Hummer H1 (2006+). Manual - part 75

OBD-144

On-Board Diagnostics

_____________________________________________

DTC P0300 Engine Misfire Detected

Circuit Description

The engine control module (ECM) adjusts the fuel delivery to each cylinder in order to minimize crankshaft speed changes. If the
ECM identifies a cylinder or cylinders requiring an excessive amount of fuel in order to maintain the correct crankshaft speed,
DTC P0300 will set.

Conditions for Setting the DTC

The fuel rate adjustment for more than one cylinder exceeds an acceptable value for more than 30 seconds.

Action Taken When the DTC Sets 

The control module illuminates the malfunction indicator lamp (MIL) on the second 
consecutive ignition cycle that the diagnostic runs and fails. 

The control module records the operating conditions at the time the diagnostic fails. The 
first time the diagnostic fails, the control module stores this information in the Failure 
Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the 
control module records the operating conditions at the time of the failure. The control 
module writes the operating conditions to the Freeze Frame and updates the Failure 
Records. 

Conditions for Clearing the MIL/DTC 

• The control module turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail. 

• A current DTC, Last Test Failed, clears when the diagnostic runs and passes. 

• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related 

diagnostic.

• Use a scan tool in order to clear the MIL and the DTC. 

Diagnostic Aids

A misfire with no other DTCs will be caused by an engine mechanical or fuel injector problem.

Step

Action

Value(s)

Yes

No

    1

NOTE: Before clearing DTC(s) use the scan tool “Capture info”
to record Freeze Frame and Failure Records for reference, as data
will be lost when “Clear Info” function is used 

Was the “On-Board Diagnostic (OBD) System Check” per-
formed?

Go to step 2.

Go to OBD Sys-

tem Check.

    2

Are any other DTCs set?

Go to the appli-

cable DTC 

table.

Intermittent Go 

To Diagnostic 

Aids

_____________________________________________

 On-Board Diagnostics  OBD-145

5745804

DTC P0301-P0308 Cylinder Misfire Detected

Circuit Description

The engine control module (ECM) monitors changes in crankshaft speed using inputs from the crankshaft position (CKP) sensor
and the fuel injection control module (FICM). The ECM adjusts the fuel delivery to each cylinder in order to minimize crankshaft
speed changes. This DTC will set when the ECM identifies a cylinder or cylinders requiring an excessive amount of fuel in order to
maintain the correct crankshaft speed.

Conditions for Setting the DTC

The fuel rate adjustment for a cylinder exceeds an acceptable value for more than 30 seconds.

Action Taken When the DTC Sets 

• The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diag-

nostic runs and fails. 

• The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the

control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecu-
tive ignition cycle, the control module records the operating conditions at the time of the failure. The control module 
writes the operating conditions to the Freeze Frame and updates the Failure Records. 

Conditions for Clearing the MIL/DTC 

• The control module turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail. 

• A current DTC, Last Test Failed, clears when the diagnostic runs and passes. 

• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related 

diagnostic.

• Use a scan tool in order to clear the MIL and the DTC. 

Diagnostic Aids

A misfire with no other DTCs will be caused by an engine mechanical or fuel injector problem.

Step

Action

Value(s)

Yes

No

    1

NOTE: Before clearing DTC(s) use the scan tool “Capture info”
to record Freeze Frame and Failure Records for reference, as data
will be lost when “Clear Info” function is used 

Was the “On-Board Diagnostic (OBD) System Check” per-
formed?

Go to step 2.

Go to OBD Sys-

tem Check.

    2

Are there any other DTCs set?

Go to the appli-

cable DTC 

table.

Intermittent Go 

To Diagnostic 

Aids

OBD-146

On-Board Diagnostics

_____________________________________________

DTC P0335 Crankshaft Position (CKP) Sensor Circuit (Figure OBD-42)

Figure OBD-42:   Crankshaft Position (CKP) Sensor Circuit

Circuit Description

The hall effect crankshaft position (CKP) sensor signal indicates the crankshaft speed and position. There are 57 teeth on the front
of the crankshaft sprocket, plus a sync gap. The CKP sensor will output an ON-OFF pulse as each window passes the sensing ele-
ment. The CKP sensor is connected directly to the engine control module (ECM) by the following circuits:

• The 12-volt reference circuit 

• The low reference circuit 

• The CKP sensor signal circuit 

Conditions for Setting the DTC

The ECM determines no signal from the CKP sensor for less than 8 seconds.

Action Taken When the DTC Sets 

• The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. 

• The control module records the operating conditions at the time the diagnostic fails. The control module stores this informa-

tion in the Freeze Frame/Failure Records. 

_____________________________________________

 On-Board Diagnostics  OBD-147

5745804

Conditions for Clearing the MIL/DTC 

• The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic 

runs and does not fail. 

• A current DTC, Last Test Failed, clears when the diagnostic runs and passes. 

• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related 

diagnostic.

• Clear the MIL and the DTC with a scan tool. 

Step

Action

Value(s)

Yes

No

    1

NOTE: Before clearing DTC(s) use the scan tool “Capture info”
to record Freeze Frame and Failure Records for reference, as data
will be lost when “Clear Info” function is used 

Was the “On-Board Diagnostic (OBD) System Check” per-
formed?

Go to step 2.

Go to OBD Sys-

tem Check.

    2

Attempt to start the engine.

Does the engine start and run?

Intermittent Go 

To Diagnostic 

Aids

Go to Step 3 

    3

1.

Turn OFF the ignition.

2.

Disconnect the crankshaft position (CKP) sensor harness 
connector.

3.

Turn ON the ignition, with the engine OFF.

4.

Connect a test lamp between the 12-volt reference circuit 
257 (LG) pin A of the CKP harness connector and a good 
ground.

Does the test lamp illuminate?

B+

Go to Step 4 

Go to Step 7 

    4

1.

Turn OFF the ignition.

2.

Connect a jumper wire between each of the terminals in the 
CKP sensor harness connector and the corresponding termi-
nal at the CKP sensor. 

3.

Turn ON the ignition, with the engine OFF.

4.

Measure the voltage from the low reference circuit 258 (YL/
BK) pin B of the CKP sensor at the jumper wire terminal to a 
good ground with a DVOM. 

Is the voltage more than the specified value?

0.2 Volts

Go to Step 6 

Go to Step 5 

    5

1.

Turn OFF the ignition.

2.

Remove the jumper wires from the CKP sensor harness con-
nector.

3.

Turn ON the ignition, with the engine OFF.

4.

Observe the crank signal present parameter with a scan tool.

5.

With a fused jumper wire connected to the signal circuit 256 
(BL) pin C of the CKP sensor harness connector, momen-
tarily and repeatedly probe B+.

Does the crank signal present parameter change when the jumper
wire contacts B+ repeatedly?

Go to Step 9 

Go to Step 8 

    6

Test the low reference circuit 258 (YL/BK) for an open or high
resistance between C77 pin 43 and pin B of the CKP sensor con-
nector.

Did you find and correct the condition?

Go to Step 16 

Go to Step 11