[SOLVED] intermittent P0606

Year/Make/Model: 2013 Mazdaspeed 3
Mileage: ~79000
Location: St. Louis, MO
DTC's: P0606
Modifications: Cobb intake, Cobb turbo inlet, Cobb HPFP, CP-E intercooler
ECU/Tuning Software: Cobb Accessport V3
Tuner: Stage 1+
Is the concern intermittent? Yes
Can you duplicate the concern? Yes
Recent Repairs: Replaced battery and cleared

Went on a trip about 6 months ago and when I came back the battery was dead. I have noticed a slow start in the cold, so I replaced the battery. Fast forward a month my car was parked in my driveway, it rained the day before, slow start and A LOT of engine codes, but running ok. Thinking it's a short or grounding issue. Cleared the codes with accessport. During another rain, neighbor notices my headlights are on in the driveway. Try to turn off headlights without any ability to do so. Started the car and was extremely rough. RPM limited to ~1800 and no power, mutiple codes return. Took it to the shop and they cleared out debris from in and around the cowling, reset codes and appears to work after a day (dried out). Fast forward to two days ago. Rained again, hard to start, no power, only P0606 code. New symptom noticed- the rear hatch won't open when the rough idle/ no power. All other doors work buttons work. A day goes by and dries everything out. Jump the car since the headlights would not turn off again, cleared the codes again and car drove normal... rear truck button work again.

I THINK there is a water leak somewhere in the back (nothing is visible) of the car causing a short. I don't think the ECU is the issue even though I am getting a P0606 code. Any recommendations on connections or items that are likely to leak towards the back?

 

Update. I have noticed a faint ticking noise close to the ECU when the engine is off and cold. I am currently trying to locate it, but appears to be buried in a mess of wires. In the meantime I have flashed ecu back to stock to see if that was causing any issues. No change.

 

unplug and plug back in everything you can find in the area. some people have had the ECU connections loosen over the years and weird issues have been resolved by simply reseating the connectors

 

Unplugged battery then reseated the ECU connections, and relays in the fuse box. Many of the relays were stuck in pretty good. The EGI main was especially tough and appears to have a discoloration on one of the pins. I am currently ordering a replacement one. If I didn't know any better the ticking noise is coming from the ECU itself. The engine running has not changed... I feel this is the beginning of a rabbit hole.

 

Another update. Decided to undo, clean all the grounds I could easily reach. One by the battery, one near the intercooler, and two that I was able to access from under the car, near the throttle body? So far so good, but the real test will come when it's wet out.

 

Did any look particularly nasty?

 

Tentative solved! Want to test after a long soaking rain before I feel it's 100%. The small ground wire to the right of the intercooler (I believe for the hpfp) was particularly grungy. Sanded the surfaces clean, and put dielectric grease over the connection as a precaution.

 

ah that pesky ground good catch

 

SOLVED. I have had 3+ rain events and the car is working great. Will add my ECU tune back and finally enjoy my car again.