A 2015 BMW X5 F15 with 52,000 kilometers recently displayed a “Chassis Restriction Malfunction” error. The vehicle, equipped with rear air suspension, had a history of sagging on the rear right side approximately a year prior. At that time, the air bag was replaced, resolving the issue.
A few weeks ago, the “Chassis Restriction Malfunction” error reappeared, accompanied by the rear of the vehicle raising to its maximum height and remaining fixed. The vehicle was taken to a BMW dealership where both rear height sensors were replaced. However, this did not rectify the problem. The dealership then proposed replacing the air compressor at a significant cost. Subsequently, the owner took the vehicle to an independent shop, where the compressor was serviced and the discharge valve replaced.
Following this service, the suspension returned to its normal height and appeared to function correctly, eliminating the sagging issue and restoring proper compressor operation. Despite this, the “Chassis Restriction Malfunction” error persisted. Diagnostic tests using ISTA+ revealed the following error codes:
- 480116 – ICM: Carrying out ride height adjustment.
- 480117 – ICM: Carrying out ride height adjustment.
- D354D0 – Signal (filtered vehicle ride height, 52.0.2) invalid, transmitter ICM.
- D71402 – ICM interface (rear left sensor 0xE4): signal invalid.
- D71403 – Ignition control interface (rear right sensor 0xE4): signal invalid.
- E69A41 – ICM interface (ride-height, vehicle, filtered, ID: 0x0E4): signal invalid.
- E6AC64 – ICM interface (ride-height, vehicle, ID: 0x0E4): Signal invalid
These codes suggested the need for a height adjustment. However, multiple calibration attempts proved unsuccessful. Measurements taken revealed the following:
- Nominal ride-level height: Rear axle: 724mm, Front axle: 734mm
- Sensor-determined ride height: Rear left: 524mm, Rear right: 721mm
Further inspection showed the rear left sensor consistently reading 0, while the rear right sensor displayed a reading of approximately -2.0 degrees. This occurred with both the new and old sensors. This points towards a potential issue with the rear left sensor signal, possibly due to a wiring fault.
Both rear sensors received just over 5 volts with the ignition on. Tracing the signal wire from the rear left sensor revealed it leading towards the front of the vehicle, rather than the expected connection to the EHC module near the rear left fuse box.
The current challenge lies in identifying the destination of the third signal wire from the rear left height sensor to perform continuity checks and further diagnostics. Any information regarding the wiring diagram or the signal wire’s routing would be invaluable in resolving this persistent “Chassis Restriction Malfunction” error, specifically related to the D71402 code. Has anyone encountered a similar problem and found a solution?
