Upstream Oxygen Sensors Slow Response - P0133, P0153

Upstream Oxygen sensors slow response - P0133, P0153
The failure criteria for this monitor is the measurement of the time taken for the upstream sensor to attain a calibrated AFR reading following fuel re-instatement after an overrun fuel-cut. The slow response monitor measures the response time of the sensor to react when the AFR changes from a known lean state to a known non-lean state. The monitor operates after fuelling has been reinstated and the EMS is in idle speed control mode, following a period of fuel cut-off (ORFC). If all execution conditions are satisfied the monitor increments a response timer, if the timer exceeds a failure threshold prior to the sensor current switching back to a non-lean condition (6.97 ma) a failure end judgement flag is set. If the current signal passes through the lean limit prior to the timer exceeding the failure threshold, then a normal end judgement is set. It should be noted that the slow response monitor is a single shot monitor, which only executes once per drive cycle. Fuel cut operation - a timer is employed to ensure that a minimum period of fuel cut off is achieved prior to executing the monitor, thus allowing the sensors to respond to the lean AFR fuelling shift, which occurs during the period of fuel cut off.