Test C: System Overcharges (More Than 15 Volts)

WARNING: This page is about a different car, the 2003 Mercury Sable, 2003 Ford Taurus, 2002 Mercury Sable, and 2002 Ford Taurus. However, it is still accessible from the selected car via links, so may be relevant.

Connect New Generation Star (NGS) tester to Data Link Connector (DLC). Turn ignition on. Using NGS tester, perform Powertrain Control Module (PCM) self-test. If no DTCs are retrieved, go to next step. If any Diagnostic Trouble Codes (DTC) are retrieved, perform appropriate test in accordance with DTC retrieved. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
Turn ignition off. Disconnect NGS tester. Start engine. With engine running and all accessories turned off, measure the voltage at battery while varying engine RPM. If the voltage is more than 15 volts, go to next step. If voltage is not more than 15 volts, go to step 4.
Turn ignition off. Disconnect generator 3-pin connector. Turn ignition on. Measure voltage between ground and generator harness connector terminal No. 3 (Orange/Yellow wire). See Figure. If voltage is less than 0.5 volt from battery voltage, go to next step. If voltage is 0.5 volt or more from battery voltage, repair Orange/Yellow wire. See WIRING DIAGRAMS . After repair, clear DTCs and test system for normal operation.
Turn ignition off. Connect generator 3-pin harness connector. Start engine. Check generator output. See GENERATOR LOAD TEST and GENERATOR NO-LOAD TEST under ON-VEHICLE TESTING. If generator is okay, system is operating correctly at this time. Check for corroded connections and check integrity of Orange/Yellow wire. If generator is not okay, install new generator. See GENERATOR under REMOVAL & INSTALLATION. Clear the DTCs. Test the system for normal operation.