help troubleshooting automatic level control

[sheila]

I have a 2001 aurora.
I have replaced the shocks.
The compressor only comes on for 3 seconds when the car is selected to start.
I have checked the compressor it will run continuously with power connected to the black wire and the green black wire.
The pressure relief solinod will click and relief pressure for a couple of seconds when I connect power directly to the two white wires.
I have checked for leaks and the system seems to be tight.
I have removed the sensor arm and moved the sensor up and down the pump does not come on no matter were the sensor arm is moved or if the air hoses are connected or disconnected.
The manual wants me to connect a code reader to the system and do a bunch of tests. I don't have a code reader and was hoping someone has a troubleshooting procedure that doesn't require a code reader.
All help is appreciated.

[sall]

Sounds like a bad level sensor.

[tigger]

Yup.

[sheila]

Is there a way to confirm that the sensor is defective, before I replace it. Do you know the part number for the sensor?
Thanks for the input.

[tigger]

I'll have to look up the plug pinout...

Part # is GM25728489, but I'd go with a salvage yard part, new is around $200 IIRC. The 2000-2005 Cadillac Seville/Deville, Buick LeSabre, and Pontiac Bonneville all use the same sensor as the Aurora.

[tigger]

Here are the pinouts and wiring diagram.

[sheila]

Thanks for the part number.
Thanks for the wiring info. I have a manual but I was hoping some one had a check for the sensor that didn't require the scan tool. Example what is the internal resistance reading of a good sensor between pin a and c? Does it change with the angle of the arm? If I back pin the sensor with power on what voltages should I expect to see at a,b and c?
The car is in the garage for the winter, I only drive it during the summer months. The scrap yards are covered with several feet of snow and I love the wx in California so I am not motivated to go to the scrap yard till spring.

[awehlage]

OP, I was in the same situation as you were with trying to figure out which ELC component was making my rear end sit super high. Came to the conclusion it was the ELC sensor. Tried cracking it open to look for damage. Finally I just bit the bullet and ordered a used ELC sensor from eBay. Fixed the problem immediately.

www.ebay.com/ulk/itm/281517849899

[sheila]

I have ordered a replacement sensor. It is coming by mail form the USA. It will take about three weeks to get here. I will report back to this post after I have installed and confirmed my system is operational. See you in three weeks.

[tigger]

Jan 16, 2016 0:14:53 GMT -6 sheila said:

...I was hoping some one had a check for the sensor that didn't require the scan tool. Example what is the internal resistance reading of a good sensor between pin a and c? Does it change with the angle of the arm? If I back pin the sensor with power on what voltages should I expect to see at a,b and c/

It's a potentiometer. Resistance should be constant between A and C, the "ends". Resistance between A and B varies with the position of the sensor arm, the "wiper".

More importantly here, with the RIM providing power at pin A (5V ref) and ground at pin C (low ref), it's a voltage divider. The signal from pin B will vary from 0 to +5V based on the position of the sensor arm. The RIM (and PCM) use this value to determine whether to ground the power circuit or the exhaust circuit to the compressor.

[sheila]

Sensor installed system operation seems to be normal. Thanks for the help.