EA4-x NTC 0x0AA LoaImdtShtdwn

Nexteer Confidential

LOA Immediate Shutdown Overview
NTC 0x0AA.0

FDD: SF049A

Description:

Loss of Assist Manager(LoaMgr) tries to avoid system shutdown when safe sensor redundancy is still in tact. However, in the event that conditions do not allow continued operation, it is LoaMgr’s responsibility to request system shutdown.

Diagnostic Overview:

LoaMgr includes many calibrations used to determine correct system response. Some of them can be given values to intentionally trigger this fault. LoaMgr reacts instantly because all debounce operations are assumed to happen in outside functions that feed inputs to LoaMgr.

Typical Fault Response:  

1. • –LOA Based Systems 

1. • • •Response for this diagnostic is F1.
        

Probable Sources (Most to Least Probable):

1. • –One of LoaMgr’s “Independent Signals” inputs has a runtime value that matches up with one of the “Response” calibrations whose cal value is set to 5. 

   • –One of LoaMgr’s “Independent Signals” inputs is receiving an initial value has a value that matches up with one of the “Response” calibrations whose cal value is set to 5. 

   • –Two or more issues exist in the system simultaneously, which automatically promotes LoaMgr response from calibrated values to a hardcoded response of 5 (Rapid Shutdown Requested).  Example:  System was already using TLOA due to lost handwheel torque signals, and then the system loses motor current signals.  Each response (HwTq and MotCurr) by itself might be cal’d to engage software-based mitigation (TLOA and Voltage Mode), but together they are deemed an illegal combination.  Illegal combinations result in F1 shutdown.