Help several problems with 2000 XJ

Airbag... probably more of the clock spring (electrical connection) in the steering wheel rather than a bad airbag. Never had to fix it, can't help you there.

Whistle sound... Could be part of the vacuum system, a bunch of small hoses around the engine compartment and a small canister behind the passenger corner of the bumper. Try getting some smoke around the engine compartment and see how it travels. Might see it get sucked into a crack somewhere.

Vibration could be almost anything. Is it lifted? Could be bad driveshaft angle or worn out ujoints. Could also be axle wrap if your rear springs are shot, causing the axle to twist and increase the ujoint angle past the working range.

No shift could be a bad throttle position sensor (TPS). When that fails, most brands will lock in "wide open" position, so the computer thinks you're at full-throttle and won't shift until the rpms hit the redline, for maximum power. Unplug that sensor and see what happens, it's a black sensor pointing at the drivers seat. https://w05.dealerconnect.chry…ceInfo/en_US/80524e3c.gif If that doesn't work, it might be something in the transmission, maybe try shifting to "3" instead of "D" to see if that helps? If you're in "1-2", it'll do the same rev to full throttle before shifting out of first into second gear, but it should still shift eventually. It's certainly worth replacing the TPS along with the idle air control motor on an older Jeep if they haven't been replaced in a while, also take off the intake hose and see how dirty the valve and idle inlet are. If it's covered in gunk, it can affect the idle and low-throttle performance.

"No Bus" happens when you have the key in "on" too long without actually starting it. I don't know if that'll happen in "ACC" or not, but I don't think it should. That just means that the dash is expecting data from the computer and isn't getting it. It's only a problem if the engine is running, and usually means that the connectors are dirty, doesn't affect driving, just the dash.

The whistle is definitely vacuum related. From what you described, it whistles when vacuum is high. I'm not sure about your transmission, but many automatics use a vacuum modulator as part of the shifting controls. A leaking vacuum line would change the signal that the transmission receives and mess up the shifting. I would find and fix the vacuum leak first, then reevaluate the other problems. The vibration might be caused by the transmission not shifting properly.

Does your horn work? I did not see mention of that.

If your horn does not work, the always-on airbag light is conclusively diagnosed as a bad clockspring. The clockspring is a connection for anything electrical on your steering wheel (airbag, horn, cruise control). If your clockspring is bad, the horn will not work because it is essentially disconnected, and the airbag light is on because your airbag is disconnected from the computer.

If your horn works, I have no clue.

Hope this helps.

Fyi, His trans is an aw4 which is all electronic.

Your trans is all electronic there are no vacuum hose going to it. There for a vacuum leak can not directly effect the trans shifting.

Sounds like a good time for a code reader. I guess there is no vacuum modulator, but I would still fix the vacuum leak first and go from there. The electronic controls may use input from a MAP sensor or other sensors that are vacuum affected. Also, a vacuum leak can cause misfiring which would have an effect on throttle position vs. power available, and the computer is set for shifting a perfectly healthy engine, not one with a misfire. I think there may be a TV cable on that transmission also. If so, check that it is adjusted properly.
That's what I like about my Turbo 400, one vacuum line and you're good to go!

Quote from XJfisher09

I do however get vibrations underneath still when heavy on gas I bet it has to do with the leaf springs being shot.

Saggy rear ends are very common with XJs. I think it highly unlikely that saggy leafs would be the direct cause of vibes.

More information is needed for anyone on a forum to help with a diagnosis without seeing the vehicle.

Why do you suspect the leaf springs? Do the vibrations seem to be emanating from the rear of the Jeep?

Does the steering wheel shimmy? Or is the body vibrating?

If the vibrations are, in fact, occurring only under heavy acceleration, then I would suspect it is a driveline issue and not suspension.

It is altogether possible that some axle wrap might be occurring because of the old, tired leafs. Over time, axle wrap can kill driveshaft u-joints, transfer case output shaft bearings, or differential pinion bearings, all of which could cause vibrations.

I vibe under acceleration is usually a driveshaft joint or bad driveshaft angle.

Yes ther is a tv cable on an aw4 so u may have to youtube how to adjust it.

I agree with John on the vibration, hard to tell at this point. I usually try to fix the obvious first, then hopefully build up good vehicle karma to be able to figure out the harder part. Replace anything with excessive play and see how it goes! Saggy springs shouldn't cause a vibration, but could allow a smaller vibration to seem bigger. The vibration might have caused the saggy springs in the first place.

Quote from WILLYN

The vibration might have caused the saggy springs in the first place.

It being an XJ caused the saggy springs in the first place.

A bad ujoint shouldn't affect the transmission shifting. With the parking brake on (test it!) and parked on level ground, put the Jeep in neutral (have somebody else step on the brake if you can) and try to shake the driveshafts. There shouldn't be any play in the shafts and certainly shouldn't be able to hear anything rattle or "thunk". Those are signs of a badly worn out ujoint or slip joint (the splined section of the shaft), but you can tell by watching the shaft where the problem is coming from. There are times when you'll have vibrations from a shaft with no play. That's usually from the driveshaft angles being off from a lift kit or axle twisted from destroyed springs, if your springs still look "ok", then that won't be the problem.

A bad enough vacuum leak could set off a check engine light, but not on its own... it'd be a chain reaction from something else not working correctly. Most parts stores like Advance Auto can scan the codes for you for free. If you were closer, I'd scan them for you myself, but Dover is a little far for me. This should have really been one of your first things to check, so you aren't blindly replacing parts.