Toyota and Subaru Offer Conflicting Software Fix Advice

An intriguing Auto Week story last week caught my attention involving a software problem in the new "GT-86" sports coupe that Toyota and Subaru jointly developed. According to the story, owners of the new 2013 Toyota Scion FR-S and its twin the Subaru BRZ have been complaining about rough idling and stalling conditions affecting their new cars. Both Toyota and Subaru say that the problems are not related to a mechanical defect but instead are related to a software “bug” related to the engine control unit (ECU).

Auto Week reports that a Toyota spokesperson told them that “when the engine control unit ... is installed, it adapts to the car's powertrain and owner's driving patterns, a process known as adaptive learning. Within 160 kilometers, those settings are basically frozen in the ECU.”

The spokesperson went on to state that the software that “allows the ECU to establish a ‘handshake’ with the engine is in error. The ECU monitors certain driving conditions, and when the engine is found to be out of tolerance, the software picks up an anomaly. When this happens, the ECU triggers a fault code. As the ECU tries to find an optimal driving condition outside its prescribed tolerances, a rough idle or stalling situation ensues. Typically, the check engine light illuminates and a fault code of P0019 shows up on diagnostic readers.”

Okay, sounds like incomplete ECU requirements definition and faulty testing scenarios may be the problem here, which, given that it is a new model sports car, is not entirely surprising.

What is a bit strange is the next part of the story. According to Auto Week, Toyota is saying that if the Scion FR-S has less than 160 km on it, it’s recommendation is that a technician reflash the ECU with new software. However, if the car’s mileage is more than 160 km, Toyota recommends the ECU be replaced.

However, Auto Week reports that Sabaru told it that the issue is “not a mileage dependent issue,” and that all that needs to be done is for the ECU to be reflashed, not replaced.

They are identical car engine electronics, aren't they?

And isn't 160 km of driving a rather small sample set for a sports car? I know whenever I bought a sports car, the first 160 km wasn't anything like the next 160.

Auto Week goes on to report that many owners of the new sports coupe have already had their ECUs reflashed or replaced, yet the rough idle and stalling conditions have not gone away: only now new fault codes apparently show up.

Makes you wonder which company is responsible for the ECU software, and whether there are other software bugs lurking about in the ECU code that testing haven't found. I’ll let you know whether anything new turns up.

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