Ground Circuits

WARNING: This page does not describe the selected car, but rather 26 other vehicles, including the 1999 Mercury Tracer, 1999 Mercury Sable, 1999 Mercury Mystique, 1999 Mercury Mountaineer, and 1999 Mercury Grand Marquis. However, it is still accessible from the selected car via links, so may be relevant.

Turn ignition off. Locate PCM. See POWERTRAIN CONTROL MODULE LOCATION table. Using a DVOM, check continuity between ground and PCM connector pins. See IDENTIFYING PCM GROUND PINS. See Figure. If continuity does not exist, repair open ground circuit as necessary. If continuity exists, go to next step.

IDENTIFYING PCM GROUND PINS

Application			PCM Ground Pin No.
Continental, Crown Victoria, Grand Marquis & Town Car			3, 25, 51, 77 & 103
Contour, Cougar & Mystique			24, 51, 77 & 103
Econoline
4.2L & 4.6L			24, 25, 51, 76, 77 & 103
5.4L			3, 24, 25, 51, 77 & 103
6.8L			3, 23, 24, 25, 51, 76, 77 & 103
Expedition & Navigator			3, 25, 51, 77 & 103
Mustang			24, 25, 51, 76, 77 & 103
3.8L			24, 25, 51, 76, 77 & 103
4.6L 2-Valve			3, 25, 51, 77 & 103
4.6L 4-Valve			25, 51, 77 & 103
Pickup
F150 & F250
4.2L & 4.6L			24, 25, 51, 76, 77 & 103
5.4L			3, 25, 51, 77 & 103
Super-Duty Models			3, 23, 24, 51, 76, 77 & 103
Ranger			24, 25, 51, 76, 77 & 103
Sable & Taurus			24, 25, 51, 76, 77 & 103
Taurus SHO			3, 23, 24, 25, 51, 76, 77 & 103
Windstar
3.0L			24, 51, 76, 77 & 103
3.8L			24, 25, 51, 76, 77 & 103

Touch negative lead of voltmeter to a good ground. With vehicle running, backprobe positive lead of voltmeter to each ground terminal. Voltmeter should indicate less than one volt. If reading is greater than one volt, check for open, corrosion or loose connection on ground lead.