2000 S80 CEL Flashing after Coil Change

admiral · Post by **admiral** » 15 Jan 2015, 19:05

The CEL started to flash, and the car had a rough idle. I pulled the codes and got P0303. To diagnose the problem, I switched the coils for the 1st and 3rd cylinder and cleared the codes. Drove it down the street, CEL flashed again. The code was now P0301. (P0303 was gone.)

I thought I was pretty clever, so I replaced the bad coil. I wasn't that clever. CEL still flashes. Thinking I somehow bought a bad coil, I swapped the 1st and 3rd coils again, cleared the codes, and drove. CEL still flashed and still pulled P0301. I changed the spark plugs. No difference.

So the problem's moved from the 3rd to the 1st cylinder. Probably because I'm an idiot. What could I have screwed up? Thanks

MyS40T4 · Post by **MyS40T4** » 15 Jan 2015, 19:58

Hi,

There's a ground lead from the ignition coil wiring loom that must be grounded (held by a M6 bolt to the head) that will result in a misfire if not attached... It's roughly around the 2nd/3rd coil in from the gearbox end of the engine from memory...

admiral · Post by **admiral** » 16 Jan 2015, 07:16

Thanks. It looks like I unfastened that bolt at some point in the process.

MyS40T4 · Post by **MyS40T4** » 16 Jan 2015, 16:25

No worries - caught me too!