Originally Posted by TriX5

Mine went on the blink last week. When I turn the ign. key to p2 the TPMS light goes off and then on again. A few seconds later the SLS inactive mssg comes on. Last week I drove off and after a few miles it went off and on Sunday it was fine. On Monday it refused to work at all and the left front starts to sag. (I haven't replaced that bag and that is why it shows there first I guess)

All fuses are fine. I tested the pump by itself and it works. The relay in the fuse box works when tested out of the car. I activated the relay that is mounted to the side of the battery with 12V and the pump comes on fine. Today I took the panel off the passenger side to check the valve block.

There are three connectors on the valve block. Clearly the front one controls the front air supply, the rear one controls the rear axle. The middle connector is a mystery to me. The front valves work fine (the top connector is gnd, the other two are for adding air or releasing air it would appear). I concluded that both front bags are controlled by a single valve. Same must be true for the rear bags. I wonder how L/R balance is achieved? Maybe just the stabilizer bar?
I got interrupted but tomorrow I will test the rear valves.

Before I have the codes read at the dealer I will check the level sensor output on each suspension corner. Any one have thoughts on how to check these sensors?

If the sensors check out ok then I must conclude the fault is the EHC behind the glove box. What I do not understand is why the TPMS light comes on?