Personnel experienced a malfunction of the oshkosh truck corp. All steer all wheel steering system on 2002 pierce manufacturing fire apparatus. At about 45 m h, the rear wheels on the third axle turned out of alignment with the forward direction of the vehicle. This condition made it difficult to maintain control of the vehicle within the confines of a single traffic lane, and could have resulted in a vehicle crash. Mechanic noted that axle locking pins had failed to seat, and had to complete a lengthy sensor...
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adjustment procedure to get the pins to seat. Pierce replaced the wiring harness and sensors. This problem has been the subject of previous recalls(01v113000) (02v294000). Pierce prevoiusly reported 100% completion of the wiring harness recall. Sensor adjustment or replacement of the wiring harness and sensors does not address the underlying issue, and will not prevent further malfunctions. The underlying issue is that the oshkosh system axle alignment sensors only determine that the axles are in alignment to allow the pins to drop. After the pins are released, there is no sensor or other mechanism to ensure that they have seated properly. In the event of malfunction, the system is incapable of detection and subsequent default to a safe condition. The system requires addition of a sensor to ensure that axle locking pins are seated, self diagnostic upgrade with system interlocks allowing default to safe condition in the event of malfunction, and root cause analysis of axle sensor misalignment. *Ak