P0620

Diagnostic Chart (Part 1 Of 2):

Diagnostic Chart (Part 2 Of 2):

Refer to Engine Controls Schematics Engine Oil Level Pressure and Power Steering Pressure Switch Inputs.

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) uses the L-terminal circuit to control the generator. A high side driver within the PCM allows the PCM to turn the generator ON and OFF. When generator operation is desired, the PCM sends a 5 volt signal to the voltage regulator via the L-terminal circuit. This causes the voltage regulator to begin controlling the generator field circuit. Once the generator is enabled by the PCM, the voltage regulator controls generator output independently of the PCM. Under certain operating conditions, the PCM can turn OFF the generator by turning OFF the 5 volt signal on the L-terminal circuit. The PCM has fault detection circuitry which monitors the state of the L-terminal circuit. If the fault detection circuit senses a voltage other than what is expected, this Diagnostic Trouble Code (DTC) will set. The voltage regulator also contains fault detection circuitry. If the regulator detects a problem, the regulator will ground the L-terminal circuit, pulling the voltage low. This also causes the PCM to set the DTC.

The PCM receives generator output, or electrical load, feedback via the F-terminal circuit. The voltage regulator generates a Pulse Width Modulation (PWM) signal on the field control circuit. The regulator varies the pulse width of this signal in order to control generator output. This signal is also sent to the PCM via the F-terminal circuit. The pulse width of the signal is proportional to generator output. The PCM expects generator output to be within a predetermined range under certain operating conditions. If the PCM detects that the PWM signal on the F-terminal circuit is not within the expected range, this DTC will set.

When this DTC sets, the PCM sends a class 2 serial data message to the Instrument Panel (IP) illuminating the charge indicator lamp.

CONDITIONS FOR RUNNING THE DTC
The engine is running.

CONDITIONS FOR SETTING THE DTC
^ The L-terminal voltage is low while the PCM is commanding the generator ON.
^ The above condition is present for more than 30 seconds.

OR

^ The F-terminal PWM is less than 5 percent.
^ The engine RPM is less than 2,500.
^ The above conditions are present for more than 30 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM stores the DTC information into memory when the diagnostic runs and fails.
^ The Malfunction Indicator Lamp (MIL) will not illuminate.
^ The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ A History DTC will clear after forty consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
^ The current DTC will clear when the diagnostic runs and does not fail.
^ Use a scan tool in order to clear the MIL diagnostic trouble code.
^ Interrupting the PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Powertrain Control Module (PCM) description, Clearing Diagnostic Trouble Codes.

DIAGNOSTIC AIDS

NOTE: Refer to Connector Test Adapter Kit J 35616-A Notice in Service Precautions.

If the problem is intermittent, refer to Intermittent Conditions. Intermittent Conditions

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
10. This vehicle is equipped with a PCM that utilizes and Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.