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Symptom: P1594-CHARGING SYSTEM VOLTAGE TOO HIGH When Monitored and Set Condition: P1594-CHARGING SYSTEM VOLTAGE TOO HIGH When Monitored: With the ignition key on and the engine speed greater than 0 RPM. Set Condition: When the PCM regulates the generator field and there are no detected field problems, but the voltage output does not decrease. POSSIBLE CAUSES AMBIENT/BATT TEMPERATURE SENSOR GENERATOR FIELD DRIVER CIRCUIT SHORTED TO GROUND GENERATOR FIELD SHORTED TO GROUND AMBIENT/BATT TEMPERATURE SENSOR POWERTRAIN CONTROL MODULE (BATTERY VOLTAGE) POWERTRAIN CONTROL MODULE (GENERATOR RESISTANCE) TEST ACTION APPLICABILITY 1 Ignition on, engine not running. t, actuate the Generator Field Driver. With a 12-volt test light, backprobe the Generator Field Driver Circuit in back of All Yes → No → 2 Ignition on, engine not running. t, actuate the Generator Field Driver. With DRBIII t, stop the Generator Field Driver actuation. With DRBIII t, read the Target Charging voltage. Is the Target Charging voltage above 0 volts? All Yes → No → 3 Start the engine. t, read both the Battery voltage and the Target Charging voltage. Compare the 9Target Voltage9 to the 9Battery Voltage9 reading. Monitor voltage for 5 minutes, if necessary. Look for a 1.0 volt difference or more. All Yes → Replace and program the Powertrain Control Module in accor- No → Test Complete. 24 CHARGING |