Originally Posted By: kingrob
My biggest gripe about the OBD II system is that it will pick up all the useless trivial sensor output that will hinder you from passing inspection, but it won't register with most important things like bad spark plugs, wires, 02 sensors, catalytic converters, intake leaks, bad vent hoses, etc. Maybe my exerience is atypical but I had a sparkplug with the electrode completely rotted off making the engine miss, no CEL. Intake gasket leak, no CEL. Plugged up Cat, hole in the exhaust, no CEL. Bad 02 sensor, yep, no light. The only things it does seem to pick up are things like map sensors, crank pulley sensors and other things I don't care about.
Interestingly enough, the CEL did come on in my 07 Malibu when the intake was leaking. It was leaking oil and some oil getting into the combustion chamber caused some odd firing. It triggered the light for a little bit, but it went off. We checked it out, and sure enough nothing odd was going on with the fuel or ignition and the code was generic. We looked at the back part of the engine that I couldn't easily see and found the oil seeping out.
My biggest gripe about the OBD II system is that it will pick up all the useless trivial sensor output that will hinder you from passing inspection, but it won't register with most important things like bad spark plugs, wires, 02 sensors, catalytic converters, intake leaks, bad vent hoses, etc. Maybe my exerience is atypical but I had a sparkplug with the electrode completely rotted off making the engine miss, no CEL. Intake gasket leak, no CEL. Plugged up Cat, hole in the exhaust, no CEL. Bad 02 sensor, yep, no light. The only things it does seem to pick up are things like map sensors, crank pulley sensors and other things I don't care about.
Interestingly enough, the CEL did come on in my 07 Malibu when the intake was leaking. It was leaking oil and some oil getting into the combustion chamber caused some odd firing. It triggered the light for a little bit, but it went off. We checked it out, and sure enough nothing odd was going on with the fuel or ignition and the code was generic. We looked at the back part of the engine that I couldn't easily see and found the oil seeping out.
