P1637

DTC P1637

CIRCUIT DESCRIPTION
The powertrain control module (PCM) uses the generator turn ON signal 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 generator turn ON signal 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 generator turn ON signal circuit. The PCM has fault detection circuitry which monitors the state of the generator turn ON signal circuit. If the fault detection circuit senses a voltage other than what is expected, this DTC will set. The voltage regulator also contains fault detection circuitry. If the regulator detects a problem, the regulator will ground the generator turn on signal circuit, pulling the voltage low. This also causes the PCM to set the DTC.

CONDITIONS FOR RUNNING THE DTC

Key ON Test
- The Key is in the ON position for 5 seconds.
- The engine is OFF.

Engine Run Test
- The engine is running.
- The engine speed is less than 3,000 RPM.

CONDITIONS FOR SETTING THE DTC

Key ON Test
- The ECM detects a high signal voltage on the generator turn on signal circuit for at least 5 seconds.
- The engine must be started.

During the RUN test, the ECM detects a low signal voltage on the generator turn on signal circuit for at least 5 seconds.

ACTION TAKEN WHEN THE DTC SETS
- The ECM sends a class 2 message to the IPC to illuminate the charge indicator and/or turn on a message.
- The ECM will not illuminate the malfunction indicator lamp (MIL).
- The ECM will store the conditions present when the DTC set as Fail Records data only.

CONDITIONS FOR CLEARING THE MIL/DTC
- The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
- The DTC can be cleared by using the scan tool Clear DTC Information function.

TEST

Steps 1-4:

Steps 5-11: