Suddenly, ALL the codes...

[SeanPwnery]

So recently in my part of Texas, we've been getting quite a bit of rain - not Kerrville levels, but pretty steady, heavy occasional rain several times a day - a lot of the roads in Houston get high water pretty easily. About 5 days ago or so I was stuck in the right lane because NOBODY wanted to let me in, so I had to blast through a few water puddles that were 1/2 to 3/4 of a lane wide doing about 30mph or so. Everything seemed okay, I got past the high water areas, drove another 5 or 6 miles, and within a block from my house, the dash started screaming at me to "Service Electronic Throttle control" - a message I've seen before - however, rather than a steady icon, it was blinking. Next, I noticed the transmission was locked in 4th gear - limp mode. Trying to accelerate from a dead stop in 4th - pretty painful. Made it home, hooked up my Autel, and this is the code list :
P0651
P26a7
P2681
P2122
P00F5
P0006D
P2138
P26AB

The only TCU code was the limp mode one, I wanna say it was U1428 or something to that effect.

So the P26a codes are the 3-way coolant valve, I know this because I had this error literally 8 months ago, changed the valve and life was good - but it came RIGHT back after only 8 months - note to self, buy the Mopar valve this time. I believe a lot of the errors are a "cascading effect" where one kicks off, then others downstream fall like dominos. Either way, I left the truck at home for 3 days hoping things would dry out over time, then coming home from work, resetting the ECU, and trying to drive around the block. The first day I made it 4 miles, then had to limp it home, pulling over, resettings codes, firing it back up, driving about a mile or so, and repeat til I got home. This time I completely disconnected the battery and left it overnight. The next day tried it again, but only up my street, 1 block circle, and it didn't even make that without going bonkers, though limp mode was 3rd gear only. This happened yesterday as well - day 3.

So I went over to the neighbor's place, the diesel and heavy equipment mechanic that got me running a year or so prior for those that remember that dealership debacle. Without saying what I planned to do, I explained the 3 days leading to where I'm at now, and he came up with the same thought process I did - disconnect all the connectors under the hood one at a time, spray it all with contact cleaner, apply dielectric grease and try again. I did that this morning focusing on the passenger side of the engine since that's where the puddles were the most prominent. I managed to do I believe all of them, including the ECU, glow relay connectors, various sensors, right up to the mid-line of the engine where the MAP and I assume Air temp sensors were. Anyway, fired it up just before today's monsoons began and aside from a little burp trying to start (I shot a bit of cleaner down the EGR tube and cleaned the MAP), it fired up and idled fine.

Felt pretty good til I took it around the block... pooched halfway around, went home in defeat. This time the only code that popped up is P0651 - voltage fault in the 5v reference circuit - side B. I'm beginning to think coincidence may have come calling, and the water may have had nothing to do with it, but I thought I'd pose that possibility around here first. Side B includes the throttle pedal sensor (so the pedal assembly). Again, with the one code, it went to "Service electronic throttle control" on the dash, and locked the transmission in 3rd only. The one oddity this time was if I took my foot off the brake, it would idle up to 3,000rpm - but if I pressed the brake pedal, it would drop to about 800rpm. That one's got me stumped.

One last tidbit which may ring a bell with some of you - my ignition cylinder, where the keyfob fits in, had started saying "Wrong Key Fob" about a week prior to the above issues. Not sure if they're related, but I noticed if I jiggled the fob a little before turning it, I had no issues starting or messages. Swapping the coincell battery didn't solve that one.

 

[SeanPwnery]

Correction... U1424

 

[SeanPwnery]

For once, a happy-ending update.

So in my paranoia and constant defcon-1 levels of worry since most dealerships in my area are criminal when it comes to estimates, and how they seemingly ensure my third-party warranty people deny ANY coverage for the 3 years I wasted on that service, I started to think backwards from the beginning. Just to drive home the point, I called the dealer Friday explaining everything that happened thus far, and their quote was nearly $9k because - like the last time with my fuel system, they wanted to replace everything connected to that side of the "Circuit B" system including the ECU. F**king crooks.

What ended up causing the entire 5v reference circuit to go crazy was ... the 3-way heater valve - which I had literally replaced 11 months ago.

Yep. That one sensor on the valve was in such a bad way, that everything downstream of the circuit would fail to receive signal which included the TPS on the accelerator, the variable vane control on the turbo itself, the DEF injection system somehow, the MAP Sensor, and the air-intake temperature sensor AND throw the transmission into limp mode.

All solved. Seeing as how I changed this valve before, the 2nd time around went surprisingly fast - about an hour and a half - some of that just waiting for coolant to drain. Been running so far for 45 minutes or so, along with a drive to the car wash, and I'm semi-confident I've got it licked.

So... for future reference, if your rig goes bonkers with the above codes - start with the first code thrown after the ECU reset - my P26a7 code lit up immediately after the clear which led to the valve. Everything that follows that one could simply be downstream signal failures.

 

[1shadowsabre]

Congratulations! Glad you got a win on this one!