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I have an 06 Infiniti QX56. I noticed the rear was sagging, and couldn't tell if the compressor was working. I watched YouTube videos, and looked up forums, I had changed out the suspension relay behind the battery, I changed out the rear shock absorbers, I tested the air ride sensor, and try to bypass it, then I just now replaced the compressor itself. When I pulled out the lines, air pressure was released, plugged in the new air compressor, and it still did nothing. What am I missing, or what else could it be?
 

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When you bypassed the level sensor did the compressor come on? Besides that relay have you checked other fuses and make sure there is current to all relays and the motor?

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When I bypassed the sensor, the compressor did not kick on. I did not check the fuses, I will do that tomorrow, and check the fuse link as well. I've seen some models or maybe just armadas have 2 suspension relays on the passenger fender, but I did not see a second one on my QX56.
 

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Sounds like the compressor may not be getting power then. Check what you stated and see if it's not missing the second relay.

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So I checked the fuses, specifically No.29 Suspension control unit, that one was still good, and the fusible link G, Compression Motor relay (the fuses still looked to be attached, I couldn't figure out how to pull it out). And then the suspension relay behind the battery on the fender is brand new, and that was the only relay there, I did not see a second one.
 

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So I checked the fuses, specifically No.29 Suspension control unit, that one was still good, and the fusible link G, Compression Motor relay (the fuses still looked to be attached, I couldn't figure out how to pull it out). And then the suspension relay behind the battery on the fender is brand new, and that was the only relay there, I did not see a second one.
Is your truck 4WD?
How did you bypass the ride height sensor?
 

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It's not 4WD. I put three paper clips in the wiring harness connector to the sensor. Followed the steps off of someone from YouTube.
 

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It's not 4WD. I put three paper clips in the wiring harness connector to the sensor. Followed the steps off of someone from YouTube.
If your truck is not 4wd then you only have 1 relay behind the battery. The 2nd would be for the transfer case motor.
I don’t believe you can just jump out the ride height sensor. It gets power from the control module and returns a value of 0-5 volts thru it’s travel. Level is somewhere in between, like 2 volts maybe. So jumping it out may just tell it that the suspension is all the way up. I don’t remember which way is 5 and which is 0. You really need to check it at the control module to make sure it’s working. If you unhook the arm and play with it you may get it to run the pump briefly. If it has any play in the arm on the sensor there’s a good chance it’s bad.
 

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Oh I gotcha. Where is the control module at, is that the one in the back behind by the 3rd row seat, behind the panel, above the rear wheel? I didnt think it would be the sensor, if the compressor isnt getting any power to it.
 

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Oh I gotcha. Where is the control module at, is that the one in the back behind by the 3rd row seat, behind the panel, above the rear wheel? I didnt think it would be the sensor, if the compressor isnt getting any power to it.
The module is in the back where you think. The sensor returns a signal to the module relative to its position. The module either closes the relay to run the pump or opens the relief valve to let air out until it sees the correct voltage that it determines level. So if the sensor is bad the module will never command the pump to run. The sensor is not real expensive and it seams like you’ve replaced almost everything else so far. You may want to just change it as opposed to pulling the back interior out to get to the module. I did the same job last summer on the same truck. ‘06. 175k. Bad ride height sensor.
 

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Discussion Starter #11
I gotcha, well I guess I'll try swap out the sensor first, and see if that works. Then if not, last resort is the module. So wouldn't have bypassing the sensor to see if it's bad, kicked on the compressor then?
 

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I gotcha, well I guess I'll try swap out the sensor first, and see if that works. Then if not, last resort is the module. So wouldn't have bypassing the sensor to see if it's bad, kicked on the compressor then?
Like I said earlier, I don’t think you can just jump out the ride height sensor. It’s not a light switch. It sends a variable voltage signal back to the control unit which is a computer. If you want to take the time to pull things apart you can test it all with a meter. Service manual shows you the pin locations. That will tell you for sure. Just a matter of your time versus your wallet.
 

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Discussion Starter #13
If I replace the height sensor, and it works, do I need to take it somewhere to clear the codes and adjust the sensor from a computer or diagnostic tool?
 

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If I replace the height sensor, and it works, do I need to take it somewhere to clear the codes and adjust the sensor from a computer or diagnostic tool?
No. The sensor is plug and play. Just compare the
If I replace the height sensor, and it works, do I need to take it somewhere to clear the codes and adjust the sensor from a computer or diagnostic tool?
No. The sensor is plug and play. Just compare the Length of the linkage from the old to new and adjust if necessary.
 

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No. The sensor is plug and play. Just compare the

No. The sensor is plug and play. Just compare the Length of the linkage from the old to new and adjust if necessary.
Sweet, I'm ordering the part today, I'll keep you posted on new updates. Thank you!
 

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No. The sensor is plug and play. Just compare the

No. The sensor is plug and play. Just compare the Length of the linkage from the old to new and adjust if necessary.
Hey, so i got the sensor installed, and STILL nothing. Didn't see any difference or hear the compressor kick on. So I'm assuming the last thing is the suspension unit in the rear fender panel by 3rd row seat?
 

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Hey, so i got the sensor installed, and STILL nothing. Didn't see any difference or hear the compressor kick on. So I'm assuming the last thing is the suspension unit in the rear fender panel by 3rd row seat?
Sounds like you’ve changed everything else already. I would recommend doing some testing before you go for the controller. New is pretty pricey and a junkyard unit could be a crapshoot. And it still has to be flashed with the consult scan tool so that’s a trip to the dealer unless your lucky enough to have access to one.
How are you with a meter and do you have a factory service manual.
 

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Discussion Starter #18
I found a used one on ebay for $90. And no I don't have a scan tool. I have some knowledge on a multimeter, I just don't use it. I guess I'll have to, to check for power on some of the connections and the compressor and sensor. I can download the factory manual from google.
 

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I found a used one on ebay for $90. And no I don't have a scan tool. I have some knowledge on a multimeter, I just don't use it. I guess I'll have to, to check for power on some of the connections and the compressor and sensor. I can download the factory manual from google.
I think that is the way to go. If you put a used controller in and it doesn’t solve your problem you still won’t know if it’s a bad part or you have another issue. Dig it out of the back wheel well and go through the test steps in the FSM. Make sure you have power in To the controller and you have the signal out to the sensor. Do all the steps 1 by 1 to narrow it down. You should also be able to run the compressor off a jumper pack to test it if you haven’t already. It could be something as stupid as a broken wire. Good luck.
 

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I think that is the way to go. If you put a used controller in and it doesn’t solve your problem you still won’t know if it’s a bad part or you have another issue. Dig it out of the back wheel well and go through the test steps in the FSM. Make sure you have power in To the controller and you have the signal out to the sensor. Do all the steps 1 by 1 to narrow it down. You should also be able to run the compressor off a jumper pack to test it if you haven’t already. It could be something as stupid as a broken wire. Good luck.
So I tested some of the connectors, specifically the ride height sensor, it was receiving 5 volts from pin 1, and continuity from pin 3. I then tested the connector that goes to the compressor, and it was only putting out 7.35 volts. Just like that guys 48min YouTube video, he saw that his control module was messed as up well, so i think thats what I need to replace. Do I need to take it to a Nissan dealership to have it flashed with the scan tool, or any mechanic shop can do it?
 
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