Weak Spark on 1 Cylinder

br1gold · Post by **br1gold** » 18 Sep 2016, 20:44

I have an 2002 S60 AWD with a weak spark on the number 3 cylinder. I have swapped the plug, coil, injector with other cylinders, just to satisfy curiosity. I am throwing code P-0303. This miss has been occurring once in a blue moon for at least 1 1/2 years and could not find any cause. It has finally broke and I am needing a good starting point. I have been looking at the Ignition Control Unit but can not find its location on the car.

fixer333 · Post by **fixer333** » 20 Sep 2016, 00:47

How is the compression on that cylinder?

Post by **abscate** » 22 Sep 2016, 13:08

The coil on plug ignition works with constant 12 VDC on the coil and the ECU grounding the coil to fire it.
Once you confirm the 12V is good, and the wires are good, swapped coils and plugs, the only thing left is the grounding wire to the ECU.

br1gold · Post by **br1gold** » 24 Sep 2016, 11:52

Where is the ground wire for the ECU located? I am only having an issue on 1 cylinder.

br1gold · Post by **br1gold** » 04 Oct 2016, 20:19

After an exhausting troubleshooting, it IS my ECU!