[HELP] Throwing parts at a Check Engine Light (P0420, P0102)

Greetings, this is my first post. Thanks in advance for any insight.

I have a 2014 2.7L 2wd that originally threw P0420 indicating "bank 1 was operating below normal efficiency" last year. I brought it to a highly recommended independent shop. They replaced one of the catalytic converters (the cheaper one) and the code went away...For a month. I returned and they decided to replace the MAF sensor (after I took it off and cleaned it myself to no avail). The CEL remained on, but no driveability concerns arose. This was last year and I decided to just live with the CEL for a bit. I didn't drive it very often at the time.

Fast forward to a month ago and it starts stalling at idle. Then stalling while driving. The RPM dips to 500 and it dies unless I apply a lot of throttle to keep it alive. I replaced the spark plugs, no luck. I bring it back to the same shop and throw another $600 at it for them to diagnose it as a crank positioning sensor and replace that alongside the adjacent pigtail. The CEL goes away for 24hrs, then it comes back on and goes back to dying every other time I drive it.

I return a third time to the shop today and after an hour of free diagnostics they determine the windshield is leaking water onto my PCM and this is causing the issue. They tell me to take the vehicle to safelite for a repair or replacement. They claim the PCM doesn't look too bad and the issue should go away if I can prevent further water from dripping onto the PCM.

I pick up the truck after hours tonight and on the 8-minute drive home the CEL comes back on and the truck dies at a stop light. I took it to Advance expecting the same old P0420 code but now it's throwing P0102, "Mass Air Flow Circuit Low Input."

- Has any one had a similar issue?

- Does the water trickling onto the PCM description make sense?

- Would a dealership have better insight or should I stick with this independent shop?

Other notes: Battery is under a year old. It dies regardless of engine temps or run times. If I park it and leave it at idle it will die eventually 7 times out of 10. I've enjoyed 8 years of trouble-free ownership, just doing routine maintenance myself. Truck is bone stock other than wheels, tires, and a slight lift.

 

Welcome to Tacoma World. Sounds like a strange issue, I'm sure that is frustrating. I can't say anything about the PCM water leaking scenario because it's possible but I'm just some dude on the internet a thousand miles away so no way to know. Hopefully your PCM itself is OK, can't imagine that would be inexpensive.

Did some searching of old threads and there are many of them with those trouble codes. Best way to search is often going to Google and typing something like "site:tacomaworld P0420". You will find lots of information to help with possible fixes.

One in particular seems like a long-shot but worth mentioning - https://www.tacomaworld.com/threads/p0430-and-p0102-codes.495893/ . Says they fixed it by replacing the Y pipe gasket.

Good luck on getting it fixed.