Initial Inspection and Diagnostic Overview
MiscellaneousParameters and conditions to begin closed loop operation
General
To prevent damage of the HO2S caused by thermal shock it is necessary to delay the electrical driven heat up until the dew point of the water in the exhaust gas. Basically an exhaust gas temperature model is used to calculate the begin of closed loop operation using ECT, IAT and MAF.
Conditions for closed loop operation of the first control loop
To guaranty a proper Oxygen sensor heat-up the heater starts depending on engine temperature on a low level of heater power. Upon the exhaust temperature reaches a level where no liquid water is expected to be in the exhaust system (dew point exceeded) the heater power is controlled to achieve normal ceramic temperature of the Oxygen sensor. The ceramic temperature has to be > 610 °C for linear sensors. Specific temperatures are mentioned in the individual summary table.
Upon the integrated air mass after engine start exceeds a threshold, calculated at engine start based on engine start temperature and IAT, the due point is exceeded. In that case, the heater power will be increased until the sensor readiness is achieved and the sensor is considered to be ready for closed loop control.
The criteria for sensor readiness of the linear are:
- no fault from: LSU-Heater, LSU-Signals, LSU-IC
- LSU is heated up to a ceramic-temperature of > 610 °C.
Parameters evaluated to begin closed loop (first control loop)
The target is to begin closed loop operation in a very early state after engine start. However closed loop is delayed if engine is operated according the catalyst heat-up strategy. In the table below the importance parameters are listed.
Under cold start FTP75 conditions (around 20 °C) the concept reaches the closed loop condition within 20s to 30s.