P0620

Refer to Engine Controls Schematics.

Diagnostic Chart:

CIRCUIT DESCRIPTION
The PCM Output (L) terminal to the alternator determines when the alternator will be turned OFF. The PCM Output (L) terminal is ON under all normal vehicle operating conditions except during low RPM conditions. The alternator is turned off during low RPM conditions to remove excess load from the engine.

The PCM Input Field (F) terminal from the alternator provides a 400 Hz PWM signal to the PCM. The duty cycle of the F terminal mimics the duty cycle of the field coils in the alternator. Thus, the F terminal duty cycle indicates the relative electrical load on the alternator.

The alternator telltale lamp will illuminate any time the ignition is on and engine is not running. The telltale will go out after the engine is running and the alternator is putting out the desired amperage.

CONDITIONS FOR RUNNING THE DTC
^ The engine speed is below 1000 RPM to run Low Duty Cycle Test.
OR
The engine speed is above 1300 RPM to run High Duty Cycle Test.
^ The voltage telltale is ON.

CONDITIONS FOR SETTING THE DTC
^ (L) terminal voltage is low while the PCM is commanding the generator on.
^ The above condition is present for more than 10 seconds.
OR
^ (F) terminal PWM is less than 10 percent for 30 seconds or more than 95 percent for 60 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM will illuminate the Malfunction Indicator Lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed.
^ The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data.
^ If the misfire is determined to be catalyst damaging, the PCM will flash the MIL.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed.
^ The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC can be cleared by using a scan tool.

DIAGNOSTIC AIDS
Inspect for the following conditions:

IMPORTANT: Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.

^ Poor terminal connection-Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Use a corresponding mating terminal to test for proper tension.
^ Damaged harness-Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault.
^ PCM and engine grounds for clean and secure connections

If the DTC is determined to be intermittent, reviewing the Failure Records can be useful in determining when the DTC was last set.

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