Hummer H3. Manual — part 5

DTC P0622

Circuit Description

The powertrain control module (PCM) uses the generator field duty cycle signal circuit to
monitor the duty cycle of the generator. The generator field duty cycle signal circuit connects to
the high side of the field winding in the generator. A pulse width modulated (PWM) high side
driver in the voltage regulator turns the field winding ON and OFF. The PCM uses the PWM
signal input to determine the generator load on the engine. This allows the PCM to adjust the idle
speed to compensate for high electrical loads.

The PCM monitors the state of the generator field duty cycle signal circuit. When the key is in the
RUN position and the engine is OFF, the PCM should detect a duty cycle near 0 percent.
However, when the engine is running, the duty cycle should be between 5 percent and 100
percent. The PCM monitors the PWM signal using a key ON test and a RUN test. During the
tests, if the PCM detects an out of range PWM signal, DTC P0622 will set. When the DTC sets,
the PCM will send a class 2 serial data message to the instrument panel cluster (IPC) to illuminate
the charge indicator.

DTC Descriptor

This diagnostic procedure supports the following DTC:

Systems.
Did you find and correct the condition?

Go to Step 6

Go to Step 5

5

Replace the PCM. Refer to Control Module
References in Computer/Integrating Systems for
replacement, setup, and programming.
Did you compete the replacement?

Go to Step 6

-

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?

Go to Step 2

System OK

2006 Hummer H3

2006 ENGINE Engine Electrical - H3

DTC P0622 Generator F-Terimal Circuit

Conditions for Running the DTC

Key ON Test

No generator, crankshaft position (CKP) sensors, or camshaft position (CMP) sensor DTCs
are set.

The key is in the RUN position.

The engine is not running.

Run Test

No generator, CKP sensors, or CMP sensor DTCs are set.

The engine is less than 3,000 RPM.

Conditions for Setting the DTC

During the ignition ON test, the PCM detects a PWM signal is out of range.

During the RUN test, the PCM detects a PWM signal less then 5 percent for more than 6
seconds.

Action Taken When the DTC Sets

The PCM will store the conditions present when the DTC set as Fail Records data only.

The malfunction indicator lamp (MIL) will not illuminate.

Conditions for Clearing the DTC

The Conditions for Setting the DTC are no longer present.

A history DTC will clear after 40 malfunction-free ignition cycles.

The PCM receives the clear code command from the scan tool.

DTC P0622

Step

Action

Values

Yes

No

Schematic Reference: Starting and Charging Schematics
Connector End View Reference: Engine Electrical Connector End Views

Did you perform the Diagnostic System
Check - Vehicle?

Go to
Diagnostic
System

2006 Hummer H3

2006 ENGINE Engine Electrical - H3

1

-

Go to Step 2

Check -
Vehicle in
Vehicle DTC
Information

2

1. Install a scan tool.

2. Start the engine.

3. With a scan tool, observe the GEN -

F Terminal parameter in the
powertrain control module (PCM)
data list.

Does the scan tool indicate that the GEN -
F Terminal parameter is within the
specified range?

5-95%

Go to Step 3 Go to Step 4

3

With the scan tool command the generator
OFF.
Does the GEN - F Terminal 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 connector.

3. Connect test lamp to battery positive

voltage.

4. Turn ON the ignition, with the

engine OFF.

5. Probe the F-Terminal in the

generator connector.

6. Observe the GEN - F Terminal

Signal parameter in the PCM data
list.

Is the GEN - F Terminal Signal parameter
near the specified value?

100%

Go to
Charging
System Test

Go to Step 5

Test the generator field duty cycle signal

2006 Hummer H3

2006 ENGINE Engine Electrical - H3

SYMPTOMS - ENGINE ELECTRICAL

Perform Diagnostic System Check - Vehicle in Vehicle DTC Information, before using
the Symptom Tables in order to verify that all of the following are true:

1. There are no DTCs set.

2. The control modules can communicate via the serial data link.

Review the system operation in order to familiarize yourself with the system functions.
Refer to one of the following system operations:

Battery Description and Operation

Starting System Description and Operation

5

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 8 Go to Step 6

6

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?

-

Go to Step 8 Go to Step 7

7

Replace the PCM. Refer to Control
Module References in
Computer/Integrating Systems for
replacement, setup, and programming.
Did you compete the replacement?

-

Go to Step 8

-

8

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?

-

Go to Step 2 System OK

IMPORTANT: The following steps must be completed before using the symptom

tables.

2006 Hummer H3

2006 ENGINE Engine Electrical - H3