Hummer H2. Manual - part 1638

„

The HO2S bank 1 sensor 1 and HO2S bank 2 sensor 1 is more than 600 mV.  

Action Taken When the DTC Sets 

z

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

z

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 

z

The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles 
that the diagnostic runs and does not fail.  

z

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

z

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

z

Clear the MIL and the DTC with a scan tool.  

Test Description 

The numbers below refer to the step numbers on the diagnostic table. 

2: If the voltage does not change more than the specified value, the condition is present.  

DTC P0136 or P0156 

Step

Action

Value

(s)

Yes

No

Schematic Reference:Engine Controls Schematics 
Connector End View Reference:Engine Controls Connector End Views or Powertrain Control 
Module (PCM) Connector End Views

1

Did you perform the Diagnostic System Check-Engine 
Controls?

-

Go to Step 2

Go to Diagnostic 

System Check - 

Engine Controls

2

1. Start the engine.  

2. Allow the engine to reach operating temperature. 

Refer to Scan Tool Data List .  

3. Operate the engine at 1,500 RPM for 30 seconds. 

4. While observing the affected HO2S voltage 

parameter with a scan tool, quickly cycle the 
throttle from closed throttle to wide open throttle, 
3 times.  

200 
mV

 

2004 Hummer H2 

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0068 To DTC P0141/P0161) - 4.8L, 5.3L, and 6.0L - 

Hummer H2

  

Did the HO2S voltage parameter change more than the 
specified value?

Go to Step 3

Go to Step 4

3

1. Observe the Freeze Frame/Failure Records for 

this DTC.  

2. Turn OFF the ignition for 30 seconds.  

3. Start the engine.  

4. Operate the vehicle within the Conditions for 

Running the DTC. You may also operate the 
vehicle within the conditions that you observed 
from the Freeze Frame/Failure Records.  

Did the DTC fail this ignition?

-

Go to Step 4

Go to 

Intermittent 

Conditions

4

1. Turn OFF the ignition.  

2. Disconnect the affected heated oxygen sensor 

(HO2S).  

3. Turn ON the ignition, with the engine OFF.  

4. Observe the HO2S voltage parameter with a scan 

tool.  

Is the HO2S voltage parameter less than the specified 
value?

100 
mV

Go to Step 6

Go to Step 5

5

Observe the HO2S voltage parameter with a scan tool.
Is the HO2S voltage parameter more than the specified 
value?

800 
mV

Go to Step 7

Go to Step 8

6

Test the HO2S high signal circuit for a short to ground. 
Refer to Circuit Testing and Wiring Repairs in 
Wiring Systems. 
Did you find and correct the condition?

-

Go to Step 20

Go to Step 9

7

Test the HO2S high signal circuit for a short to voltage. 
Refer to Circuit Testing and Wiring Repairs in 
Wiring Systems.Did you find and correct the 
condition?

IMPORTANT:

The sensor may be damaged if the circuit is shorted 
to a voltage source.

-

Go to Step 20

Go to Step 17

8

Measure the voltage from the low signal circuit of the 
HO2S harness connector on the engine harness side to 
a good ground with a DMM. Refer to Circuit Testing 
in Wiring Systems. 
Is the voltage more than the specified value?

2 V

Go to Step 10

Go to Step 11

9

Test the HO2S high signal circuit for a short to the 
HO2S low signal circuit. Refer to Circuit Testing and 

-

 

2004 Hummer H2 

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0068 To DTC P0141/P0161) - 4.8L, 5.3L, and 6.0L - 

Hummer H2

  

Wiring Repairs in Wiring Systems. 
Did you find and correct the condition?

Go to Step 20

Go to Step 17

10

Test the HO2S low signal circuit for a short to voltage. 
Refer to Circuit Testing and Wiring Repairs in 
Wiring Systems. 
Did you find and correct the condition?

-

Go to Step 20

Go to Step 17

11

1. Connect a 3-amp fused jumper wire between the 

high signal circuit of the HO2S harness 
connector on the engine harness side and a good 
ground.  

2. Observe the HO2S voltage parameter with a scan 

tool.  

Is the HO2S voltage parameter less than the specified 
value?

100 
mV

Go to Step 12

Go to Step 14

12

1. Remove the jumper wire from the previous step.  

2. Connect a 3-amp fused jumper wire between the 

high signal circuit of the HO2S harness 
connector on the engine harness side and the low 
signal circuit of the HO2S harness connector on 
the engine harness side.  

3. Observe the HO2S voltage parameter with a scan 

tool.  

Is the HO2S voltage parameter less than the specified 
value?

100 
mV

Go to Step 15

Go to Step 13

13

Test the HO2S low signal circuit for an open or high 
resistance. Refer to Circuit Testing and Wiring 
Repairs in Wiring Systems. 
Did you find and correct the condition?

-

Go to Step 20

Go to Step 17

14

Test the HO2S high signal circuit for an open or high 
resistance. Refer to Circuit Testing and Wiring 
Repairs in Wiring Systems. 
Did you find and correct the condition?

-

Go to Step 20

Go to Step 17

1. The HO2S may be detecting a rich exhaust 

condition, a lean exhaust condition, or the HO2S 
may be contaminated. Inspect for the following 
conditions: 

NOTE:

Refer to Silicon Contamination of 
Heated Oxygen Sensors Notice in 
Cautions and Notices.

 

2004 Hummer H2 

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0068 To DTC P0141/P0161) - 4.8L, 5.3L, and 6.0L - 

Hummer H2

  

15

z

A silicon contaminated HO2S  

z

Any water intrusion into the HO2S 
connector  

z

An exhaust leak between the HO2S and 
the engine  

z

Any vacuum leaks  

z

Engine oil contaminated with fuel  

z

An incorrect fuel pressure-Refer to Fuel 
System Diagnosis .  

z

Any lean or rich fuel injectors-Refer to 
Fuel Injector Balance Test with Tech 2 . 

z

An inaccurate mass air flow (MAF) 
sensor-Refer to Scan Tool Data List .  

2. Repair any of the above or similar engine 

conditions as necessary.  

Did you find and correct the condition?

-

Go to Step 20

Go to Step 16

16

Test for shorted terminals and for poor connections at 
the HO2S. 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 20

Go to Step 18

17

Test for shorted terminals and for poor connections at 
the powertrain control module (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 20

Go to Step 19

18

Replace the affected HO2S. Refer to Heated Oxygen 
Sensor (HO2S) Replacement Bank 1 Sensor 2 or 
Heated Oxygen Sensor (HO2S) Replacement Bank 2 
Sensor 2 . 
Did you complete the replacement?

-

Go to Step 20

-

19

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

-

Go to Step 20

-

20

1. Clear the DTCs with a scan tool.  

2. Turn OFF the ignition for 30 seconds.  

3. Start the engine.  

4. Operate the vehicle within the Conditions for 

Running the DTC. You may also operate the 
vehicle within the conditions that you observed 
from the Freeze Frame/Failure Records.  

-

 

2004 Hummer H2 

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0068 To DTC P0141/P0161) - 4.8L, 5.3L, and 6.0L - 

Hummer H2