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I have a 2001 s430, the suspension has dropped and will not come back up. I checked the air pump for the suspension and it is not coming on with key on power. I pulled the wheel and put my power probe to the air pump and with 12v power it comes on so its working. I've checked fuse 32 and the air pump relay which are both good. Out of ideas... Why wont my pump come on?
 

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Beginning with the simplest test solution, make sure the battery is charged up well enough, particularly with adequate cold cranking power. Sometimes, an electronic control unit (ECU), control area network (CANbus) or signal acquisition module (SAM) may not respond properly with the battery at lower power, even if the battery reads a high enough voltage.
Next test, remove the relay and bench test for functionality.
Then, check fuse 32 for continuity.

If all are in order to this point, check the compressor pump with an external 12-volt current source. If the pump works, search for the source of the discontinuity between the ignition source and the pump with a scanner, since there are several sensors that provide input to the airmatic suspension system. There are several affordable scanners on the market for the W220.
 
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