Hey guys, my SEL illuminated a few weeks ago. Used my Peake tool to see what kind of codes were present and came up blank!? Have checked for vacuum leaks, none that I could find, albeit not the end all. I have new spark plugs, new coil packs, cleanded MAF, checked vacuum hoses for any possisble issues...ETC. I replaced the pre oxygen sensors about a year ago,threw a code, but I did not replace post sensors. They only had one in stock at the time, and so I replaced pre with intent to replace post at at later date. Have not read anywhere if doing so will throw SEL, without registering a code. I am aware that Peake does not have the capability to read ALL codes...Unfortunately, I have to smog for registration by mid month and if I can't get it fixed, the Stealership is my only option. Read the post about trouble shooting smog pump, check valve, et. al..will also give it a try and just maybe...Thanks in advance!