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Engine Codes

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New User

Dec 31, 2021, 4:24 PM

Post #1 of 2 (922 views)
Engine Codes Sign In

I have a 2016 Toyota Corolla LE in which a few codes have come on: U0101-Lost Comm with TCM, U0100-Lost Comm with ECM/PCM "A', PO456-EVAP Control System Leak Detected. When I reset the check engine light and ran the scan a second time, then the P0456 code did not appear but the other codes U0101 and U0100 still showed after the scan.

Any ideas what might be the causes of the mentioned codes and might need to be repaired if anything? I just replaced the air filter and cabin filter a day before any of the codes came on. I'm sure that this is just a coincidence but just throwing it out there. Thanks.

Hammer Time
Ultimate Carjunky / Moderator
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Dec 31, 2021, 4:48 PM

Post #2 of 2 (918 views)
Re: Engine Codes Sign In

The P0456 is a vapor leak in the tank system and you will need a smoke test to find that.

The "U" codes are communication codes. There is a communication network that connects all the modules together on the same bus line.

These could be due to a defective computer or related wiring. It's going to take a knowledgeable tech with the right equipment to diagnose that problem.


We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

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