Land Rover air suspension" Faults & diagnosis " 1995 - 2002 p38 model

"E.A.S FAULT" Message
The "E.A.S FAULT" message is displayed when any number of faults, such as the ones listed below, are detected by the system ECU. As well as the message, all the lights on the height adjustment rocker switch start flashing and eventually settle into staying on, along with the "high" ride height indicator light. There are two degrees of severity of this fault condition:
1. "Hard Fault": If the fault is considered serious, the system goes into what we long-suffering owners call "Hard Fault" mode. It is accompanied by the vehicle lowering itself to the bump stops and displaying the warning not to exceed 35 mph. Even if the cause of the fault is repaired, the hard fault condition cannot be reset without a visit to the dealer or other mechanic with the specialized T4/Test-book, Rovacom or Auto-logic test equipment. Most common causes are serious air leaks or compressor problems.
2. "Soft Fault": This is my own name for the less serious condition when the E.A.S FAULT message appears, accompanied by the Christmas tree lights on the dash, but not the the "25 MPH" warning. The suspension can no longer be moved from the current height, but will continue to run the compressor and make adjustments. In this case you are lucky; if the cause of the fault goes away, the fault clears itself when you switch off the engine for a while and restart it. In my experience and from other reports, The causes of this condition can include a bad E.A.S relay in the engine compartment fuse box, a bad ground somewhere in the E.A.S system, an intermittent electrical connection, or a faulty height sensor.


Frequent Compressor Operation:
Unfortunately this is usually normal. Suspect is the pressure switch being located on the valve block instead of at the tank. This causes the pressure switch to sense a drop in pressure every time air is drawn from the tank -- due to the long narrow gauge airline from tank to valve block. This momentary drop in pressure causes the compressor to come on again. If compressor operation becomes almost continuous, however, something is wrong
Continuous Compressor Operation:
The compressor should shut itself off when it gets hot or when pressure reaches 10 bar (150 psi), but if it seems to remain on too much the first thing to check for is the presence of leaks (see above), most likely from the air tank connection to the valve block. Then, see if either the air compressor relay (Relay 20, Engine Compartment Fuse Box) or the pressure switch is stuck on (see the Electrical Troubleshooting Manual for details). Otherwise, the compressor may be simply worn out -- this does happen. Starting from a completely depressurized tank, the compressor should take about 6 minutes to recharge it. If it stays on long enough to overheat, its thermal switch sends a signal to the ECU which shuts it down for 3 minutes to cool off. 
Frequent Short-Time Ineffective Compressor Operation:
If the pump runs with a short duty cycle, IE runs for a few seconds and stops, without effective pumping action, Its been reported that it is most likely the E.A.S ECU cutting off the pump's power supply die to excessive electrical draw. The computer diagnostic systems often miss this fault. If you pull the pump relay and jumper the 30/51 pin to the 87 pin, the pump will resume running if this is the problem. The most common cause is the failure of the pump's rear bearing. A shortcut for fixing this problem is listed on the Falconworks site, and consists of drilling the brush holder from the rear bell of the motor, so the bearing can be cleaned or replaced and lubed, preloaded and staked back in so it will not shake itself loose again. If you try this, the four brush-holder retainers will need to be drilled on-center and tapped to #4x40 threads. Be sure to touch-up the solder joints on the back of the brush holder that were cracked by the armature flailing around, then refit it with new 4-40 screws. Falconworks advertises the ability to repair your E.A.S pump in this situation for about $100, depending on the level of damage, plus shipping.
Slow Pump-Up after Leaving Overnight:
In theory, even if the unintelligent ECU has lowered the vehicle to the bump stops overnight, the non-return valves in the valve block should ensure that enough air remains in the tank to pump it up again immediately in the morning. If this does not happen, and it takes ages for the system to pump up to normal height in the morning, air is probably leaking from the line from the tank to the valve block (usually at the connection to the valve block). If not, the valves inside the valve block are probably leaking; as of this writing there is no known solution for this other than to replace the $800 valve block.
Noise or Vibration from the Compressor:
After a while the air suspension compressor can get rather noisy due to the rubber mounts wearing out. A Service Bulletin (TEC600695, July 1995, "Electronic Air Suspension Compressor Noisy") recommends updating the compressor mounts with  2 STC 828 Rubber Mounts and 6 STC 3086 snubbing washers. I had this done on my 4.0 and it did quieten down the compressor. The new bushing design is better because it prevents the compressor mounting flanges sagging low enough to hit the mounting surface. Loose mounting nuts, can also lead to noise. Conversely, don't over tighten the nuts as the studs are just embedded in plastic and come loose, again causing vibration. If the noise is a kind of harsh rattle, the compressor is probably worn out and needs replacing or rebuilding.
Compressor Failure:
Complete failure of the compressor could be due to the failure of Fuse 44, Maxi Fuse 2, or Relay 20, all located in the engine compartment fuse box. The easiest way to diagnose the power flow is to unplug relay 20, connect its output socket to 12V and see if the pump runs. If so, the compressor itself is clearly OK, but the problem could be the relay or one of the fuses, the thermal cutout switch, the pressure switch or the ECU. For more compressor diagnostic information see the Compressor Diagnosis and Replacement page.


 Intermittent compressor operation (or only operating for a small fraction of the time, resulting in very slow pump-up of the suspension) can be due to failure of its internal thermal cutout switch, which is designed to shut down the compressor when it gets too hot. In normal operation, the third lead on the compressor (which is internally connected to this switch) is grounded; when overheating, the switch opens. This happened on my 4.0SE; I was able to get the system going again by grounding this lead with a jumper. See the Compressor Diagnosis and Replacement page for more information, and the generic parts sources page for aftermarket replacement compressors.

 
Air Spring Leaks (Slow):
  Rubber air springs do wear out faster than the old coil springs. One symptom is the boot popping out of position, especially in cold weather; I had this happen on leaving the car outside in the desert overnight, in access mode, and the suspension took a good 10 minutes to return to normal height on startup in the morning. The rubber boot seems to mate with the top metal part of the spring somewhat like a tire bead, and will usually reseat itself after a while. One reader pressure tested an old air spring he replaced on his 95 LWB (see replacement procedure); he pumped 20 psi into it and put it into a bucket of water. Air seeped out from the top, between the metal and rubber joint. He tried a higher pressure and it sealed up (the pressure in actual use is up to 20 bar or 150 psi). Another problem is plain old cracks and holes developing in the rubber when it gets worn. This happened on one of my rear springs around 80,000 miles.  I was shocked that the system put up with this situation without shutting down and reverting to the "limp home" mode on the bump stops.

Air Spring Failure (Catastrophic):
Sudden failure of an air spring can occur due to spontaneous bursting or more likely being penetrated by some off road obstacle. If at high speeds the vehicle becomes unstable and can easily overturn.