Corolla Starts and Stalls – No PCM Communication
Jan. 03 2023
Jan. 03 2023

Vehicle: 2010 Toyota Corolla, L4-1.8L (2ZR-FE), Automatic Transmission/Transaxle

Mileage: 92,009

Problem: This vehicle was towed in because it wouldn’t stay running. It would start then stall after a couple seconds.

Case Details: The only diagnostic trouble code (DTC) present was U0100 - Lost Communication with the ECM.

The technician found this DTC in multiple modules, such as the ABS, Certification ECU and Combination Meter. He checked the fuses and found a blown EFI1 fuse. He replaced it and it did not blow with the key on. He got the engine to start, and the fuse blew again on the test drive.

According to an ALLDATA Tech-Assist consultant, that fuse supplies power to a handful of other components. Somewhere, a wire is rubbing through to ground or a fuse-controlled device is shorted.

The technician used the powertrain control wiring diagram and looked at all the devices protected by the EFI1 fuse. While inspecting the wiring circuits for each of those devices, he found the rear oxygen sensor wiring harness was touching the exhaust heat shield. Every so often, vibration would cause a wiring short to ground.

Confirmed Repair: He repaired the oxygen sensor wiring and rerouted the harness so it wouldn’t rub on anything. After the repairs, he cleared the DTC and went on a test drive. This time, no stalling issues. Problem fixed!

The ALLDATA Tech-Assist team fields cases like this every day. See how Tech-Assist can help your shop save time and money with on-call diagnostic support from ASE-certified Master Technicians. More Tech Tips 

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