Powertrain Control Module Controlled Generator Diagnosis. Chevrolet Cavalier 1998

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 1998 🢒 Cavalier 🢒 Engine 🢒 Engine Controls - 2.2L 🢒 Powertrain Control Module Controlled Generator Diagnosis

Engine Controls Components
IAC Valve, Generator, TR, Oil, and Coolant Switches
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice

Diagnosis

Use the following diagnostic table to diagnose the generator F and L circuit.

Use the following scan tool parameters when diagnosing the Powertrain Control Module (PCM) controlled generator.

Generator PWM - Range 0-100 Percent: The generator F terminal is a pulse width modulated (PWM) duty cycle or load input to the PCM from the generator. As the generator load increases, the PCM can sense the change and adjust the idle speed accordingly.

Generator L Terminal - Range Inactive/Active: The generator L terminal indicates whether the PCM is allowing the generator to operate. The PCM can disable the generator under certain conditions in order to ease starting. Active indicates that the PCM is allowing generator operation, while inactive indicates that the PCM is not allowing generator operation.

Circuit Description

The generator communicates to the Powertrain Control Module (PCM) over two lines, the L or lamp circuit and the F or Field circuit. The PCM uses the L circuit to monitor faults in the charging system. The F circuit is used by the PCM to monitor the duty cycle or load of the generator. The PCM will adjust the idle speed according to the generator load.

Diagnostic Aids

•

If the generator terminal F input circuit is shorted to voltage, the volts telltale lamp will operate normally. However, the scan tool Generator PWM will display a generator duty cycle near 10%. Check the generator terminal F input circuit for a short to voltage. If OK, the generator may be faulty, refer to the Charging System Check in Engine Electrical.

•	An Intermittent problem may be caused by a poor connection, rubbed through wire insulation, or a wire that is broken inside the insulation.

•	Any circuitry, that is suspected as causing the intermittent complaint, should be thoroughly checked for the following items:

-	Improper mating

-	Broken locks

-	Poor terminal to wiring connections

-	Physical damage to the wiring harness

Test Description

Numbers below refer to the step numbers on the Diagnostic Table.

The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.

If the volts telltale lamp is not operating, either a short circuit or the IPC is malfunctioning. This determines whether the L circuit, generator or IPC is malfunctioning.

If the charging system is not functioning, system voltage cannot be maintained above 12 V. Turning off all accessories assures that the system voltage is not being drawn down by an accessory that normally draws a large current.

Refer to Instrument Panel Cluster (IPC) Microprocessor portion of the service manual for replacement of the IPC.

When the engine is not running, the generator duty cycle will be displayed above 5%. If the generator duty cycle reads 0%, then the field circuit is either open or shorted to ground.

If the lamp circuit is not shorted to ground, the volts telltale lamp will go OFF until the next key cycle when the test light is probed into terminal B. Be careful not to probe terminal C with the test light, this will turn off the volts telltale lamp whether or not the lamp circuit is shorted.

The PCM supplies a voltage to the generator. If voltage is available to the generator at this terminal, then the PCM and wiring are OK.

Reprogram the replacement PCM. Perform the crankshaft position system variation procedure. Refer to PCM Replacement/Programming for PCM reprogramming and CKP System Variation Learn Procedure for the crankshaft position system variation procedure.

If no malfunctions have been found at this point, refer to Diagnostic Aids for additional checks and information.

PCM Controlled Generator

Step

Action

Value(s)

Yes

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check for 2.4L or Powertrain On Board Diagnostic (OBD) System Check for 2.2L

Turn ON the ignition switch leaving the engine OFF.

Is the volts telltale lamp on the IPC illuminated?

Go to Step 3

Go to Step 4

Start the engine.

Did the volts telltale lamp on the IPC turn OFF?

Go to Step 21

Go to Step 5

Turn OFF the ignition switch.
Disconnect the generator electrical connector.
Turn ON the ignition switch leaving the engine OFF.

Is the volts telltale lamp illuminated on the IPC?

Go to Step 6

Go to Step 7

Turn OFF all the accessories.
Install a scan tool.

Does the voltage read greater than the specified value?

12V

Go to Step 8

Go to Step 9

Connect a test light to ground.
Probe the lamp signal terminal of the generator electrical connector with the test light.

Does the test light illuminate?

Go to Step 10

Go to Step 11

Turn OFF the ignition switch.
Replace the Instrument Panel Cluster (IPC). Refer to Instrument Cluster Replacement in Instrument Panel, Guages and Console.

Is the action complete?

Go to Step 21

Does the Generator PWM value read greater than the specified value?

Go to Step 7

Go to Step 12

Turn OFF the ignition switch.
Disconnect the generator electrical connector.
Turn ON the ignition switch leaving the engine OFF.
Connect a test light to B+.
Probe the lamp signal terminal of the generator electrical connector with the test light.

Does the test light illuminate?

Go to Step 13

Go to Step 14

Repair the short to voltage in the lamp circuit.

Is the action complete?

Go to Step 21

Replace the generator. Refer to Charging System Check in Engine Electrical.

Is the action complete?

Go to Step 21

Turn OFF the engine.
Disconnect the generator electrical connector.
Turn ON the ignition switch leaving the engine OFF.
Connect a test light to B+.
Probe the field signal terminal of the generator electrical connector with the test light.

Does the test light illuminate?

Go to Step 15

Go to Step 16

Repair the short to ground in the lamp circuit.

Is the action complete?

Go to Step 21

Connect a DMM to ground.
Probe the lamp signal terminal of the generator electrical connector with the DMM.

Does the DMM read greater than the specified value?

4.5V

Go to Step 17

Go to Step 18

Repair the short to ground in the field circuit.

Is the action complete?

Go to Step 21

Check the field circuit for the following condition(s):

•	Poor electrical connection

•	Open circuit.

Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

Go to Step 21

Connect the DMM to ground.
Probe the battery terminal of the generator.

Does the DMM read the specified value?

B+

Go to Step 11

Go to Step 19

Check the lamp circuit for the following condition(s):

•	Poor electrical connection

•	Open circuit

Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

Go to Step 21

Go to Step 20

Check the battery terminal circuit for the following condition(s):

•	Poor electrical connection

•	Open circuit

Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

Go to Step 21

Check the PCM for poor electrical terminal connection(s).
If the electrical terminal connection(s) are ok, then replace the PCM. Refer to PCM Replacement .

Is the action completed?

Go to Step 21

Operate the vehicle within the conditions under which the original symptom was noted.

Does the system now operate properly?

System OK

Go to Step 2