The ongoing problem with code P0017, exhaust cam sensor, has been difficult to solve. I cleaned sensor terminals, spread pins in the sensor to force tighter contact fit in the receptacle. All of these did not fix the problem as the code would reappear. The longest interval before code appearance was about 10 days.
Finally on Thursday evening, May 20, I decided to exchange the exhaust cam sensor with the intake cam sensor and clear code P0017 from the engine controller memory. No diagnostic code appeared for the intake sensor so I reasoned that if I swapped the sensors and the diagnostic code appeared on the intake side that would mean the sensor was defective. If code P0017 still appeared on the exhaust side that would indicate the sensor was good and the problem lies with the wiring.
Vehicle has been driven about 600 miles since May 20. Code P0017 and P0016 (exhaust and intake cam sensor) have not appeared. I am not complaining but it definitely seems odd that switching 2 sensors prevents a diagnostic fault code from appearing.
Of interest is the fact that the emission label underneath the hood indicates California emissions though the car was placed in rental fleet service in Texas. California emissions requirements are more stringent that the rest of the USA so that may be a factor in this discussion. Now the new problem. In scanning for any codes I am now getting pending code P0420, catalyst efficiency. I received that in early April and a dealership service department applied the software controller upgrade outlined in TSB # 18-018-07A. That eliminated code P0420. Now it is reappearing as a pending code but the check engine lamp has NOT illuminated. I used a scan tool to view the real time behavior of the upstream and downstream oxygen sensors. At 750 engine rpm and the engine at 212 deg F operating temperature, the upstream sensor switches between voltages .08, .10, .20, … , .70, .80, .90. So it appears to be functioning properly as it is switching smoothly between rich and lean conditions in the exhaust gas. The downstream sensor voltage readings at 750 rpm are .68 , .70, .71 . Are these voltages proper for the downstream sensor or should they be closer to .45?
From my research on the internet the downstream sensor should stay close to its midpoint value of .45 which would indicate neither rich nor lean. I believe the pending code P0420 is being set by the controller software because the voltage readings between the upstream and downstream sensors are too close to each other. Has the catalytic converter failed prematurely or is it possible that the downstream oxygen sensor is defective? I would think that if the downstream oxygen sensor failed it would set its own unique code. Any thoughts about this???
Edited by AllanC, May 25, 2010 at 08:39 pm.