Ford/Mercury hybrid stalling

July 15, 2013

Some 2005-2012 Ford Escape, Mariner Hybrid, 2010-2012 Fusion, Milan and MKZ Hybrid vehicles may exhibit a concern where the engine stalls soon after starting. This may actually be a crank/no-start condition being misdiagnosed due to the unique design characteristics of the hybrid powertrain system. DTC P0A7D (battery pack state of charge low) and/or P1A0C (engine disabled) may be present.

Conventional gasoline engines use an externally mounted starter motor which can easily be heard when starting the engine.

The hybrid powertrain has no external starter motor, and instead utilizes the motor/generator contained within the eCVT transaxle for this function. The motor/generator is almost silent in operation.

This higher rotational speed, along with the lack of audible starter motor noise may be mistaken for the engine actually having been successfully started after starting, then stalling. A conventional externally mounted starter motor rotates the engine at 200 to 250 rpm when starting the engine. The hybrid eCVT motor/generatot rotates the engine at 900 to 1,200 rpm for up to 30 seconds when starting.

If the perceived stall occurs with a cold engine within 30 seconds or less after starting is initiated, the engine is most likely in a crank/no-start mode and is not a start/stall.

Inadvertently following the Powertrain Control/Emissions Diagnostic (PC/ED) Manual, Section 3 symptom chart for a stall/quit at idle instead of a no-start/normal crank may eventually discharge the high voltage traction battery, resulting in DTC P0A7D and/or P1A0C. This may lead to the possible replacement of the high voltage traction battery