LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Ford >> 1991 >> Probe LX, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests - 3.0L >> TFI-IV System >> CCD Systems >> Key On Engine Off (KOEO)
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Key On Engine Off (KOEO)

3)  Turn ignition off and remove test pin. Reconnect wire to "S" terminal on relay. If approximately 90% of Battery Voltage (VBAT) is not present at these terminals, repair open circuits in wiring harness as necessary. Check ignition switch for faults. See appropriate wiring diagram. If voltage was as specified, reconnect module and go to next step.

4)  Attach a 12-volt test light between ground and coil negative (-)/tach terminal No. 2 at TFI module. Turn ignition on and crank engine. If test light flashes brightly during cranking, go to PIP Sensor/Stator Test. If test light stays on during cranking, check for open in coil negative circuit between coil and TFI module connector. Repair circuit as necessary. If no open circuits are found, ignition module is shorted internally, replace TFI module and retest.

5)  If test light is always dim or off during cranking, check voltage to coil positive (+) terminal. If voltage is not present with key on or during cranking, repair open in primary circuit between battery and coil positive (+). If light flashes intermittently, check ignition module resistance. If voltage is available at coil, go to COIL TEST and check ignition coil.