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2012 Avalanche LS "Service Suspension System" but no air-ride?!?!

coolcolek44

New Member
Joined
Jun 4, 2020
Messages
4
Location
Canada
Hey guys, ever since I bought my 2012 LS I have had an issue where it says "service suspension system" on the DIC. I've always though this was strange because I was under the impression that only owners with LTZ's and air ride suspension could actually get this error message and upon looking at the owners manual that seems to be the case. My 2012's suspension RPO codes only include the ZW7 'smooth ride package' which to my understanding is a pretty traditional simple setup. This has never been an issue for me, just an annoyance having to clear it every time I drive the truck but now im in the process of selling the truck and would like to figure out what the issue is so the next owner wont have to deal with it. I have done quite a bit of research on this but everyone that is getting this message seems to have trucks with an air-ride setup from the factory. I have also checked all the fuses pertaining to the suspension system but to no avail, any suggestions would be greatly appreciated! :help:
 
Try using the search feature as you will find a plethora of information on this issue

https://www.chevyavalanchefanclub.com/cafcna/index.php?action=search2

 
I am not familiar with the 2012 LS Avalanche, so I am just venturing a guess or two here.

When you checked for fuses, was there one in the under hood fuse box for RTD or Real Time Dampening?

On my 2004 Cadillac Escalade EXT, it has the RPO code Z55 Chassis Package Bi-State, Real Time Damping in addition to the RPO code G69 Level Control Auto, Air, HD for the air shock system.

All four of my OEM shocks were part of the RTD system, but only the two rear shocks were part of the leveling system.

The RPO code Z55 refers to the truck having shocks at all four corners that are connected electrically to the truck's computer.

You should see some sort of wiring connector plugged into the upper portion of the shock.

The computer is able to adjust valving inside the shock according to need to maintain the desired ride firmness at all times.

It may be possible that your truck was factory equipped with those type of shocks and a previous owner replaced them with standard shocks because of the cost of the OEM replacements.

That is not all that uncommon since the RTD shocks tend to be much more expensive.

What some owners do not know or understand, when replacing the OEM shocks, they must also install special resistors at the point where the wiring pigtail normally plugs into each OEM shock.

If the computer does not see the normal OEM shock or the resistor, it senses that something is wrong with the system and it will command the error message you are seeing to be displayed.

You should be able to locate the wiring pigtail near each of the four shocks.

Hopefully, the previous owner did not just cut the pigtail off.

If the pigtail is there, you have a couple of options.

Purchase and install the correct OEM shocks and plug the pigtail into those shocks and regain the RTD function on your truck.

Or, locate and install the correct resistors at each wiring pigtail and secure those under the truck so that the computer sees what it is looking for and quits displaying the error message.

Or, if your truck is so equipped, like older models of these trucks are, if there is an RTD fuse in the under hood fuse box, with the truck turned off, remove that fuse then disconnect the battery and after a minute or so hook the battery back up and start the truck, leaving the RTD fuse out.

On older models of these trucks, that procedure will cause the computer to stop looking for the RTD system and your error light will not be displayed any more.

Anyway, these are just a few thoughts I had that may or may not apply in your situation.

Let us know what you come up with.
 
EXT4ME said:
I am not familiar with the 2012 LS Avalanche, so I am just venturing a guess or two here.

When you checked for fuses, was there one in the under hood fuse box for RTD or Real Time Dampening?

On my 2004 Cadillac Escalade EXT, it has the RPO code Z55 Chassis Package Bi-State, Real Time Damping in addition to the RPO code G69 Level Control Auto, Air, HD for the air shock system.

All four of my OEM shocks were part of the RTD system, but only the two rear shocks were part of the leveling system.

The RPO code Z55 refers to the truck having shocks at all four corners that are connected electrically to the truck's computer.

You should see some sort of wiring connector plugged into the upper portion of the shock.

The computer is able to adjust valving inside the shock according to need to maintain the desired ride firmness at all times.

It may be possible that your truck was factory equipped with those type of shocks and a previous owner replaced them with standard shocks because of the cost of the OEM replacements.

That is not all that uncommon since the RTD shocks tend to be much more expensive.

What some owners do not know or understand, when replacing the OEM shocks, they must also install special resistors at the point where the wiring pigtail normally plugs into each OEM shock.

If the computer does not see the normal OEM shock or the resistor, it senses that something is wrong with the system and it will command the error message you are seeing to be displayed.

You should be able to locate the wiring pigtail near each of the four shocks.

Hopefully, the previous owner did not just cut the pigtail off.

If the pigtail is there, you have a couple of options.

Purchase and install the correct OEM shocks and plug the pigtail into those shocks and regain the RTD function on your truck.

Or, locate and install the correct resistors at each wiring pigtail and secure those under the truck so that the computer sees what it is looking for and quits displaying the error message.

Or, if your truck is so equipped, like older models of these trucks are, if there is an RTD fuse in the under hood fuse box, with the truck turned off, remove that fuse then disconnect the battery and after a minute or so hook the battery back up and start the truck, leaving the RTD fuse out.

On older models of these trucks, that procedure will cause the computer to stop looking for the RTD system and your error light will not be displayed any more.

Anyway, these are just a few thoughts I had that may or may not apply in your situation.

Let us know what you come up with.

Thanks for the reply and I appreciate the suggestions. Unfortunately my only fuse pertaining to the suspension system is fuse #3 which is labelled "ESC/ALC EXH (30A)" and it is intact. I have a list of the factory RPO codes for my exact VIN from a local dealer and my suspension codes are 6SH, 7SH, and ZW7 meaning it had a traditional setup from the factory. I took a look at all 4 shocks on the truck just to make sure and they are indeed traditional gas shocks with no wiring or pigtails present in the area I also checked the location the compressor would normally be on the higher trim trucks and I didnt have one and no wiring was in the general vicinity either. The thing that has me stumped is that to the best of my knowledge these base model LS trucks were not available with the Z55 air ride package so I don't believe it was possible that the previous owner has air ride on the truck at any point in time. :E:
 
Loggie said:
Try using the search feature as you will find a plethora of information on this issue

https://www.chevyavalanchefanclub.com/cafcna/index.php?action=search2

Thanks for the reply. As mentioned I am aware there is plenty of information on the dreaded service suspension message but it all seems to come from owners with the equipped Z55 air-ride package from the factory. However I believe my case is unique to all of the other posts because my truck is a base model and was not equipped with air-ride from the factory but I am still getting this error ???. I have yet to find someone with a similar issue on the forums.
 
coolcolek44 said:
Thanks for the reply. As mentioned I am aware there is plenty of information on the dreaded service suspension message but it all seems to come from owners with the equipped Z55 air-ride package from the factory. However I believe my case is unique to all of the other posts because my truck is a base model and was not equipped with air-ride from the factory but I am still getting this error ???. I have yet to find someone with a similar issue on the forums.

I understand better now...sorry about my misread.  What did the dealership tech have to say?  Maybe its a fault in the cluster. Like if all the clusters are used for every model then maybe the DIC is just throwing a fault for some unknown reason :rolleyes:
 
Loggie said:
I understand better now...sorry about my misread.  What did the dealership tech have to say?  Maybe its a fault in the cluster. Like if all the clusters are used for every model then maybe the DIC is just throwing a fault for some unknown reason :rolleyes:

No problem, have yet to take it to the dealership or hook it up to a high-tech scan tool but im beginning to think you are right regarding the cluster. That seems like the only thing that would makes sense at this point. Ever since I bought the truck I have been suspicious of the mileage and thought it was possible a different cluster was swapped in. Could be that a cluster from a previous LTZ truck equipped with air-ride Z55 was swapped in and it is confusing the computer and tripping the code or something!?!? Who knows  :E: Ill do some more digging next week and keep you guys posted.
 
I think a trip to the dealer for a scan may be in order.

On both of my trucks, I replaced and upgraded the clusters.

The vendor installed my VIN and mileage into the clusters as part of the deal.

I am not certain exactly how important those steps were, but it made both of my new clusters plug and play.

I am wondering if your truck's computer has some feature turned on that is not available.

Maybe something having to do with the suspension.

I know that owners of trucks with the AFM system can have that turned off in the computer when doing an AFM delete on their engines.

I would think the dealer's scan tool would be able to confirm that something may be turned on that shouldn't be and then turn that feature off.

Perhaps a reflash of the computer is in order to sort things out.

Just some more thoughts.
 
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