Suspension light at highway speeds

Hi All!
When I first started having problems with my car years ago (but after replacing the totally shot front struts,) it started with a suspension light after about 20 miles of highway driving. It's doing it again! After replacing just about everything I started getting the same stupid error on the highway again. The car can sit for a month in the garage and not drop, but I can't drive it 40 miles on the highway! It airs up fine after restarting it and will make it around in town fine (so far).

I have almost new front struts (20K), even newer rear bags (6k at most) Brand new stock compressor and dryer, new (used) suspension computer. What gives? Why would it have a problem on the highway?! I can't believe that the bags are leaking so quickly after replacing them. I'm hoping it may only need a new relay. The current relay was in it before I replaced the brain and compressor and could be questionable. Does it use a lot of voltage during extended highway driving? How do you test a relay?

I also wish I had a way to know when the compressor kicks in. I can't hear at all it when driving. That way I could tell if it's coming on when on the highway.

I had just started getting a little confidence in the car but now I'm almost wishing I could sell it and get something without so many "issues..." ::nono::

RE: Suspension light at highway speeds

i know that when it gets up to a certin speed the M8 lowers itself to make it more airodynamic....... maby that has something to do with it......

RE: Suspension light at highway speeds

When does the light com on? At highway speeds or when you get below 55 mph? As was siad, the car drops at 55 mph for a cruise mode driving. when you slow down, the compressor starts up and brings the car back to standard level. Do you have a service manula? Have you looked and checked the height sensors? Make sure they are connected to the studs and are not just on the outside of them. There are three height sensors. One on each front wheel and one on the rear about in the middle of the car. It would be best if you physically checked them out. One of those also could be bad. Depending on the year, you could always get a scan on the system. There is a connection for a Star II tester. Maybe one of the AutoZones or some place like that will check out your suspension. The connector is under the hood, on the passenger's side right in front of the shock tower on all Mark VIIIs. It is a standard Star II connection with memory and will tell what is wrong with the car'a suspension.

RE: Suspension light at highway speeds

I would suspect the VSS(vehicle speed sensor) or related wiring, since it appears to sit without leaking and raises when first started and otherwise function properly.

You should be able to hear the compressor inflating the system when dropping below the 55/65 mph cut off point. I can tell when mine is doing it when getting off a highway at a short ramp with a stop sign at the end.

Try shutting off the suspension switch AFTER the car is started and has risen to ride height. That should alleviate the concern until you can get the system scanned for DTCs.

RE: Suspension light at highway speeds

"I can tell when mine is doing it when getting off a highway at a short ramp with a stop sign at the end."

I can hear it when stopped but not when moving. It is throwing the light after about 20 miles of steady highway speeds (85mph) without ever slowing down.



"Try shutting off the suspension switch AFTER the car is started and has risen to ride height. That should alleviate the concern until you can get the system scanned for DTCs."

I drove the car this way for months before replacing the computer and compressor this last time. I am pretty knowlegable about the car and how it works, and the fact that it is screwing up when there shouldn't be much going on (steady high speed) is what is confusing me. The struts and bags are so new I can't imagine a leak, plus it doesn't lower at all when parked for an extended period. I suspected the relay because it is the only thing that's not new, but again...if nothing is going on why would it send and error?

Thanks.

RE: Suspension light at highway speeds

Perhaps I misunderstood your initial post. I didn't know it was 20 miles at steady state highway speed and assumed it was malfunctioning at either lowering the car at highway speed or raising the car after lowering the speed. After perusing the manual, the only recourse I know would be a scan for stored codes to isolate the problem.

Air Suspension System General Notes

When the CHECK AIR RIDE message is displayed in the message center, the system error that has been detected by the control module is stored in the module's memory. This diagnostic trouble code will be retained for the next 80 ignition cycles. If there is no repeat of the same error during these 80 ignition cycles, the module will erase the code.

Because of this self-erasing memory, a customer may have had a concern "just a few days ago" that is not retrieved from memory when Function Test 211, "RETRIEVE ALL MEMORY CODES", is executed. This must be kept in mind if you must tell customer that no current condition has been found.

When the control module detects an error, the air suspension system is disabled for the current ignition cycle. If the condition causing the error clears up during the current ignition cycle the system will not reactivate.

For example, if the customer has severely overloaded the luggage compartment, the system will not be able to trim the vehicle without exceeding the compressor run time. This will generate a diagnostic trouble code 98 that disables the suspension system. If the customer then drives the vehicle and unloads the luggage compartment without turning the ignition off the system will not adjust for the new load. The customer will experience poor ride quality and the vehicle will not adjust trim for either high speed or low speed travel.