Z 55, it's a four letter word

[Searay45db]

So just got me a '05 Denali XL. It has a Z55 suspension, and the pump would run on start up for two minutes easy a lot. I never got any messages. So ordered a new pump, threw it in, and great, runs for 6 seconds and stops. Next day after driving all day I get "Service Ride Control"

I have seen this show up before you replace it but not after you put a new compressor in. This is a Dornan, new, not rebuilt. When I pull codes, there are not any.

What's the scoop?

 

[Rocket Man]

First off, you'll never see any codes unless you have a Tech II scanner which is usually only found at a dealer. There could be several other problems besides the compressor. It could be the ride control sensors which are visible when you look towards the front of the rear wheels, they are mounted from the upper control arm to the frame. Look to see if one is bent or disconnected. Another thing is to inspect the rear air bags (shocks) to see if they're torn or if they're aftermarket. Some aftermarket shocks have electronic " spoofers" to fool the computer that the magnetic damping is working, and these can fail. Does the rear of your truck lift up a bit when the compressor runs? It should raise up a little until the ride height sensors are satisfied it's at the correct height. The front shocks also have electronic damping so if they're replaced with the wrong ones they will trigger that message. Also check the fuses in the under hood fuse block for any missing ones. STUD#1 and RTD (real time damping) are the 2 that I can remember that are for the ride control system. These systems can be hard to troubleshoot but in my opinion are worth fixing.

 

[Searay45db]

Well, no problem with fuses. Prior to putting in the new A/C, pump was running long periods. Put the new one in, ran for about 7 seconds upon start up. There was service error. It took a day for the service system to appear. I have inspected the rears, even put soapy water on them to see leaks as I did not hear any.

RTD, 30 AMP is fine, and so is STUD #1. It's odd it went from running all of the time. However, I marked the shocks a week before when it was running constantly. Checked the shocks afterwards, and there was no change in the position of the shocks.

Will the dealer just scan it? Do you just need a Tech II scanner or do you need the GM one?

Thanks

 

[Rocket Man]

Tech II is the scanner the GM dealer uses. Snap-On makes one that reads the suspension codes also, you'll have to check with shops to see if they can pull Suspension Control Module codes. Sounds like it's not raising the rear up so the message appears. Not sure why it didn't show up before. I had a wiring harness up front come unplugged once that caused the message, as well as other things.

 

[Searay45db]

I thought the pump should run for about 15 seconds when the truck starts. The old pump ran for two minutes. This pump 6 seconds.

 

[Rocket Man]

I thought the pump should run for about 15 seconds when the truck starts. The old pump ran for two minutes. This pump 6 seconds.

It depends on how much air leaked out. If nothing leaked it doesn't turn on every time. Mine runs for 10- 15 seconds or sometimes not at all. If I put my trailer on it runs for a minute or so.

 

[Searay45db]

So it its not needing to run, new pump, its frick'n strange that now after the new pump is on that this is coming up. Wonder if I put something together wrong...

 

[Searay45db]

So here is the other question, is the suspension system working during this time?

 

[Searay45db]

It depends on how much air leaked out. If nothing leaked it doesn't turn on every time. Mine runs for 10- 15 seconds or sometimes not at all. If I put my trailer on it runs for a minute or so.

Ok, so I took the wheel off, and removed the connections, air connections from the pump and ran it. Only ran 6 seconds. Then I put the old pump on, same thing. I then put the new one back on, making sure the electrical connections were correctly seated. Lowered the truck, pump ran for about 18 seconds, it actually gave like a burp before pumping and no error codes. Started it again and again and again, no more codes. Pump burps, runs maybe 4 seconds.

Thoughts?

 

[Rocket Man]

It may just have needed to reset itself. There's an actual computer module behind the rear passenger side panel called the Suspension Control Module and it goes through a system check and calibration every time you start the engine. When you changed the compressor it may have sensed something changed but never was able to calibre the system. Sounds like you're good to go.