P0355 and P0442

Nigel · Post by **Nigel** » 22 Jul 2020, 08:51

2001 c70 cabriolet

So I was driving normally and then these two codes came on. P0355 refers to the second igniton coil and P0442 refers to the air fuel.
How might these be connected, as they came on at the same time?

I had a P0304 cylinder 4 misfire which I fixed two months ago, at which time I replaced all the sparks and coil packs just to be safe. (I had narrowed the issue to coil pack #4).

I have had P0442 in the past and fixed it by tightening the gas cap but that did not work in this situation. Any thoughts?

Post by **scot850** » 22 Jul 2020, 09:21

P0442 is a minor evap leak in the emissions system. The fuel cap seal starts to split with age allowing air to leak by when the system runs a vacuum test for leaks in the system. That is not the only place the leak can occur. It can be in any of the evap system rubber hoses. That can include the 'J' hose near the carbon canister starting to fail or any other hose.

Misfires are a pain. It could be a bad coil or it may have a bad ground. Remove the park plug cover and check the coil. When you replaced the coils did you replace the rubber boot as well? Check for splits in the boot. The bolt holding the coil in place is the ground as is the point where it bolts to so clean the area.

You can see if the coil is bad by swapping with one from another cylinder and see if the issue moves. I replaced my coils with Volvo branded ones and one was bad out the box. You could also try one of the old ones if you kept the good ones.

Neil.

Nigel · Post by **Nigel** » 22 Jul 2020, 19:06

Hi Neil. Thanks for your reply.

I cleared the codes and switched the coil pack, at which point neither of the codes returned. This led me to believe there may have been a random short circuit caused by the motion of the ignition wires. Under the plastic cover the original plastic wire protectors were badly worn so I re-insulated the wires and installed new plastic protectors. I found one wire to a coil pack that looked as though it had been crushed with some exposed metal showing, this may have been responsible for the one time freak short circuit (I was driving in a bumpy area today and it is quite hot here). The car starts normally now, when both codes were showing it started quite roughly. This still leaves the question of the P0442 code, although it could also potentially be attributed to the suspected short circuit near the coil pack. I will update this post if anything else transpires.