I have a stored code for level control exhaust valve circuit. Has anyone ever seen this fault or replaced this valve? Any info would be great. A diagram of the system would be helpful. I was looking into purchasing the factory H2 manuals but they want crazy money for them. thanks

 

Found this link on the subject which is very useful.

The AS ECU Module monitors the current drawn by the valve, the exhaust valve connects to Pin 1 (Hi Side) and pin 24 (Lo Side) of the ECU module (24 pin connector)

The ECU internally switches pin 1 to +12V (Batt) whenever it needs operate the exhaust valve. Pin 24 internally grounds the other side of the exhaust coil via a 0.05 Ohm resistor, the ECU monitors the voltage drop across it and determines how much current the valve is using.

So no voltage drop = Open Circuit, a high drop = over current or short circuit (the coild should pull around 0.65A max)

The Exhaust Valve connects directly to a blue 4-Way connector pins 2 and 3 (only 2 pins used) which in turn links to the ECU pins 1 and 24. The valve should measure around 20.5 Ohms on the ECU connector, if not check the wiring (see attached PDF)

According to the diagrams the AS Relay is also grounds via ECU (to either pin 23 or 24) its unclear if the ECU also montors the AS relay current, it might well do so check the relay (see attached for location)

My guess there's a bad connection somewhere or worst case a bad exhaust solenoid.

Good luck, keep us posted

 

Nice thank you very much. I'll keep you posted. I've only seen the service air suspension light once, but I haven't had the truck very long.