Hummer H2. Manual - part 1160

z

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

Conditions for Clearing the MIL/DTC 

z

The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.  

z

The DTC can be cleared by using the scan tool Clear DTC Information function.  

Diagnostic Aids 

Ignition system DTCs set with the ignition switch in the START position if the starter relay or the starter is 
inoperative. When the PCM enables starter operation, the PCM also initiates the diagnostic test routines for 
DTC P0335. If a condition exists which prevents the engine from cranking, the PCM will not receive signal 
input from the CKP and CMP sensors, and the DTCs will set. 

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may assist in diagnosing the 
condition. The information may help determine how often the condition that set the DTC occurs. 

Test Description 

The number(s) below refer to the step number(s) on the diagnostic table. 

2: Listen for an audible click when the Start 1 relay operates. Turn the ignition switch back and forth 
from the ON to START positions. Repeat this as necessary.  

3: Tests for voltage at the coil side of the Start 1 relay. The PCM IGN fuse supplies power to the coil side 
of the Start 1 relay.  

4: Verifies that the PCM is providing ground to the Start 1 relay.  

5: Tests if ground is constantly being applied to the Start 1 relay.  

DTC P0615 

Step

Action

Yes

No

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

1

Did you perform the Engine Electrical 
Diagnostic System Check?

Go to Step 2

Go to Diagnostic 

System Check - 

Engine Electrical

2

1. Install a scan tool.  

2. Turn ON the ignition, with the engine 

OFF.  

3. Turn the ignition back and forth from the 

ON to START positions.  

Does the Start 1 relay turn ON and OFF with 
each command?

Go to Testing for 

Intermittent Conditions 

and Poor Connections in 

Wiring Systems

Go to Step 3

1. Turn OFF the ignition.  

 

2004 Hummer H2 

2004 ELECTRICAL Engine Electrical - Hummer H2

  

3

2. Disconnect the Start 1 relay.  

3. Turn ON the ignition, with the engine 

OFF.  

4. Probe the battery positive voltage of the 

Start 1 relay coil circuit with a test lamp 
that is connected to a good ground.  

Does the test lamp illuminate?

Go to Step 4

Go to Step 8

4

1. Connect a test lamp between the control 

circuit of the Start 1 relay and the battery 
positive voltage of the Start 1 relay coil 
circuit.  

2. Turn the ignition back and forth from the 

ON to START positions.  

Does the test lamp turn ON and OFF with each 
command?

Go to Step 6

Go to Step 5

5

Test the control circuit of the Start 1 relay for a 
short to voltage or an 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 7

6

Inspect for poor connections at the Start 1 relay. 
Refer to Testing for Intermittent Conditions 
and Poor Connections and Connector Repairs
in Wiring Systems. 
Did you find and correct the condition?

Go to Step 11

Go to Step 9

7

Inspect for poor connections at the PCM. Refer 
to Testing for Intermittent Conditions and 
Poor Connections and Connector Repairs in 
Wiring Systems. 
Did you find and correct the condition?

Go to Step 11

Go to Step 10

8

Repair the battery positive voltage circuit of the 
Start 1 relay. Refer to Connector Repairs in 
Wiring Systems. 
Did you complete the repair?

Go to Step 11

-

9

Replace the Start 1 relay. Refer to Relay 
Replacement (Within an Electrical Center) or 
Relay Replacement (Attached to Wire 
Harness) in Wiring Systems. 
Did you complete the replacement?

Go to Step 11

-

10

IMPORTANT:

The replacement PCM must be programmed.

 

2004 Hummer H2 

2004 ELECTRICAL Engine Electrical - Hummer H2

  

DTC P0622 

Circuit Description 

The 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 IPC to illuminate the 
charge indicator. 

or  

Conditions for Running the DTC 

Key ON Test 

z

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

z

The key is in the RUN position.  

z

The engine is not running.  

Run Test 

Replace the PCM. Refer to Powertrain Control 
Module (PCM) Replacement in Engine 
Controls.Did you complete the replacement?

Go to Step 11

-

11

1. Review and record the scan tool Fail 

Records data.  

2. Use the scan tool in order to clear the 

DTC.  

3. Operate the vehicle within the Conditions 

for Running the DTC as specified in the 
supporting text.  

4. Using the scan tool, observe the Specific 

DTC Information for DTC P0615 until the 
test runs.  

Does the scan tool indicate that DTC P0615 
failed this ignition?

Go to Step 2

System OK

 

2004 Hummer H2 

2004 ELECTRICAL Engine Electrical - Hummer H2

  

z

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

z

The engine is less than 3000 RPM.  

Conditions for Setting the DTC 

z

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

z

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 

z

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

z

The malfunction indicator lamp (MIL) will not illuminate.  

Conditions for Clearing the DTC 

z

The Conditions for Setting the DTC are no longer present.  

z

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

z

The Powertrain Control Module (PCM) receives the clear code command from the scan tool.  

DTC P0622 

Step

Action

Value

(s)

Yes

No

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

1

Did you perform the Engine Electrical 
Diagnostic System Check?

-

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 GEN 

- F Terminal parameter in the 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

1. Turn OFF the ignition.  

2. Disconnect the generator 

connector.  

 

2004 Hummer H2 

2004 ELECTRICAL Engine Electrical - Hummer H2