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530iT Continued…
I am having trouble with “New Doug,” my 2001 525iT auto, turned 530iT five-speed.
A little background: The chassis has 155k miles on it and the 3.0 with five-speed was installed about three years ago. As I am keeping up with maintenance, I replaced all the control arms and tie rods a few weeks back. I made a mistake while reinstalling the auto level sensors in the rear and one of them was installed backwards. When I got it back on the ground, the air suspension did not inflate correctly (it was leaning and the SLS light was on). Once I realized what I did, I reinstalled it and brought it in for an alignment. Everything went well and the car drove amazingly well… for two days. My wife picked me up in it and it was sagging like a low rider. The bags were completely deflated. Thankfully, it was not a long ride home. Here is where it gets interesting.
I grabbed my Foxwell to scan the sensors and module, etc., and there was no power to the OBD port. It worked great two weeks ago when I reset everything before the alignment. I tried the scanner in another car, and it works fine so now I have a car squatting like a cat ready to pounce and no way to diagnose it. Here is what I have checked so far:
- I started with fuses. Everything in the glove box was good, as were all of them in the trunk. I even replaced a couple that were a little long in tooth, with no luck. Then I went to the OBD port, thinking that once that is good, I can reinflate the bags. All wires are connected, but there is no power to the wire going into the port. The battery has a full charge (it is on a battery tender as I type).
- I thought maybe it was the module in the back causing issues with the OBD, so I pulled the module and rechecked the OBD while it was disconnected. The SLS light came on (expected) but no OBD power. I reconnected it, SLS light goes off, no OBD power, no airbags, and the compressor does not kick on.
- I jacked up the car a bit in case the sensors were beyond their limits (something I read about online) hoping it would recognize it…nope.
- I pulled the compressor. There is power going into the relay but not out. I jumped the connection and the compressor works. Bad relay? Or does the module control this?
- While the compressor was running, the bags did not inflate. Again, this makes me think the module is preventing the air from getting to the bags. The bags were replaced about two years ago, and I guess it is possible they are leaking, but that would not account for the lack of compressor coming on or inflating at all (I think…)
- I read that there are fuses under the carpet on the passenger side so I pulled the carpet and checked those. All had power on both sides indicating good.
- I did not check the box in front of those fuses that apparently has a power connection to the OBD. I learned about that after I reinstalled everything. I will get to that soon depending upon what you suggest after this novel. Here’s the video:
Right now, I am leaning toward getting a replacement SLS module and relay, but before I fire the parts cannon, is there a way to test the module? Are these two items (OBD and SLS) related? Could the module have fried something else? I am stuck! Thank you for any help you can give.
Bryan in San Antonio
Yes, the OBD has its own power which you should check. You are going to have to start here before looking at other fuses and relays as they will not have influence over your current issue. OBD and SLS are not “related,” therefore a failure on the SLS system does not bring down OBD communication.
In regards to the air bag system, you will need to get a fault scan done to see what faults you have before you can start condemning other parts. It is possible you are dealing with a bad relay or module, or even a compressor. Can your scan tool command components? Meaning can it turn on the compressor to see if it works? This will ensure the relay and module are in fact working. I do not think you have an airbag leak; I think the compressor is not coming on when told or poor air pressure output and therefore the rear sags. This could be anything from the relay, the module and/or the compressor.
Try to keep the weight of the car off the sagging airbags to prevent them from being damaged. Seen this a lot on X5s back in the day.
I’m back with partial success, but I’m stuck again. After tearing the car apart, I remembered I had the Bentley manual and dug into the schematics. Fuse 25 (labeled in the car for the radio) was listed as the OBD2 fuse in the Bentley. It looked good, but I replaced it anyway. Success. I assumed it was my eyes getting old, but my kids said it looked good, too. Go figure.
Now to the original problem, my air suspension. I replaced rear suspension components (control arms, etc.,), and now the car squats and won’t raise when powered on. I pulled out the Foxwell and using manual controls, it raises, so the compressor is good. I tried to set the ride height with measurements, but it won’t hold. I don’t think it’s a leak because I can raise the rear axle, pull the key, and it holds for hours. The sensors test good; the valves test good…so I replaced the module with one from eBay.
Still no success. I tried using INPA for the first time, which others say works better. I got the computer talking to the car, and it manually raises, too…but it won’t hold the settings.
What next? The physical components test good, but there’s something in a computer somewhere that doesn’t like the setup. I love the car but I’m on the verge of driving it off a cliff! Help!
(And a follow up before any recommendations were made)
Reason #7,593,612 not to believe everything you read on the internet. I probably read it wrong, but regardless, I have achieved success!
I thought through everything I did going back to square one. Initially I installed one of the ride height sensors backwards, so I fixed that, then went through the OBD2 issue, and down some rabbit holes. One of the sensors checked bad last week as I was diagnosing, so I thought maybe that was the main issue and replaced both. No change. Maybe my Foxwell can’t handle it, so I installed INPA. Still nothing, so I decided to look at the sensors again. I swear, everything online said to point the arm outward, so I did…but they didn’t say WHICH arm. I pointed the connecting arm (not the sensor arm) outward. As I looked at it, I realized that the sensor arm was at its limit and wouldn’t really move with the motion of the car with how I had it installed. A five-minute swap (after my floor jack died, of course…it’s been a rough week!) and everything seems to be working now. With any luck, you won’t hear about this issue from me again!