So I've had both of these error codes the last two weeks on a 2000 XJ Sport. I replaced both the camshaft and crankshaft sensors - camshaft is OEM, crankshaft is NAPA. The car starts, idles, and runs just fine though I will get an occasional backfire when picking up speed. My only guess is the circus, but I didn't notice any fraying on them. Given that it runs fine I'm just at a loss. Could it be an alignment issue?