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Hello,
I figured I would jump in on this post to ask a questions since its the most recent technical discussion on the air suspension.
Purchased an 03 with 80k miles back in Dec 22, I had an issue with the suspension losing air over a couple days which ended up being a combo of replacing the original Firestone bags and the o-rings on the solenoid block needing to be replaced. I pulled the whole rear assembly and cleaned it and and got it back to looking like new fairly easy so there was never anything that looking really wrong or worn out.
The issue I have now is most of the time when I turn off the truck and open a door, after driving, ill get this erratic, random clicking that last a few seconds and stops when the doors are closed, almost like a relay with a bad ground. Seems like it wouldnt want to adjust at all with a door open. Otherwise the air suspension acts correctly
Notes:
its done it with different doors opening
pretty sure the truck has to be off
only other weird issue is the factory keyless really doesnt like to unlock passenger door on second press unlock or second press lock to honk the horn on lock (new remote and battery), Not sure the PDM would matter anyway
Idkorcare80 well done for the work you've done so far, it would be good to see some pics 📷
If it's the AS inlet solenoids this could be considered abnormal activity (probably) so here's a couple of points about the AS ECU module:-
Pin12 connects to the "HVAC/ECAS" fuse (underhood fuse box) and is "Hot all the time" so in effect the module it's always powered.
Pin 21 connects to the "4WD"fuse (lower left dash) and is "Hot in Run" (ignition 3) the module uses this signal to detect the engine is running before allowing AS module operations.
From the service manual "The leveling function will be disabled when any door is open or when the inflator is being used. To prevent energizing the electronically controlled air suspension relay or air suspension inlet valves during normal ride motions the air suspension module provides a calibrated delay before leveling the vehicle."
It's as if the AS module thinks the ignition is On when it's not, this being the case there could be a few causes:-
The AS module ignition detection circuitry could have failed internally (low probability) you can check if you have access to a Tech2 scan tool by looking at the AS Ignition detection On/Off status (menu 11)
Something could be back-feeding the Ignition "Hot in Run" line (possibly the windshield wiper motor)
A bad front windshield wiper motor has been known to affect "Hot in Run", this can be checked pulling a couple of fuses, "W/S WASH" (Underhood fuse box) and "WS WPR" (lower left dash)
Also pulling the "4WD" fuse should prevent the AS from running, but this also feeds the "Ride Height" console switch and the "Transfer Case" neutral lamp (theoretically)
Keep us posted 👍
Last edited by oceanbrave; May 20, 2023 at 05:59 PM.
Like I said got it back in December and its really just a spare car, think Im still on my second tank of gas. Been slowly de-chroming and cleaning it but spent a fair amount of time trying to figure out the AS issues. Ill try to video record the issue and report back when I get a chance. Reason I asked about the keyless module is I figured it might tie into the door triggers not only does it not react to second lock or unlock actions consistently I had some issues programming the remotes if they would program at all. Defiantly didnt act the same as all the keyless programing videos and directions showed. Took the PDM completely apart and looks like new inside.
Idkorcare80 your AS unit came-up very nice, good to see.
There is interaction between the BCM, DDM, PDM and AS modules, but this is done by serial communications and not by wiring.
The BCM will inhibit AS operations with any door open and presumably when the engine isn't running.
The PDM has a wideband RF receiver module that detects signals from the Key-Fob transmitter, the pulse pattern are relayed to the BCM, and according to the service manual the keyless system can operate the following:-
• The door locks
• The interior lamps
• The parking lamps
• The headlamps
• The puddle lamps (if equipped)
• The horn
BCM commands to the PDM/DDM control their IC's to turn on/off solenoids and relays and relay back "lock/unlock" and "door ajar" conditions, in effect this no different to manually operating the door lock/unlock switches.
Can't be 100% certain there's isn't a link to the keyless entry system, but it seems very unlikely, the BCM reacts to Key-Fob button-presses, performs whatever job is needed, such as unlock a door, then the job is complete.
It is my understanding that the AS unit is inhibited by hardware detection of the ignition switch status.
(snippet of the AS Module's electronics)
Check if the tire-inflator can only operate only when the engine is running (door open/closed state is irrelevant) the inflator switch LED shows the status.
Other possibilities are communication errors caused by aftermarket equipment, or a bad/weak battery.
Under low battery conditions I have heard my AS relay clicking.
Thanks again for the info. Didnt notice anything odd with the air inflation button but with the issue being intermittent its harder to track down. Probably wait till I take the rear bumper off again so I can test things more easily. When I was cleaning up the solenoid block, I removed both of the solenoids, one of them was harder to remove so I sanded down the post inside so ill probably check it again. Maybe its binding up when engaged.
Idkorcare80 if you are working on the solenoid block, could you take some pictures?
I believe the 03 has an aluminum block as opposed to plastic, so it would be good to get a look inside to compare. In the future it may be necessary to re-manufacture the blocks and aluminum would be the way forward.
Yea it is, if you look at the above pics you can see it. Mine looked great inside and cleaned up good. I be sure to grab alot of pics when I get to it. With the rear bumper off I figured out how to get that block in and out without dropping the whole AS assembly to test different size orings. I think I settled on 5/10 orings. 6/10 leaked and 6/11 also worked. (FWIW my OEM air lines might have been more of the issue with the 6/10 leaking )
