Originally Posted By: ram_man
So the dealer... replaced the oil pressure sending unit. But didnt clear the code. Well I noticed in their parking lot. I told them immediately , they said the guy that did the job was gone for the day but if I wanted to wait 20 minutes they would have someone do it. Well I didn't have time. I said I would delete it myself. So when I came home I plugged the scanner in and erased the code. Well after that I cycled the key three times amd the odometer said done so the code was gone. Well it came back pretty quick. And when I plugged the scanner back Into it it said there was no codes present. But cycling the key 3 times pulls up the p0522 code. What gives? Why does it say theres no codes when there obviously is....any ideas?
My understanding of OBDII and DTC's are that the code may be cleared (no CEL), but the code remains in another location in the ECU memory.
I think this is what your scanner is seeing. I think it's kind of a history log of sorts.
This "history" memory will clear itself after a set number of run cycles. IIRC, a typical run cycle consists of allowing the engine to reach operating temperature, shut down and allowed to get stone cold. Mileage might be in there as well. No amount of key on-off cycles will clear this memory. The ECU has to see run cycles.
I'm pretty sure that since the CEL came back on soon after you cleared it the first time, the problem isn't fixed.
With OBDII systems, I've always been told NOT to clear the code(s) to shut off the CEL. If the repair was effective, it would turn off itself.
This has been true with two DTC/CEL repairs I have done on my '03 GMC Safari. One was with an O2 sensor issue. The other was with a cylinder misfire issue. In both cases, I did not attempt to clear the DTC after I made the repairs; the CEL shut itself off and did not return.
