Toyota and Subaru are currently working hard to fix the issues that hound their jointly developed sporty coupes. The initial batches of Subaru BRZ coupe and its Scion FR-S twin, which is also known as Toyota FT-86 outside the US, have shown some problems caused by a software mapping glitch. While Toyota and Subaru officials say the problem is simply a software glitch and does not involve any mechanical defect, some coupe owners beg to disagree, saying that the fix that the carmakers have suggested has failed to keep the problem from recurring. According to Toyota spokesman Brian Lyons, when the vehicles’ engine control unit (ECU) is installed, it adapts to the powertrain and owner's driving patterns in a process called adaptive learning. However those settings are basically frozen in the ECU within 100 miles.
As for the coupes, some of the software coding that enables the ECU to set a "handshake" with the engine is in error. The ECU monitors particular driving conditions, and when the engine is deemed as out of tolerance, the software picks up an anomaly. When this occurs, the ECU lets out a fault code. When the ECU attempts to find an optimal driving condition outside its prescribed tolerances, it results to a rough idle or stalling situation.
Normally though, the check engine light illuminates, and a fault code of P0019 shows up on diagnostic readers. Toyota has suggested two ways to fix the problem. One is if the car has travelled less than 100 miles, a technician will reflash the ECU with the correct software mapping. The other is if the car has more than 100 miles, the mechanic would replace the ECU.