2014 Jeep Wrangler JK Factory Service Manual 28 - DTC-Based Diagnostics

P0622-GENERATOR FIELD CONTROL CIRCUIT

Special Tools: Click to display a list of tools used in this procedure

For a complete wiring diagram, refer to the Wiring Information.





Theory of Operation

The Powertrain Control Module (PCM) uses the Generator field duty cycle signal circuit or F-terminal circuit, to monitor the duty cycle of the generator. The Generator field duty cycle signal circuit connects to high side of the field windings in the Generator. A Pulse Width Modulated (PWM) high side driver in the voltage regulator turns the field windings ON and OFF. The PCM uses the PWM signal input to determine the Generator load on the engine. This allows the PCM to adjust the idle speed to compensate for high electrical loads. The PCM monitors the status of the generator field duty cycle signal circuit. When the key is in the RUN position and the engine is OFF, the PCM should detect a duty cycle near 0 percent. However, when the engine is running, the duty cycle should be between 5-95 percent.



Possible Causes

(K20) GEN FIELD CONTROL CIRCUIT SHORTED TO BATTERY VOLTAGE
(K20) GEN FIELD CONTROL CIRCUIT OPEN
(K20) GEN FIELD CONTROL CIRCUIT SHORTED TO GROUND
GENERATOR
POWERTRAIN CONTROL MODULE (PCM)

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).


1. ACTIVE DIAGNOSTIC TROUBLE CODE (DTC)

1. Start the engine and allow it to reach operating temperature.

WARNING:

When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.

2. Increase engine speed by pressing the accelerator pedal. Do not exceed 3500 rpm.
3. Using the scan tool, read the active DTCs.


Is the DTC Active at this time?

Yes


No


2. GENERATOR OPERATION
1. Turn the ignition off.
2. Disconnect the Generator harness connector.
3. Using a 12-Volt test light connected to ground, probe the (K20) Generator Field Control circuit in the Generator Field harness connector.
4. Ignition on, engine not running.


NOTE: The DTC needs to be cleared before actuating the Solenoid, if the DTC is not cleared, the Solenoid may not be allowed to actuate.
5. With the scan tool, actuate the Generator Field Driver.

NOTE: The test light should be illuminated and bright proportional to the maximum duty cycle allowed by the scan tool. For example, if the scan tool allows 100% actuation, the brightness should be as bright as a direct connection to the battery. If the scan tool allows a maximum 25% actuation, the brightness should be 25% as bright as a direct connection to the battery.


Does the test light illuminate brightly and flash on and off?

Yes


No


3. (K20) GEN FIELD CIRCUIT SHORTED TO VOLTAGE
1. Turn the ignition off.
2. Disconnect the PCM C2 harness connector.
3. Ignition on, engine not running.
4. Measure the voltage on the (K20) Gen Field Control circuit in the Generator Field harness connector.


Is there any voltage present?

Yes


No


4. CHECK THE (K20) GEN FIELD CIRCUIT FOR AN OPEN/HIGH RESISTANCE

1. Turn the ignition off.

CAUTION:

Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install the GPEC Diagnostic Adaptor to perform the diagnosis.

2. Connect the Adapter, GPEC Diagnostic 10436 .
3. Measure the resistance of the (K20) Gen Field Control circuit between the Generator harness connector and the GPEC Adaptor.


Is the resistance below 5.0 Ohms?

Yes


No


5. CHECK THE (K20) GEN FIELD CIRCUIT FOR A SHORT TO GROUND
1. Measure the resistance between ground and the (K20) Gen Field Control circuit in the Generator Field harness connector.


Is the resistance above 10k Ohms?

Yes


No


6. POWERTRAIN CONTROL MODULE (PCM)

1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Generator and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the Generator and Powertrain Control Module connectors.
4. Perform any Technical Service Bulletins that may apply.


Were there any problems found?

Yes


No