Q: Code P0705 - 2008 Ford F-150

As with most diagnostic trouble codes, code P0705 does not necessarily identify failed parts. All you can assume with the code is that the PCM is not getting the signal it "expects" from the switch - no signal at all or the PCM itself has failed (rare, last of the last to consider). The cause for no signal could be due to various reasons, including something as simple as a corroded, high resistance wire.

So with P0705, the only way to tell if the cause is the switch is to test it. Typically a technician will test the neutral start switch in the field based on the Factory Service Manual diagram of the switch. In each gear position, the mechanic simply looks for continuity across the specified terminals. If continuity exists on the right pair of terminals, for each possible gear selection, then the switch is fine.

Further diagnostics, would include testing for an open or short in the switch circuit back to the PCM as well as possible maladjustment of the shift linkage which itself could cause the switch internals to not be making the right contacts for the particular gear you have selected. If you would like to have this checked, a certified technician from YourMechanic can come to your car’s location to diagnose the Check Engine Light and follow through with proper repairs.