On November 30, 2009, the Office of Defects Investigation (ODI) opened a preliminary evaluation (PE09-054) to investigate alleged engine stalling, while driving in model year (MY) 2006 Toyota Corolla and Corolla Matrix vehicles.In its response to ODI's information request submitted on March 2, 2010, Toyota indicated that it had identified two possible causes of production defects of the engine control units (ECU) used in the MY 2005 through 2007 Corolla and Matrix vehicles equipped with the 1ZZ-FE engine.Failure mode A1 - BGA ball failure caused by improperly cured conformal coating applied to ECU circuit boards. This can cause cracks to form in the soldered joints of some components. Failure mode A2 - Varistor over heating; a glass coating is created on the surface of the Varistor during its production process.In case of an insufficient coating, a crack can occur in the surface of the glass coating. When ions are charged in the plating electrolytes after the glass coating process, the plating electrolytes can penetrate into the Varistor through the glass crack then an electrical short occurs. With respect to these failures, if the condition arises, it can potentially lead to one or more of the following: MIL on, engine stall or engine no start, harsh shifting.Of the approximately 155,000 warranty and extended warranty claims Toyota has analyzedthe projected 5 year failure rate of the ECU associated with an engine stall is 0.8%. This investigation has been upgraded to an Engineering Analysis (EA10-006) to further assess the scope, frequency and safety risks associated with the identified defects.
