CVHE-SB-32A 82
Information on the Oil Pressure Sensor
Calibration Diagnostic
UCP2 uses two pressure sensors (one in the sump, one in the discharge) to detect oil flow.
When the oil pump has been off for at least 5 minutes, the sump and discharge pressures are
compared. If the absolute difference between the sensors is less that 3 psid, the difference is
zeroed. If the absolute difference is greater than 3 psid, a sensor calibration diagnostic is called
out.
Changes made to -11 Circuit Software (X-13650451-09 hardware) to improve Prevac
performance:
The 3 psid calibration check was modified to require 90 consecutive seconds of greater than
3 psid before a diagnostic is issued.
During Prestart, the calibration check is stopped when the evaporator flow is first sensed.
Previously the calibration calculation and diagnostic check were terminated when the oil
pump turned on. The change was implemented to avoid nuisance pressure fluctuations
caused by the start of evaporator water flow and the guide vanes bpi search.
Suspend calling out the oil pressure sensor calibration diagnostic until evaporator water has
been flowing for a minimum of 5 minutes.
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