Ford LLS air suspension control module characteristics, inputs, & outputs
 

Ford LLS air suspension control module (p/n YU7Z14B205AA), for a 99-03 Expedition 4x4 system:

- Does anybody know the performance characteristics or logic pattern of this module wrt compressor control? ie. What is the 'compressor time-out' feature and what is the designed duration?

- Does the LLS control module actually send an electric signal to tell the compressor to operate it's internal vent solenoid or is that a mechanical feature of the compressor?

- In all cases where a 'CHK SUSP' light comes on, does that mean it always shuts off the compressor and will not come back on until it is reset?

- Does opening and closing the driver's door 'reset' the 'CHK SUSP' light the same way that restarting the engine or cycling the compressor service cut off switch does?

- Where is the 'steering wheel rotation sensor' and 'brake pedal position switch' located? Are these sensors known to fail?

- To remove the LLS control module, the manual says to 'Remove the instrument panel cluster panel' - how is that done? The module is mounted directly over the radio. What else do you have to remove besides the front radio/hvac control trim panel to get at the LLS control module?

Ford LLS air suspension control module (p/n YU7Z14B205AA), for a 99-03 Expedition 4x4 system:

- Does anybody know the performance characteristics or logic pattern of this module wrt compressor control? ie. What is the 'compressor time-out' feature and what is the designed duration?

The basic operation is:
The control module reads inputs from the wheel speed sensors, door latch switches and other sensors (I don't have the manual handy) and controls the compressor, spring solenoids and vent solenoid to keep the vehicle at a pre determined height.
The logic sequence is thoroughly outlined in the service manual.

The compressor Time Out feature is to protect the compressor in the event of a leak in the system. The compressor has a fairly short duty cycle and is not designed to "keep up" with a leak. I can't say exactly what the spec is, but the time out interval is about 1-2 minutes. If the vehicle doesn't reach trim height in that time, the module disables the compressor and illuminates the suspension warning lamp.

- Does the LLS control module actually send an electric signal to tell the compressor to operate it's internal vent solenoid or is that a mechanical feature of the compressor?

The control module controls the vent valve. It is electrically separate from the compressor.

- In all cases where a 'CHK SUSP' light comes on, does that mean it always shuts off the compressor and will not come back on until it is reset?

Yes.

- Does opening and closing the driver's door 'reset' the 'CHK SUSP' light the same way that restarting the engine or cycling the compressor service cut off switch does?

No. The drivers door switch only tells the module if the door is open or closed. This is to prevent the system from venting or filling while the door is open.

- Where is the 'steering wheel rotation sensor' and 'brake pedal position switch' located? Are these sensors known to fail?

The steering wheel rotation sensor is on the base of the steering column. It "reads" a notched ring on the steering shaft.
The Brake Pedal Position Sensor is the brake lamp switch, mounted near the brake pedal shaft.
The rotation sensor is not known to fail very often at all, I've never seen one fail. Brake switches do fail occasionally, as indicated by the brake lamps being inoperative.

- To remove the LLS control module, the manual says to 'Remove the instrument panel cluster panel' - how is that done? The module is mounted directly over the radio. What else do you have to remove besides the front radio/hvac control trim panel to get at the LLS control module?

For this information, you really should source a factory shop manual. There is very seldom any reason to remove the module, they rarely fail.

Hope this helps.

This is great, thanks
 

Awesome reply, on all accounts; I do have the 2 volume factory service manual and will recheck the circuits/components there, but this does fill in a lot of information. Thanks!