Mysterious CEL, misfire codes, all sorts of other codes ..

[jaybart]

Here's a mystery to ponder. Today my wife drove the '06 997S Cab in the rain. After a couple of miles the CEL started blinking, the engine started running with much hesitation (going downhill at about 35 mph). Then CEL went on solid. She called me, we swapped cars and I drove the 997 home. Can't say that it felt much different.

 

I read the codes - see attached images - with the durametric. There's:

• P0300: misfiring checksum error
• P0301: misfiring cylinder 1
• P0302: misfiring cylinder 2
• P0306: misfiring cylinder 6

• P0300: misfiring checksum error
• P0302: misfiring cylinder 2
• 8035: left seat heater
• C152: communication PSM control unit (drive)
• 8014: POSIP LIN no communication
• 8004: Terminal 50
• C131: Communication gateway control unit (CAN comfort)
• 8007: Gateway incorrect coding
• C122: Communication driver's door control unit (comfort)
• C123: Communication passenger's door control unit (comfort)
• 8042: Front luggage compartment unlocking
• 8029: Right fog light
• 8009: Door h. button, inner sh. stroke
• C102: CAN single wire operation "comfort"
• 8007: No load on left subwoofer

So, after capturing the screen shots I erased all codes and took her for a test drive. No issues on the drive. The only codes after the drive were:

• 8007: Gateway incorrect coding
• 8009: Door h. button, inner sh. stroke
• 8007: No load on left subwoofer

Those all seem benign and explained - except the subwoofer but that's not a high priority to troubleshoot.

 

So, what do you think? What may have cause this? Spark plugs are 4 1/2 years old (24,000 miles) and I was going to replace them end of this month as a matter of routine. Besides the Denison BT GW and a Smarttop module everything else is stock (PSE, PASM, leather interior, power memory seats, steering wheel with controls, navigation, CD changer, Sport Chrono, dimming mirrors).

 

My theory? Either

• some connector got wet causing all this, or
• the revs dropped due to misfire from bad fuel in stop and go traffic causing voltage fluctuation leading to all sorts of faults registering.

Looking forward to your thoughts and direction.

[wizard]

You might want to check your coil packs when changing your plugs - sooner rather than later.

[Ahsai]

^This. Just replace the coils if they are original.

[dammad]

Perhaps your cab drains are blocked at water is getting to the electronics under the drivers seat? Check for water under the carpet in the rear foot wells.

[dammad]

Perhaps your cab drains are blocked at water is getting to the electronics under the drivers seat? Check for water under the carpet in the rear foot wells.

[jl-c]

Good luck with this, I think the 

• 8007: No load on left subwoofer   is caused by the Dension because I always get this too!  It is good advice to replace plugs and coils, I did mine when I got the car so I had a starting point to work from. Also did oil change filter,coolant, stat, air filter and belt.

[dphatch]

As others have already mentioned, I vote for coils being worn out given the age of the car.  If you can jack up the back of the car and remove the rear wheels it is possible to get a good at the coil packs with a good light source and a mechanics mirror. You're looking for cracks in plastic casing and/or clear epoxy sealant on the face of the coil used to weather proof it.  Once  moisture is able to enter the coil pack they are toast. 

[jaybart]

Thanks for all input. I replaced spark plugs and coils. When I did I found that the coil on the left middle cylinder was loose - both screws were missing. I guess that would explain the misfire ....

[Ahsai]

Glad you got it sorted and thanks for closing this.