A 2015 BMW X5 F15 5.0 Petrol 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. Replacing the air bag at that time resolved the issue. However, the recent malfunction caused the rear of the vehicle to remain raised in a fixed position.
BMW agents initially replaced both rear height sensors, but the error persisted. Their recommendation to replace the air compressor at a significant cost prompted the owner to seek assistance from an independent shop. The independent shop serviced the compressor and replaced the compressor discharge valve, restoring the suspension to its normal height and functionality. Despite this, the “Chassis Restriction Malfunction” error remained on the dashboard.
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 indicated a need for height adjustment. However, calibration attempts consistently failed. Measurements revealed discrepancies between the nominal and sensor-determined ride heights:
- Nominal ride height: Rear axle: 724mm, Front axle: 734mm.
- Sensor-determined ride height: Rear left: 524mm, Rear right: 721mm.
Further investigation showed the rear left sensor consistently reading 0, while the rear right sensor displayed approximately -2.0 degrees. This occurred with both new and old sensors. Suspecting a faulty rear left sensor or a signal interruption, the power supply to both rear sensors was checked and found to be just over 5V with the ignition on.
Tracing the signal wire from the rear left sensor proved challenging, as it routed towards the front of the vehicle, rather than the expected EHC module near the rear left fuse box.
The primary question remains: where does the third signal wire from the rear left height sensor terminate? Knowing this would allow for continuity testing and further diagnosis. Has anyone encountered a similar issue with a Bmw D71402 error code and can offer insight into the signal wire routing or potential solutions? Any assistance would be greatly appreciated.
