GM Service Manual Online
For 1990-2009 cars only

Schematics

Refer to

Generator Controls


Object Number: 585326  Size: FS
.

Circuit Description

The PCM uses the generator turn on signal circuit to control the load of the generator on the engine. A high side driver in the PCM applies a voltage to the voltage regulator. This signals the voltage regulator to turn the field circuit ON and OFF. When the PCM turns ON the high side driver, the voltage regulator turns ON the field circuit. When the PCM turns OFF the high side driver, the voltage regulator turns OFF the field circuit.

The PCM monitors the state of the generator turn on signal circuit. The PCM should detect a high generator turn on signal circuit voltage when the engine in running, or when the charging system malfunctions. When this ocures , the PCM will send a class 2 serial data message to the IPC to illuminate the BATTERY NOT CHARGING display in the DIC and set DTC B1911.

Conditions for Running the DTC

    • No generator, CKP sensors, or CMP sensor DTCs are set.
    • The engine is running.

Conditions for Setting the DTC

    • During the key ON test, the PCM detects a high signal voltage on the generator turn on signal circuit for at least 1 seconds.
    • DTC B1982 is not set.

Action Taken When the DTC Sets

    • The PCM will not illuminate the Malfunction Indicator Lamp (MIL)
    • The PCM will store the conditions present when the DTC set as Fail Records data only.

Conditions for Clearing the 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.

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check - Starting and Charging?

--

Go to Step 2

Go to Diagnostic System Check - Engine Electrical

2

  1. Install a scan tool.
  2. Start the engine.
  3. With a scan tool, observe the Generator PWM parameter in the PCM data list .

Does the scan tool indicate that the Generator PWM parameter is within the specified range?

5% - 95%

Go to Step 3

Go to Step 4

3

With the scan tool command the generator L terminal OFF.

Does the Generator PWM equal the specified value?

0%

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Disconnect the generator harness connector.
  3. Start the engine.
  4. Measure the voltage between the generator turn on signal circuit and a known good ground.
  5. With the scan tool command the generator ON and OFF.

Is the voltage equal to the first value with the generator OFF and equal to the second value with the generator ON?

0.0 V

5.0 V

Go to Step 5

Go to Step 6

5

  1. Turn ON the ignition, leaving the engine OFF.
  2. Connect a test lamp to battery positive voltage and repeatedly probe the generator field duty cycle signal circuit in the harness connector while monitoring the Generator PWM on the scan tool.

Is the Generator PWM display affected?

--

Go to Step 8

Go to Step 7

6

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

Did you find and correct the condition?

--

Go to Step 11

Go to Step 9

7

Test the generator field duty cycle signal circuit for a short or open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 11

Go to Step 9

8

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

Did you find and correct the condition?

--

Go to Step 11

Go to Diagnostic System Check - Engine Electrical

9

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

Did you find and correct the condition?

--

Go to Step 11

Go to Step 10

10

Replace the IPC. Refer to Instrument Cluster Replacement in Instrument Panel Gauges and Console.

Did you complete the replacement?

--

Go to Step 11

--

11

  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the conditions for running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK