2012 Tundra 5.7L stalling. Erratic Data. CALLING ALL PROS! SOLVED

As I said its a 2012 Tundra TRD 5.7L 4x4. The most obvious symptom is the stalling. Will start fine and idle for about 15 to 20 seconds the stall..slowly. After sitting outside the garage all weekend untouched it ran for about 15 min today. I have been testing wiring and sensors with guidance and data from Mitchell On Demand and an Autel MaxisysElite. Throttle motor passes. MAF passes. Coolant sensor is brand new and has an erratic value in the LiveData. It will bounce from negative values to 200+ quickly. Also while the engine is running the vehicle speed will go as high as 35 mph...in park (On the Autel Live Data). The APP triggered codes so I tested, the sensor passes except for at WOT the voltage would drop out. Unsure if related but the 4-LO light is flashing as well. We dont work on many toyota vehicles so your input is greatly appreciated!

 

Do you have a remote start on your truck? If you do, I would use the spare key keeping the remote start fob away from the truck and see if it will start and run. If you don't have a remote system then I would still try the spare key because it has a chip in it to start the truck. If it then you have a bad key and or a bad remote start fob. Have you checked your battery for condition? You can pull the battery and have it tested at most Auto Parts Stores. I have heard issues with a bad battery doing this start stall thing. Another thing I have heard is make sure the air intake tube is secure in place and has not fallen off. That also will cause the same problem.

 

any chewed harness wires by mices ? especially if the truck been sitting for some time.

 

I've seen the slow stall before, it usually follows a battery drain.... speedometer going to 35 is an oddity, since it shouldn't be moving in P or N. I would suggest get your battery tested, charged, or swap it out. If that doesn't resolve issues, start going through wiring on your transmission as it appears a short may be triggering the speedometer to move.

If the truck starts fine, I would suggest to sit in your truck and let it idle around 20-30 minutes and observe the idle and give it gas if it drops to 500rpm or appears to creep below, rev it to about 1k just to make sure it stays on... I've done this cycle a few times as sometimes my truck sits for a while as well and the battery dies...

 

Bad gas? Did you fill up right before it happened?

 

This isn’t my chart but maybe it’ll help.

Says just 4 low flashing in MAF backwards. Did you change the MAF sensor?

 

Thank you all for your input, disregard the live data..that was a software issue with my scanner. I'm not sure why the lights would have been flashing but the stalling/sometimes no start condition was solved with a dealer supplied fuel pump ecu.

 

Sweet, glad your problem is solved.

 

Wow, very useful chart! Is it complete? If not, can you post the rest of it or post a link?

 

I got it from another post on here, but don’t remember which one now. I saved the picture from the post.