Hummer H2. Manual - part 1516

2004 ENGINE PERFORMANCE

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

H2 

ENGINE CONTROLS DIAGNOSIS (DTC P0068 TO DTC P0141/P0161) 

DTC P0068 

Circuit Description 

The powertrain control module (PCM) uses the following readings to calculate the predicted mass air flow 
(MAF) rate: 

z

The throttle position (TP)  

z

The barometric pressure (BARO)  

z

The intake air temperature (IAT)  

z

The engine RPM  

The PCM compares the predicted MAF value to the actual MAF value, and to the speed density calculation, in 
order to verify the proper throttle operation. 

Conditions for Running the DTC 

z

DTCs P0601, P0602, P0604, P0606, P1516, P2101, P2108, U0107 are not set.  

z

DTCs P0120 and P0220 are not active at the same time. 

or  

z

The engine operates longer than 1 second.  

z

The engine speed is more than 500 RPM.  

Conditions for Setting the DTC 

z

The PCM detects that the difference between the actual air flow and the speed density calculated air flow 
is more than expected.  

z

The above condition is met for less than 1 second.  

Action Taken When the DTC Sets 

z

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

z

The control module records the operating conditions at the time the diagnostic fails. The control module 
stores this information in the Freeze Frame and/or the Failure Records.  

z

The control module commands the TAC system to operate in the Reduced Engine Power mode. 

 

2004 Hummer H2 

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

Hummer H2

  

 

2004 Hummer H2 

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

Hummer H2

  

z

A message center or an indicator displays Reduced Engine Power.  

z

Under certain conditions the control module commands the engine OFF.  

Conditions for Clearing the MIL/DTC 

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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.  

Diagnostic Aids 

z

Inspect the throttle blade for being broken, bent, or missing.  

z

Inspect the TP sensor for proper installation. A sensor that is mis-aligned could set this DTC.  

z

Inspect the throttle actuator control (TAC) module connectors for signs of water intrusion. If water 
intrusion occurs, multiple DTCs may set without any circuit or component conditions found during 
diagnostic testing.  

z

Physically and visually inspect the throttle body assembly and correct any problems that you observe. 
Manually move the throttle blade from closed to wide open throttle (WOT). You should not need to use 
excess force. The throttle blade should move smoothly through the full range, then should independently 
return to a slightly open position.  

z

When the TAC module detects a condition within the TAC system, more than one TAC system related 
DTC may set. This is due to the many redundant tests run continuously on this system. Locating and 
repairing one individual condition may correct more than one DTC. Disconnecting components during 
testing may set additional DTCs. Remember this if you review the stored information in Capture Info.  

z

For an intermittent condition, refer to Intermittent Conditions .  

Test Description 

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

5: This step will determine if the manifold absolute pressure (MAP) sensor voltage is within the proper 
range at idle.  

6: This step will determine if the MAP sensor responds properly to the change in manifold pressure.  

7: A throttle blade that sticks or binds may set this code. Opening the throttle through the entire range 
will indicate problems such as these.  

9: When the PCM detects a condition within the ETC system other DTCs may set due to the many 
redundant tests run continuously on this system. Locating and repairing one individual condition may 
correct more than one DTC. Keep this in mind when reviewing captured DTC info.  

DTC P0068 

 

2004 Hummer H2 

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

Hummer H2

  

Step

Action

Values

Yes

No

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

Are any other DTCs set?

-

Go to 

Diagnostic 

Trouble Code 

(DTC) List

Go to Step 3

3

1. Observe the Freeze Frame/Failure Records for 

this DTC.  

2. Turn OFF the ignition.  

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 Diagnostic 

Aids

4

Inspect for the following conditions: 

z

Vacuum hoses for splits, kinks, and proper 
connections as shown on Vehicle Emission 
Control Information label-Inspect thoroughly 
for any type of leak or restriction.  

z

Air leaks at throttle body mounting area and 
intake manifold sealing surfaces  

 
Did you find and correct the condition?

-

Go to Step 8

Go to Step 5

5

1. Allow the engine to reach operating 

temperature.  

2. Observe the MAP sensor voltage parameter 

with a scan tool.  

Is the manifold absolute pressure (MAP) sensor 
voltage within the specified range?

0.8-2.0 

V

Go to Step 6

Go to DTC P0106 

(With Throttle 

Actuator 

Control)

1. Idle the engine.  

2. Observe the MAP sensor kPa parameter with a 

scan tool.  

 

2004 Hummer H2 

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

Hummer H2

  

DTC P0101 (WITH THROTTLE ACTUATOR CONTROL) 

Circuit Description 

The mass air flow (MAF) sensor is an air flow meter that measures the amount of air entering the engine. The 
powertrain control module (PCM) uses the MAF sensor signal to provide the correct fuel delivery for all engine 

6

3. Increase the engine speed slowly and then 

back to idle.  

Does the MAP sensor kPa change smoothly and 
gradually as engine speed is increased and returned 
to idle?

-

Go to Step 7

Go to DTC P0106 

(With Throttle 

Actuator 

Control)

7

1. Inspect the throttle body for the following 

conditions while modulating the throttle 
through the entire range using the scan tool: 

z

Loose or damaged throttle blade  

z

Broken throttle shaft  

z

Drive mechanism damage  

2. If any of the above conditions exist, replace 

the throttle body assembly. Refer to Throttle 
Body Assembly Replacement .  

Did you find and correct the condition?

CAUTION:

Turn OFF the ignition before inserting 
fingers into the throttle bore. Unexpected 
movement of the throttle blade could cause 
personal injury.

-

Go to Step 6

Go to Diagnostic 

Aids

8

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.  

Did the DTC fail this ignition?

-

Go to Step 2

Go to Step 7

9

Observe the Capture Info with a scan tool. 
Are there any DTCs that have not been diagnosed?

-

Go to 

Diagnostic 

Trouble Code 

(DTC) List

System OK

 

2004 Hummer H2 

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

Hummer H2