Air ride problems '99 Silhouette

Anonymous wrote the right answer.

Anonymous Jan 02, 2022

What kind of scan tool ? Will it scan all the modules on the vehicle or is it just OBD2 type ? Did you check wiring diagrams an test electrical circuits for air ride an test with a DVOM - digital volt ohmmeter ? Do you know how to test ALC relay circuits . You replaced a bunch of parts that probably were not needed (,air ride compressor, fuses and ALC relay and the compressor still won't work ) ?

Which of these does your vehicle have

Automatic Level Control
Electronic Suspension Control (ESC)
The vehicles rear leveling compressor motor is switched on and off via a compressor motor relay which is controlled by the suspension control module. The suspension control module provides a switched path to ground whenever compressor activity is required. The suspension control module continually monitors the compressor motor relay circuitry to determine if the voltage level agrees with the commanded state.

DTC C0655 Level Control Compressor Circuit

DTC C0660 Level Control Exhaust Valve Circuit

The exhaust solenoid valve is switched on and off via the suspension control module. The suspension control module provides a switched path to ground whenever exhaust activity is required and during a compressor "head-relief" sequence which occurs at compressor start-up if system pressure is lower than 68.95 kPa (10 psi). The suspension control module continually monitors the exhaust solenoid valve circuitry to determine if the voltage level agrees with the commanded state.

DTC C0711 Level Control Air Pressure Sensor Circuit

Circuit Description
The suspension control module uses a 5-volt analog air pressure sensor to determine the amount of air pressure in the automatic level control (ALC ) system. The valid signal voltage range of the sensor is 0.15-4.85 volts. The sensor signal voltage will increase and decrease within the valid voltage range as system pressure increases and decreases.


Your best bet ,take it to a qualified repair shop that knows what they are doing .

This could be a few things that I know of. The rear air shocks compressor could be the problem. If the car was on a car lift with the wheels not flat on a ramp (like hanging) and the compressor was not shut off it can burn up the compressor for the ride sensing etc will try to level the ride but can't. or the thing just went bad. or maybe you have a bad fuse. or you developed a leak in the air bag inside the shock. or the air suppling tubes are loose or bad cracked??? but here is a start good luck mine are out and its costly to have fixed!!!!!! I'm looking to just put on a plain pair of air shocks and by passing the ride sensing etc..... due to cost. IDK but good luck!!

Check the bleed port on the controller, it may be plugged with dirt. or the controller may have failed. A full funtion scanner would help find the problem.
An other option is to by-pass the auto- leveling system and install a manual scrader valve in the air line, this would allow you to add and remove air with any source. They are availble at most autopart stores.

Air ride suspension basically works like this. you have a small air compressor and a sensor that connects between the rear axle and the under body Frame. When this sensor detects a load movement like more or less weight it turns on the air compressor to air up or opens a exhaust valve to let air out. most common problems with this system. broken or disconnected sensor. leak in the air lines between compressor and shocks. or a bad or weak compressor.

you can pull the fuses, but it is hard wired so it might have relays that need to be pulled, or you can just fix it, and replace the air shocks/struts with regular shocks/struts

The simple solution is to pull the fuse for the compressor.

If you want this fixed, you most likely have a leak and will need to find and fix it. The compressor may also be rebuilding. Probably not going to be worth putting the money into fixing.

If you have better than average skills you sould be able to tackle it. You will have to remove 3 nuts from the top and 2 bolts on the bottom. Yo will also need a coil spring compressor that you can borrow from parts store (autozone). The most dangerous part is the spring coming lose but its fairly easy t do in your driveway with regular hand tools.

the egr valve.exhaust gas return.
i would also clean the throttle body

USE THIS LINK http://sumanual.com/instrucciones-guia-manual/OLDSMOBILE/SILHOUETTE%201999-_E

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