'18 Rear suspension height sensor - testing specifications?

A pocket scanner isn't going to be able to read or diagnose "C" related DTCs.
With the rear end of the truck sagging, unbolt the lower arm of the height sensor from the coil bucket. Turn it counter-clockwise, a revolution or two in order to extend that lower arm. Bolt it back on and start the truck. If the compressor turns on and raises the rear end, the height sensor is doing its job. Now if it starts losing air and begins to sag, check for any leaks on where the air lines connect to the shocks and compressor with a soap+water solution. If that checks out, highly likely the compressor is the problem which isn't anything new. Nissan is still using the same compressor since 2004. I know because I've already swapped out the air leveling compressor on my QX80 using a compressor being sold for the first gen trucks (saved almost $200). All I did was remove the new compressor from its bracket and installed it on the bracket on my QX80; same with the inline air filter.

primoV8 said:

A pocket scanner isn't going to be able to read or diagnose "C" related DTCs.
With the rear end of the truck sagging, unbolt the lower arm of the height sensor from the coil bucket. Turn it counter-clockwise, a revolution or two in order to extend that lower arm. Bolt it back on and start the truck. If the compressor turns on and raises the rear end, the height sensor is doing its job. Now if it starts losing air and begins to sag, check for any leaks on where the air lines connect to the shocks and compressor with a soap+water solution. If that checks out, highly likely the compressor is the problem which isn't anything new. Nissan is still using the same compressor since 2004. I know because I've already swapped out the air leveling compressor on my QX80 using a compressor being sold for the first gen trucks (saved almost $200). All I did was remove the new compressor from its bracket and installed it on the bracket on my QX80; same with the inline air filter.

Click to expand...

Sorry for the late reply. Understood on not being able to read those types of codes with a basic reader.

I know the compressor works because when I jumper the spot in the relay area I hear the compressor come on and the truck lifts up. I've had the relay unplugged and the height sensor unplugged for about a week and only now has it lowered to a level I'd consider giving it another pump up manually so i don't think I have acute air leaking.

I know the exhaust solenoid works because after pumping up the bags by jumpering the relay, the on board controller must have sensed (before I unplugged the sensor for a while) that it was too high and lowered it down, I saw this happen with my eyes and heard what must have been the solenoid when the truck was lowering.

The only test I didn't do was change the sensor arm position manually while the truck was running and wait 30 seconds (this procedure seems important after reading here and watching some youtube videos) and see if the truck did anything.

When testing terminals on the height sensor I get different resistance readings based on the arm position so it seems to be doing its job to a degree but without specs to test against I don't know if those resistance levels are proper. I bought a new sensor and when it arrives I'll swap out and see if this fixes the system.

Thanks again for your reply. I'll report back on this post once I ultimately figure out the issue.

primoV8 said:

A pocket scanner isn't going to be able to read or diagnose "C" related DTCs.
With the rear end of the truck sagging, unbolt the lower arm of the height sensor from the coil bucket. Turn it counter-clockwise, a revolution or two in order to extend that lower arm. Bolt it back on and start the truck. If the compressor turns on and raises the rear end, the height sensor is doing its job. Now if it starts losing air and begins to sag, check for any leaks on where the air lines connect to the shocks and compressor with a soap+water solution. If that checks out, highly likely the compressor is the problem which isn't anything new. Nissan is still using the same compressor since 2004. I know because I've already swapped out the air leveling compressor on my QX80 using a compressor being sold for the first gen trucks (saved almost $200). All I did was remove the new compressor from its bracket and installed it on the bracket on my QX80; same with the inline air filter.

Click to expand...

I did a test after my previous reply based on procedures I found at this site: https://www.nicoclub.com/nissan-service-manuals. The 2005 had the RSU section which I crossed my fingers wasn't functionally different than for my 2018. It was good enough, even the wire colors seemed the same. On page RSU-18 it describes a testing procedure for the sensor, my sensor passed test 4.3 and 4.4. I didn't bother with test 5.1 since I didn't yet want to go to the trouble of pulling panels to get to the suspension control unit. I moved on to test 5.2 for ground continuity on pin 2, and it did have continuity which should not be the case. I'm still sort of unsure how this tests the sensor but oh well. I got the new ride height sensor in the mail, installed it and it fixed the problem. The whole system now functions normally.