2001 Chevrolet/Geo Camaro  

DTC P0620

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.

When this DTC sets, the PCM sends a class 2 serial data message to the IPC illuminating the Charge indicator lamp.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC
Action Taken When the DTC Sets
Conditions for Clearing the MIL/DTC

Step

Action

Value(s)

Yes

No

Schematic Reference: Starting and Charging Schematics

1

Did you perform the Engine Electrical Diagnostic System Check?

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Go to Step 2

Go to Diagnostic System Check - Engine Electrical

2
  1. Turn OFF the ignition.
  2. Disconnect the Generator.
  3. Measure the voltage between the generator turn-on signal circuit and ground.
  4. Start the engine.
  5. Command the Generator ON and OFF with the scan tool.

Does the voltage change between the two indicated values?

0.0-5.0 V

Go to Testing for Intermittent and Poor Connections in Wiring Systems

Go to Step 3

3

Test the generator turn on signal circuit for a high resistance or open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 6

Go to Step 4

4

Inspect for poor connections at the harness connector of the PCM. Refer to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 6

Go to Step 5

5

Important

The replacement PCM must be programmed.

Replace the PCM. Refer to Powertrain Control Module (PCM) Programming in Engine Controls-3.8L or Powertrain Control Module (PCM) Replacement in Engine Controls-3.8L.

Is the action complete?

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Go to Step 6

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6
  1. Review and record the scan tool Fail Records data.
  2. Clear any DTCs.
  3. Operate the vehicle within the Fail Records conditions as noted.
  4. Using a scan tool, monitor the Specific DTC info for this DTC.

Does the scan tool indicate that this DTC failed this ignition?

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Go to Step 2

System OK