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Dave Nova
Dave Nova, Cadillac Technician
Category: Cadillac
Satisfied Customers: 1522
Experience:  ASE Master Certification. GM World Class Certification
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I have an 03 escalade with a rear suspension issue. The

Customer Question

I have an 03 escalade with a rear suspension issue. The following items have been replaced: stud1 fuse, relay in engine compartment, fuse in driverside fuse box, front and rear shocks, compressor. The issue is that the compressor continues run nonstop and the only way I can stop is to pull stud1 fuse. The exhaust valve will cut off eventually although the compressor continues to run. I have also tested levelers to see if I change the height it would stop the compressor from running without success. I am running out of ideas here.
Submitted: 5 months ago.
Category: Cadillac
Expert:  Wayne Crawford replied 5 months ago.

Hello. My name is ***** ***** I will be helping you today.

Wheres the air coming out?

Customer: replied 5 months ago.
Air coming out ? I do not understand your response. If you are referring to the air in the shocks. I have used soapy water to test the lines and connections. Once the shocks are fully expanded they hold pressure for a day if the vehicle sits there. If I drive the vehicle with the shocks full they stay inflated for approximately a tank of gas or 350 miles.
Expert:  Wayne Crawford replied 5 months ago.

If the compressor constantly runs and air is not coming out anywhere the pressure would build up until something exploded. If the compressor is running continuously SOMETHING is leaking. You need to recheck for leaks.

Customer: replied 5 months ago.
I just tested it again this morning and the vehicle continues to lift to the point where I am concerned that the shock bags will blow out. How high should the vehicle raise and how long should it run for ?
Customer: replied 5 months ago.
Also the pressure valve does pop off and the compressor continues to run.
Expert:  Wayne Crawford replied 5 months ago.

It shouldnt run for more than a minute and the relief valve should not pop and the compressor still run.

Do you have a meter to do some testing?

Customer: replied 5 months ago.
I have a voltmeter will that be sufficient ? I am expecting delivery of a scan tool later this week.
Expert:  Wayne Crawford replied 5 months ago.

Its a good start. We can see how far we can get with it and if we end up needing a scan tool we will have to wait.

Expert:  Wayne Crawford replied 5 months ago.

Just a minute while I pull your vehicle up and look over a diagram on your system.

Expert:  Wayne Crawford replied 5 months ago.

Do you have an ohm meter?

Customer: replied 5 months ago.
I do.
Expert:  Wayne Crawford replied 5 months ago.

Unplug the compressor and check the resistance between where the orange wire was and where the dark blue wire was on the compressor side of the connector.

Customer: replied 5 months ago.
I will take a picture of the compressor side of the plug as I do not see an orange wire only pink/red.
Expert:  Wayne Crawford replied 5 months ago.

Ill wait for it.

Customer: replied 5 months ago.
I was incorrect turns out there was a small orange wire. What setting for the ohms should I have the meter set at and I will go test it again. Can you confirm if the wires in the plug are in the correct order as the previous mechanic may have moved them around and I wouldn't have known. I could not get a straight answer from him which is why I ask.
Customer: replied 5 months ago.
No ohms reading between orange and blue for all settings on my voltmeter. Does the vehicle need to be on ?
Expert:  Wayne Crawford replied 5 months ago.

Why would you suspect he moved them around?

They do not appear to be correct. Ill provide a pinout here for you.

Expert:  Wayne Crawford replied 5 months ago.

Are you checking the compressor sire or the truck wiring harness side?

Customer: replied 5 months ago.
I was looking at the compressor side. I have been looking for this pinout diagram do you have the same diagram for the compressor side if so please send as it is different from the car side? The reason I suspect the previous mechanics was 1) they installed the compressor 2) they are not electrically inclined to say it nicely.
Expert:  Wayne Crawford replied 5 months ago.

What do you mean its different on the compressor side. There are two identical but mirrored sides of a plug. They wouldnt plug in to each other if they were different.

Customer: replied 5 months ago.
To clarify the plug matches on both sides however the wiring is different on one side from the other. There are different color wires connecting to eachother which is what led me to believe there was a discrepancy. I just went and looked again and the colors appear to be in different pin locations on the compressor to that of the truck side. That is why I was asking about a pinout for the compressor side female side of the plug. To confirm I compared the truck side of the plug and it matches the diagram you sent.
Expert:  Wayne Crawford replied 5 months ago.

OK. A diagram of the compressors wiring between the actual motor and the connector is not available. It is serviced as an assembly. I dont have one here to physically check or I would. If this mechanic is not very skilled with electronics I am going to assume they did not reconfigure the pins.. it would take a terminal removal kit which is an expensive tool not many people who dont know much about electronics would spend the money on.

Customer: replied 5 months ago.
The issue is that he had to cut and splice the wires from the old plug onto the new compressor. I can find the instructions from Arnott however without the diagram I am concerned this is an issue that may be the culprit. Also to reconfirm I received zero response on my ohm meter when I tested the orange and blue wire.
Expert:  Wayne Crawford replied 5 months ago.

Im limited to factory information here. I dont have an "internal" wiring diagram on an aftermarket compressor motor to tell you what is what. You would have to email the manufacturer of the compressor to ask them the function of each color wire on their compressor OR dismantle it and see where each wire goes to see if the wiring is right. Their instructions SHOULD tell you which wire on their compressor connects to which wire on the factory connector but I am not looking at their instructions. I do believe the wires are probably not properly installed and that could be your issue but without a wiring diagram from them its only speculation. You cant test the two wires properly without knowing the wires are in the right spot either.

Customer: replied 5 months ago.
attached are the Arnott instructions. Let me know your thoughts
Expert:  Wayne Crawford replied 5 months ago.

Seems straight forward enough. Red on your new compressor to red on the original connector. Black on your new compressor to black on the original connector. Blue and white on your new compressor to blue and white.

Expert:  Wayne Crawford replied 5 months ago.

I cant see the other ends of your wires but it would take a really lacking mechanic to mess that up.

Expert:  Wayne Crawford replied 5 months ago.

Actually thats blue and grey on the factory side but it looks right from what I can see. I actually do see a butt connector there and it looks like the other side is grey.

Customer: replied 5 months ago.
I can take as many pictures as you need but without knowing what the original plug wires were I am confused as to what is correct. I was trying to look at used compressors on ebay as a reference and didn't see any that gave clear images of the compressor side of the plug. I do not know what I am ohm testing if the wires are not correct.
Expert:  Wayne Crawford replied 5 months ago.

Ohm test between the blue and grey wires

Customer: replied 5 months ago.
reading was 18.5 ohms
Expert:  Wayne Crawford replied 5 months ago.

Check the voltage on the orange wire on the vehicle side while cycling the key on and off.

Expert:  Wayne Crawford replied 5 months ago.

Actually I confused you with another customer. Yours is constantly running. That will be fine.

At this point you need suspension codes.

Customer: replied 5 months ago.
Ok. I am waiting for the scan tool to arrive later today and will respond as soon as I have them assuming there are any.
Expert:  Wayne Crawford replied 5 months ago.

There will be suspension codes. I will be around just reply when you get them.

Customer: replied 5 months ago.
Ok I have numerous codes none appear to be related to the suspension. Most are old as I had a fuel pump go bad and had to replace. I just purchased an NT510 foxwell so if there are specific tests I should perform please advise.
Here are the codes. p0151 p0157 p0171 p0174 p0131 p0137
Expert:  Wayne Crawford replied 5 months ago.

There are suspension codes but none of those are them. Your scan tool just doesnt communicate with the suspension module if you arent getting the codes.

Expert:  Wayne Crawford replied 5 months ago.

If possible see if any of your friends have a decent scan tool.... snap on, cornwell, tech 2, launch.. all of those and many more will read suspension codes.

Customer: replied 5 months ago.
Ok. I will attempt a more in depth scan I just performed a obdii initial scan. I am the mechanic amongst my friends.. sadly.
I believe I can request updates from Foxwell for specific aspects if it does not have currently loaded. Will research further.
Expert:  Wayne Crawford replied 5 months ago.

If you have the option to put in vehicle information put it in. Many times if you dont put in the year make and model it will only give you generic codes. You have to put in the vehicle information to connect to the ABS, Transmission, Etc.

I am not familiar with your scan tool so I dont know if it supports GM suspension modules.

Customer: replied 5 months ago.
According to foxwell for the nt510 it does although their customer service is slow. I purchased it to work on my Bmw as it has specific software for that model however it also has basic obdII and can be upgraded to support GM. I purchased the upgrade and it has been challenging to say the least to finalize. Outside of that my concern is that the issue is still related to the question of whether the original wiring was done properly and if so what is causing the compressor to run constantly. I should mention I removed the levelers on each side and attempted to test if the pump would cut off if I moved the arm to a fully extended position and no change. I also changed the suspension ecm out to a known good one and nothing different. If I had know it would be this difficult to get the suspension to work I would have swapped to regular shocks a long time ago.
Expert:  Wayne Crawford replied 5 months ago.

Does it show live data in the suspension module?

And yeah if it were me that would have been my first move. Im not a fan of the OEM air suspension. They are all problematic.

Customer: replied 5 months ago.
It does show suspension codes for my Bmw however I do not have the correct software module for GM. I have purchased it but cant download and am waiting for customer service. Will advise Monday once I get the software sorted out. in the meantime did you have any luck finding a old plug from a compressor by chance so I can put my mind at ease regarding the wiring ?
Expert:  Wayne Crawford replied 5 months ago.

Unfortunately I have not. With the heat wave we have been having I have been parked at this computer in the air conditioning.. not even working on anything.

Customer: replied 5 months ago.
After 2 hours of scanning and the latest software Foxwell has to offer I have come to the conclusion that there are no current or historic codes for the suspension. I also have come to the conclusion that there is a challenge for testing each of the components as the tests take some time to run and I have the plug at the compressor disconnected as it just runs nonstop and I do not want to blow out the rear shocks so I only have a limited time to run each individual test to determine where the issue may lie. Not sure how to overcome this issue since the culprit is causing me not to be able to test the system. Any fresh ideas?
Customer: replied 5 months ago.
Ok I finally found a plug to compare. Please take a look and confirm your thoughts given the attachments and the wiring schematic from Arnott.
Customer: replied 5 months ago.
Also I am trying to think of reasons why the compressor would run nonstop. 1) wiring is incorrect 2) massive air leak- soap tested and no such issue 3) bad leveler - tested and have no difference 4) bad compressor- internal wiring issue causing constant power - possible 5) bad pressure valve - tested separate known good valve 6) bad ecm - replaced with known good unit. What am I missing ? Maybe a bad relay or fuse buy I have replaced both fuses and the relay 2x
Customer: replied 5 months ago.
any thoughts?
Expert:  Wayne Crawford replied 5 months ago.

Sorry for some reason I didnt get a notice of your reply yesterday. Give me a moment to look this over.

Expert:  Wayne Crawford replied 5 months ago.

I can not tell whats what by comparing the pictures really. Can you tell me what wire out of the compressor goes to what pin of the factory connector? Im about to the point of asking you to send me the compressor for testing. LOL

Customer: replied 5 months ago.
The president of Arnott called me today as I sent an email over last week indicating I have had their compressor for over a year and still not able to make it work properly. I spent 20-30 minutes talking to him and the conclusion was he had never heard of my issue. One thought was that the hot leg of the main RTD fuse may have melted against another power supply somewhere and that was creating the constant power supply. He also confirmed that if one or both of the levelers were faulty that the compressor would continue to run. I have removed the levelers from the frame and tested each from a standpoint of raising to a certain point even tested both removed at the same time and individually and found no difference.It is possible they are bad and the new/used ones I bought are bad. He offered to replace the compressor and I said that I would test the wiring further and see if there was a smoking gun somewhere. Not sure what else I can offer as I am now starting to replace the parts I have already replaced. Backyard mechanic 101= replace broken parts with more broken parts
Expert:  Wayne Crawford replied 5 months ago.

My brain isnt in it tonight. Its been a long day. Let me give you a fresh take on my experience in the morning. Im running out of things to have you do or test and its not making sense but Im sure theres something Im missing.

And working with limited tools does make things harder but this one isnt really that complicated. Ive walked people through many, many much harder things before. Im not sure what Im missing here but I will figure it out hopefully after a good night sleep.

Customer: replied 5 months ago.
Ok thanks let me know when you have fresh eyes.
Expert:  Wayne Crawford replied 5 months ago.

OK rereading this I still dont see where you have had it checked for codes. Have you? Its possible Im missing it. Its a long question.

Customer: replied 5 months ago.
I have scanned and checked for suspension codes using GM specific software (not OBDII) and none are showing or are in the history. I can run additional tests for each of the suspension components however all will take a few minutes each as you know and my concern is that if I leave the plug and fuse connected the compressor continues to run while I am trying to the test the individual components. Any thoughts on how to trick the system while leaving everything plugged in?
Expert:  Wayne Crawford replied 5 months ago.

It doesnt put out enough pressure to cause any damage in a few minutes. Go ahead and run the tests. Just give it a few minutes in between each test for the compressor to cool. If the compressor seems to be getting hot throw a box fan on it or something to help cool it.