Dodge Ram Truck 1500-2500-3500. Manual — part 1266

P1594-CHARGING SYSTEM VOLTAGE TOO HIGH

9 - 1986

ENGINE - ELECTRICAL DIAGNOSTICS - SRT-10

DR/DH

P1594-CHARGING SYSTEM VOLTAGE TOO HIGH (CONTINUED)

For the Engine circuit diagram (Refer to 9 - ENGINE - SCHEMATICS AND DIAGRAMS).

For a complete wiring diagram Refer to Section 8W.

•

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

(K20) GENERATOR FIELD CONTROL CIRCUIT SHORTED TO GROUND

GENERATOR FIELD COIL SHORTED TO GROUND

BATTERY TEMPERATURE SENSOR

PCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)

Diagnostic Test

1.

CHARGING SYSTEM OPERATION

NOTE: Battery must be fully charged and be capable of passing a load test.

NOTE: Generator Belt tension and condition must be checked before continuing.
Ignition on, engine not running.

With the scan tool, read DTCs and the related Freeze Frame data then clear the DTCs.

With scan tool, actuate the Generator Field Driver.

With a 12-volt test light connected to ground, backprobe the (K20) Gen Field Control circuit in the back of Generator
Field harness connector.

Does the test light illuminate brightly and flash?

Yes

>> Go To 2

No

>> Refer to the INTERMITTENT CONDITION Diagnostic Procedure.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

DR/DH

ENGINE - ELECTRICAL DIAGNOSTICS - SRT-10

9 - 1987

P1594-CHARGING SYSTEM VOLTAGE TOO HIGH (CONTINUED)

2.

(K20) GEN FIELD CONTROL CIRCUIT SHORTED TO GROUND

Turn the ignition off.

Disconnect the C2 PCM harness connector.

Disconnect the Generator Field Harness connector.

Carefully inspect the related connectors for corrosion or spread termi-
nals before continuing.

Measure the resistance between ground and the (K20) Generator
Field Driver circuit at the Generator Field harness connector.

Is the resistance below 100 ohms?

Yes

>> Repair the short to ground in the (K20) Generator Field

Control circuit.

Perform the POWERTRAIN VERIFICATION TEST. (Refer
to 9 - ENGINE - STANDARD PROCEDURE)

No

>> Go To 3

3.

GENERATOR FIELD COIL SHORTED TO GROUND

Measure the resistance between ground and the Generator Field terminals on the Generator.

Is the resistance below 100 ohms?

Yes

>> Replace or repair the Generator Field Coil for a short to ground.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

No

>> Go To 4

4.

BATTERY TEMPERATURE SENSOR

Connect the PCM harness connectors and the Generator harness connector.

Ignition on, engine not running.

With the scan tool in Inputs/Outputs, read the Batt Temp Sensor value.

Using a thermometer measure under hood temperature near Battery tray.

Is the temperature within 10 deg of Battery temperature?

Yes

>> Go To 5

No

>> Replace the Battery Temperature Sensor.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

5.

PCM

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal
push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and
Ground circuits.

If there are no possible causes remaining, view repair.

Repair

Replace and program the Powertrain Control Module per Service Information.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

9 - 1988

ENGINE - ELECTRICAL DIAGNOSTICS - SRT-10

DR/DH

P1598-A/C PRESSURE SENSOR VOLTAGE TOO HIGH

DR/DH

ENGINE - ELECTRICAL DIAGNOSTICS - SRT-10

9 - 1989