Porsche Cayenne Air Suspension Fault 1772 Pressure Sensor Signal Abnormal
A Porsche Cayenne 9PA with a mileage of about 162,000 KM and a M55 engine. The vehicle’s air suspension fault light came on when the vehicle was driving on a bumpy road.
According to the customer’s description, no fault was found in the test drive on the bumpy road section. Check with the diagnostic instrument and find that the level control is faulty, and the signal line signal of the pressure sensor is abnormally faulty.
The car is all signaled by the level control unit to the pressure sensor.
Possible causes of failure:
(1) pressure sensor;
(2) air hose;
(3) leakage of compressed air line;
(4) level adjustment control unit failure;
(5) level control unit pin loose;
(6) There is a virtual connection between the horizontal control unit and the middle circuit of the valve group.
Checking the lines from simple to complex, and the lines from the horizontal control unit to the valve group are normal. After dismantling the horizontal control unit, no obvious fault location can be seen, and then check the pins are normal. There are no problems with other components after inspection, so first communicate with the customer to replace the valve manifold. After replacing the valve group, no fault was found in the test run. But within two days, the customer called to say that the air suspension fault light was on again, and then asked the customer to drive back to the factory for inspection. Connect the diagnostic instrument to check that the system fault is stored as the signal line of the horizontal control fault pressure sensor. The signal is abnormal, which is exactly the same as last time. Here comes the problem. After all the inspections have been checked, why is there still such a fault? Replacing the valve block did not solve the problem.
Think about it, is there anything else you haven’t checked? Take another look at how the control functions of the system work:
(1) Lift the vehicle. In order to raise the vehicle, the air springs on the front and rear axles are charged separately, the compressor pumps the air out of the accumulator and leads the air springs through pipes and block valves, for which the switching valve 1 and the corresponding air are switched. Spring switch valve.
(2) Lower the vehicle. In order to lower the vehicle, the air springs on the front and rear axles are switched separately, the compressor pumps air out of the air springs through switching valve 1, and the air is led into the accumulator through the air dryer and switching valve 2, so the circuit design means that the system the moisture will be removed.
Judging by the understanding of the function activation, is the air pump broken? After communicating with the customer, first unscrew the hexagon socket head screw of the rubber seal on the right side of the air pump. As a result, there are many water stains inside. Then, after replacing the air pump, no faults were found in the test drive. Because when the air pump was disassembled to check the intake hose, the air intake was very large, but the exhaust was not very smooth.
Sure enough, a week or so later, the customer called again and said that the fault light came on again one or two hours after he ran the high speed. When he went to the factory to connect the diagnostic instrument, he found that the fault was due to the abnormal signal of the signal line of the pressure sensor.
Where is the difficulty in checking? Or is there something wrong with the horizontal control unit? I consulted a lot of teachers and peers, some said to replace the air pump, some suggested to repair the level control unit, and called to consult experts specializing in repairing the control unit, but the result was that it could not be repaired and suggested to be replaced. The valve group was also replaced, and the air pump was also replaced, but the fault remained the same. Finally, I clarified the thinking and eliminated the related ones one by one. There is another 92A in the repair garage shop with the same control air spring suspension, compare and verify.
When the air pump intake pipe is disassembled to blow air into the pipe or inhale, there is air flow, and it is very large. When blowing air to the same part of the intake pipe of the faulty vehicle, the intake is smooth, but the exhaust is particularly laborious. Could it be the fault here? It turns out that there is something similar to a muffler in the air intake, and the black part in the middle seems to be blocked by something. It is installed in the right front inner lining, and it can be seen after removing the decorative plate on the kettle. Due to the blockage of this part, the compressor exhaust is not very smooth, so it is normal for our short-term test drive.
When the mode is automatically adjusted, the gas cannot be discharged, so the poor exhaust of the intake pipe is the root cause of this failure.
Replace the air pump intake pipe.
At the beginning, I checked the intake pipe, and I could get in, but I wasn’t sure if the intake and outflow were proportional, so I wasn’t sure if the intake pipe was damaged, so I ignored this detail – I could only intake air but the exhaust wasn’t very smooth. Be sure to check carefully, don’t let go of every detail, prefer to spend more time and a little slower, check must be in place, you can avoid a lot of detours.
Although this case is not a big fault, it is a very representative classic case, and it gives people a sense of enlightenment at the end. Through this case, we can see that often we pay more attention to the performance of the failure, while ignoring the composition of the entire system and the working principle of the entire system. When it comes to fault phenomena and maintenance faults, it only pays attention to the local functions associated with the faults, ignoring the overall logic, so it has experienced many repeated maintenance. This is also the biggest lesson that this case brings to us.
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