system. This allows for the fail-soft actions to be taken whenever a malfunction condition is current, but requires the malfunction to be current for a certain number of ignition cycles before the corresponding malfunction code and message will be stored or displayed. The Automatic Level Control (ALC) system maintains a desired rear suspension position under all types of towing, hauling and loading conditions. The system uses the Electronic Suspension Control Module (ESCM) and the serial data circuit to perform the system functions. When the vehicle is unloaded, the rear suspension is at a desired position, which is monitored by the ESCM using the position sensor inputs. As weight is added to the rear of the vehicle, the position sensor’s signal voltage inputs change.

When the ESCM detects a steady substantial change in the position sensor signal voltages for at least 10 seconds, it responds by commanding ON the ELC relay, which activates the compressor causing the air pressure in the shock absorber chambers to inflate. This inflation raises the rear of the vehicle to regain the desired suspension position. When weight is removed from the vehicle, the ESCM responds by commanding ON the exhaust valve causing the air pressure in the shock absorber chambers to deflate.

Each time the compressor is activated, the ESCM commands ON the exhaust valve for 1.5 seconds to release air from the compression chamber in the compressor’s cylinder head, ensuring low motor current draw upon compressor activation. The ESCM also limits the amount of compressor run time to 255 seconds to protect the compressor components from thermal damage.

The system also performs a self-test on each ignition ON cycle in which the ESCM commands the ELC relay ON, activating the compressor for 4 seconds, then monitors the position sensor’s signal voltage inputs to verify the compressor is functioning and the system is holding air pressure.

If you want to read more, here is the site...

http://www.tomorrowstechnician.com/?s=Ride control

I just pulled the parts that apply to your situation.

 

[Doubeleive]

@Doubeleive

Just thought I would post this from another site...

The ESC module has the ability to store DTCs as current or history codes. The system uses an ignition cycling diagnostic approach in order to reduce the occurrence of false or intermittent DTCs that do not affect the functionality of the system. This allows for the fail-soft actions to be taken whenever a malfunction condition is current, but requires the malfunction to be current for a certain number of ignition cycles before the corresponding malfunction code and message will be stored or displayed. The Automatic Level Control (ALC) system maintains a desired rear suspension position under all types of towing, hauling and loading conditions. The system uses the Electronic Suspension Control Module (ESCM) and the serial data circuit to perform the system functions. When the vehicle is unloaded, the rear suspension is at a desired position, which is monitored by the ESCM using the position sensor inputs. As weight is added to the rear of the vehicle, the position sensor’s signal voltage inputs change.

When the ESCM detects a steady substantial change in the position sensor signal voltages for at least 10 seconds, it responds by commanding ON the ELC relay, which activates the compressor causing the air pressure in the shock absorber chambers to inflate. This inflation raises the rear of the vehicle to regain the desired suspension position. When weight is removed from the vehicle, the ESCM responds by commanding ON the exhaust valve causing the air pressure in the shock absorber chambers to deflate.

Each time the compressor is activated, the ESCM commands ON the exhaust valve for 1.5 seconds to release air from the compression chamber in the compressor’s cylinder head, ensuring low motor current draw upon compressor activation. The ESCM also limits the amount of compressor run time to 255 seconds to protect the compressor components from thermal damage.

The system also performs a self-test on each ignition ON cycle in which the ESCM commands the ELC relay ON, activating the compressor for 4 seconds, then monitors the position sensor’s signal voltage inputs to verify the compressor is functioning and the system is holding air pressure.

If you want to read more, here is the site...

http://www.tomorrowstechnician.com/?s=Ride control

I just pulled the parts that apply to your situation.

ya im just going to get the arnott from rock auto, lifetime warranty so one time expense and done, the pump is not coming on each time, we just went down the street to have pizza, jumped back in the truck to come back home after eating the pump didn't come on and the error popped back up again on the dic, I was thinking just a couple days ago too that I hadn't noticed the pump coming on as much or at all. roll the dice and see what happens.

 

[Doubeleive]

gotta love rockauto, one of there main wharehouses is only about 50 miles from me overnight shipping was only a extra $10 and the %5 off code saved me $11.00 lol

 

[aflumb]

Well I was back to working on the truck some more today.


Well I actually started yesterday, so in total about 6 hrs into this little project

Replaced the rear view cam, removed the amp that never got used, and cleaned up a lot of my wiring to a simpler set up.

This is what all was removed


Now after getting everything back together; put in reverse and no cam. Oh well try again tomorrow. And I tested it every step of the way.


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