Hybrid Start/Stall Diagnosis

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Hybrid Start/Stall Diagnosis

Some 2005-2012 Ford Escape, Mercury Mariner Hybrid, 2010-2012 Ford Fusion, Mercury Milan and Mercury 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 then stalling. A conventional externally mounted starter motor rotates the engine at 200-250 rpm when starting the engine. The hybrid eCVT motor/generator rotates the engine at 900-1,200 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 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.

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