Hummer H1 (2006+). Manual - part 83

OBD-176

On-Board Diagnostics

_____________________________________________

    9

Test for shorted terminals and poor connections at the engine
control module (ECM). 

Did you find and correct the condition?

Go to Step 12

Go to Step 11

    10

Replace the faulty EGR valve. 

Did you complete the replacement?

Go to Step 12 

    11

Replace the faulty ECM. 

Did you complete the replacement?

Go to Step 12 

    12

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 13

   13

1.

Using the Scan Tool select “Capture Info,” Review Info.” Are 
any DTC’s displayed that have not been diagnosed?

Go to the appli-

cable DTC 

table.

System OK.

Step

Action

Value(s)

Yes

No

_____________________________________________

 On-Board Diagnostics  OBD-177

5745804

DTC P0406 Exhaust Gas Recirculation (EGR) Position Sensor Circuit High Voltage (Figure 
OBD-51)

Figure OBD-51:   Exhaust Gas Recirculation (EGR) Position Sensor Circuit

Circuit Description

The engine control module (ECM) uses the exhaust gas recirculation (EGR) position sensor to determine the position of the EGR
valve. The ECM sends a reference voltage through the 5-volt reference circuit to the EGR position sensor. The ECM provides a
voltage return path for the sensor through the low reference circuit. A variable voltage signal, based on the EGR valve position, is
sent from the sensor to the ECM through the EGR position sensor signal circuit. If the ECM detects an EGR position sensor volt-
age that is more than the normal operating range, DTC P0406 sets.

Conditions for Setting the DTC 

• The EGR position sensor voltage is more than 4.75 volts. 

• The above condition is present for more than 10 seconds. 

Action Taken When the DTC Sets - California 

• 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. 

OBD-178

On-Board Diagnostics

_____________________________________________

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

1.

Turn ON the ignition.

2.

Observe the EGR Position Sensor parameter.

Is the voltage more than the specified value?

4.75 Volts

Go to Step 4

Go to Step 3 

    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 cycle?

Go to Step 4 

 Intermittent Go 

to Diagnostic 

Aids

    4

Test for shorted terminals and poor connections at the exhaust
gas recirculation (EGR) valve. 

Did you find and correct the condition?

Go to Step 12 

Go to Step 5 

    5

1.

Disconnect the EGR valve.

2.

Observe the EGR Position parameter on the scan tool.

Is the voltage more than the specified value.

0 Volts

Go to Step 8 

Go to Step 6 

    6

Measure the voltage between the 5-volt reference circuit 106
(GY) of the EGR valve and the low reference circuit 107(BK) of
the EGR valve with a DVOM.

Is the voltage less than the specified value.

5 Volts

Go to Step 7 

Go to Step 10 

    7

Repair the open in the low reference circuit 107 (BK) of the EGR
valve.

Did you find and correct the condition?

Go to Step 12 

Go to Step 9 

    8

Repair the short to voltage in the signal circuit 105 (BR) of the
EGR valve. 

Did you complete the repair?

Go to Step 12 

Go to Step 9 

    9

Test for shorted terminals and poor connections at the engine
control module (ECM).

Did you find and correct the condition?

Go to Step 12

Go to Step 11 

_____________________________________________

 On-Board Diagnostics  OBD-179

5745804

    10

Replace the faulty EGR valve. 

Did you complete the replacement?

Go to Step 12 

    11

Replace the faulty ECM. 

Did you complete the replacement?

Go to Step 12 

    12

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 13

   13

1.

Using the Scan Tool select “Capture Info,” Review Info.” Are 
any DTC’s displayed that have not been diagnosed?

Go to the appli-

cable DTC 

table.

System OK.

Step

Action

Value(s)

Yes

No