Some 2017-2021 Ford GT vehicles may exhibit diagnostic trouble code (DTC) P166B present in the gear shift module (GSM) after an on-demand self test is performed. This is likely due to the driver door not being fully closed and locked during the on-demand self-test. A false P166B DTC can set if the driver door is not fully closed or if it is unlocked during the self-test. If P166B is still present with the driver door fully closed and locked during the on-demand self-test, continue with normal diagnostics in Workshop Manual (WSM), Section 307-05.
