Diagnostic Aids
After confirming DTCs P1153, use scan tool to access CURRENT DATA to confirm voltage output of heated oxygen sensors (bank No. 2 sensor No. 1). ECM controls voltage of AF+ and AF- terminals at ECM to a fixed voltage (3.3 volts at AF+ terminal; 3.0 volts at AF- terminal). It is impossible to confirm A/F sensor output voltage without using a scan tool. OBD-II scan tools will display one fifth A/F sensor output voltage as Lexus scan tool will. Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.
During fuel enrichment, output voltage of A/F sensors maybe less than 0.56 volts (2.8 volts on Lexus scan tool). During fuel cut, output voltage of A/F sensors maybe more than 0.76 volt (3.8 volts on Lexus scan tool). If output voltage of A/F sensor remains at 0.66 volt (3.3 volts on Lexus scan tool) during all conditions, A/F sensor circuit may be open. If output voltage of A/F sensor remains at 0.76 volt (3.8 volts on Lexus scan tool) or more during all conditions, A/F sensor circuit may be shorted. If output voltage of A/F sensor remains at 0.56 volt (2.8 volts on Lexus scan tool) or less during all conditions, A/F sensor circuit may be shorted.
Thursday, May 31st, 2012 AT 4:42 PM