Fault Finding

Information

The fault memory in the PIWIS Tester must always be read out first. Fault codes must be cleared using guided fault finding.

Symptom	Fault detection	Possible causes	Solution
Gradual loss of pressure Vehicle lying to one side after a long time Longer than average regulating times No reaction to driver's request Fault memory Lift time exceeded Leak in pressure accumulator	Check vehicle height over a long period of time and find the leak using leak detection spray	Leak in air-spring strut/air suspension bellows	Replace front air-spring strut > 433019 REMOVING AND INSTALLING FRONT AIR-SPRING STRUT Replace rear air suspension bellows > 434319 REMOVING AND INSTALLING AIR SUSPENSION BELLOWS
		Leak in air lines/valve unit	Check connections, check insertion depth of air lines (colour marking), replace air line
Vehicle lying to one side No leaks in the system	Perform guided fault finding using the PIWIS Tester	Level sensor faulty	Replace front level sensor > 431819 REMOVING AND INSTALLING FRONT LEVEL SENSOR Replace rear level sensor > 431919 REMOVING AND INSTALLING REAR LEVEL SENSOR
		Level sensor linkage/holder bent
		Sensor for body not installed/screwed correctly	Visual inspection of all sensors for body
Vehicle is too high Vehicle cannot be lowered	1. Check air line/line routing	Air line blocked, kinked/frozen	Replace kinked air lines; carefully clean frozen/blocked air lines using compressed air
	2. Valve unit blocked	Dirt in valve unit	Replace valve unit > 432319 REMOVING AND INSTALLING VALVE UNIT
	3. Compressor/valve block blocked	Dirt in compressor/valve block	Replace compressor > 431519 REMOVING AND INSTALLING COMPRESSOR
	4. Perform guided fault finding using the PIWIS Tester	Check vehicle electrical system relays/plug contacts/wiring harness/fuses Drain valve in compressor faulty/leaking/open Drain valve in compressor/control valves in valve block do not work Valve unit does not work
	5. If no problems were found in Step 5: Compressor is faulty	Compressor faulty
Vehicle is too low Vehicle cannot be raised or can only be raised very slowly	2. Check air line/line routing	Air line blocked, kinked/frozen	Replace kinked air lines; carefully clean frozen/blocked air lines using compressed air
	3. Valve unit blocked	Dirt in valve unit	Replace valve unit > 432319 REMOVING AND INSTALLING VALVE UNIT
	4. Compressor/valve block blocked	Dirt in compressor/valve block	Replace compressor > 431519 REMOVING AND INSTALLING COMPRESSOR
	5. Perform guided fault finding using the PIWIS Tester	Check vehicle electrical system relays/plug contacts/wiring harness/fuses Drain valve in compressor faulty/leaking/open Drain valve in compressor/control valves in valve block do not work
	6. If no problems were found in Step 5: Compressor is faulty	Compressor faulty
Rapid loss of pressure	Vehicle lying to the left or right; when you try to switch to a different level, you can hear air coming from the faulty air spring	Air-spring strut/air suspension bellows faulty	Replace front air-spring strut > 433019 REMOVING AND INSTALLING FRONT AIR-SPRING STRUT Replace rear air suspension bellows > 434319 REMOVING AND INSTALLING AIR SUSPENSION BELLOWS
Rapid loss of pressure		Air line torn off	Repair air line > 438541 REPAIRING PRESSURE HOSE
Insufficient damping	Test drive: Adjust the damping level while driving. You should feel a significant change in the damping effect when driving on uneven road surfaces. Also check for hard "knocks" (rumbling noises).	Electric connector for PASM faulty	Check electric connector for PASM and replace it if necessary
		Damping adjustment valve faulty	Replace front air-spring strut > 433019 REMOVING AND INSTALLING FRONT AIR-SPRING STRUT Clean front air lines Replace rear shock absorber > 429319 REMOVING AND INSTALLING REAR SHOCK ABSORBER
		Shock absorber worn or oil leak