DTC P1594: CHARGING SYSTEM VOLTAGE TOO HIGH Dodge Ram Wagon B1500

Note. For connector terminal identification, see CONNECTOR IDENTIFICATION . For circuit identification and wiring diagram, see RAM VAN & RAM WAGON wiring diagram in WIRING DIAGRAMS article.

Note. DTC P1594: CHARGING SYSTEM VOLTAGE TOO HIGH is monitored with engine running. DTC may be stored in Powertrain Control Module (PCM) when PCM senses attempts to regulate generator field indicate no field problems but voltage output does not decrease. Possible causes are: defective Battery Temperature Sensor (BTS), defective generator, defective PCM, defective connector or defective wiring.

1. Turn ignition on, with engine off. Using scan tool, actuate Generator (GEN) field driver circuit. Using a voltmeter, backprobe GEN field driver circuit (Dark Green/White wire) at back of generator. If voltage shifts from low to high, go to next step. If voltage does not shift from low to high, go to step 6).
2. Start engine and allow it to idle. Using scan tool, read TARGET CHARGING voltage. If voltage is more than zero, go to next step. If voltage is zero, go to step 4).
3. With engine running, manually set engine speed to 1600 RPM. Using scan tool, read TARGET CHARGING voltage and BATTERY VOLTAGE. Compare readings and monitor voltage for 5 minutes (if necessary). If voltage difference is more than one volt, replace PCM. Perform TEST VER-3A. If voltage difference is not more than one volt, test is complete.
4. Turn ignition on, with engine off. Using scan tool, read Battery Temperature Sensor BTS temperature. Using a thermometer, measure underhood temperature near battery tray. If BTS temperature is within 10 degrees of underhood temperature, go to next step. If BTS temperature is not within 10 degrees of underhood temperature, replace BTS. BTS is located under battery. Perform TEST VER-3A.
5. At this time, PCM is assumed to be defective. Replace PCM. Perform TEST VER-3A.
6. Turn ignition off. Disconnect GEN field terminals connector at back of generator. Clean and/or repair connector as necessary. Using an ohmmeter, check resistance across GEN field terminals. If resistance is less than 5 ohms, repair or replace shorted generator. Perform TEST VER-3A. If resistance is 5 ohms or more, go to next step.
7. Turn ignition off. Disconnect PCM connectors. PCM is located in engine compartment. See PCM LOCATION table under SYSTEM DIAGNOSTICS. Disconnect GEN field terminals connector at back of generator. (Схема №23) Disconnect battery. Clean and/or repair connectors as necessary. Using ohmmeter, check resistance between ground and PCM connector, GEN field driver circuit (Dark Green/White wire). If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair GEN field driver circuit for short to ground. Perform TEST VER-3A.
8. At this time, PCM is assumed to be defective. Replace PCM. Perform TEST VER-3A.