Hummer H1 (2006+). Manual - part 82

OBD-172

On-Board Diagnostics

_____________________________________________

    6

NOTE: Failure to perform the following procedure can result in
inaccurate test results.

NOTE: Direct battery voltage to the EGR valve motor is not to
exceed 5 seconds.

1.

Disconnect the EGR valve.

2.

Start the engine.

3.

Measure the ignition voltage at the battery and note as supply 
voltage.

4.

Connect a 5-amp fused jumper between the battery positive 
terminal and the high control circuits 108/110 (OR/BK) ter-
minal on the EGR valve.

5.

Set up the DVOM to measure amperage.

6.

Connect a DVOM between the battery negative terminal and 
the low control circuits 109/111 (LG/BK) terminal on the 
EGR valve.

7.

Measure the amperage and note as current draw.

8.

Remove the DVOM and the 5-amp fused jumper wire.

9.

Divide the supply voltage by the current draw in order to cal-
culate the resistance of the EGR valve motor coil.

Is the calculated resistance within the specified value for the
specified EGR coil case temperature?

-40°C (-

40°F)

1.42-2.88

ohms

25°C

(77°F)

1.62-3.28

ohms

90°C

(194°F)

1.75-3.66

ohms

150°C

(302°F)

1.89-4.05

ohms

Go to Step 7

Go to Step 14

    7

1.

Measure the voltage from the 5-volt reference circuit 106 
(GY) of the EGR position sensor to a good ground with a 
DVOM and note as "supply voltage."

2.

Connect a test lamp and a DVOM in series between the 5-
volt reference circuit 106 (GY) of the EGR position sensor 
and the low reference circuit 107 (BK) of the EGR position 
sensor.

3.

Measure the amperage and note as "current draw."

4.

Remove the DVOM and connect the test lamp between the 5-
volt reference circuit 106 (GY) of the EGR position sensor 
and the low reference circuit 107 (BK) of the EGR position 
sensor.

5.

Connect a DVOM in parallel between the 5-volt reference 
circuit 106 (GY) of the EGR position sensor and a good 
ground.

6.

Measure the voltage and note as "load voltage drop."

7.

Subtract the "load voltage drop" from the "supply voltage" 
and divide your answer by the "current draw" in order to cal-
culate the resistance in the 5-volt reference circuit 106 (GY).

Is the calculated resistance more than the specified value?

300 ohms

Go to Step 10

Go to Step 8

    8

1.

With the test lamp still connected, connect a DVOM in paral-
lel between the low reference circuit 107 (BK) of the EGR 
position sensor and a good ground.

2.

Measure and note the "low reference voltage drop."

3.

Divide the "low reference voltage drop" by the "current 
draw" measured in the previous step in order to calculate the 
resistance in the low reference circuit 107 (BK).

Is the calculated resistance more than the specified value?

5 ohms

Go to Step 10

Go to Step 9

Step

Action

Value(s)

Yes

No

_____________________________________________

 On-Board Diagnostics  OBD-173

5745804

    9

1.

Remove the test lamp and the DVOM.

2.

Connect a jumper wire between the 5-volt reference circuit 
106 (GY) of the EGR position sensor and the signal circuit 
105 (BR/WH) of the EGR position sensor.

3.

Observe the EGR Sensor parameter with a scan tool.

Is the voltage more than the specified value?

4.9 Volts

Go to Step 11

Go to Step 10

    10

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

Did you find and correct the condition?

Go to Step 16

Go to Step 12

    11

1.

Turn OFF the ignition.

2.

Disconnect the ECM.

3.

Test the EGR motor high control circuits 108/110 OR/BK) 
and low control circuits 109/111 (LG/BK) for high resis-
tance.

Is the resistance more than the specified value?

High Con-

trol Circuit 

= -7 ohms

Low Con-

trol Circuit 

= -9 ohms

Go to Step 12

Go to Step 13

    12

Repair the high resistance in the affected circuit. 

Did you find and correct the condition?

Go to Step 16

Go to Step 15

    13

1.

Remove the EGR valve. 

2.

Inspect for debris that will cause the EGR valve to stick. 
Clean if necessary. 

Did you find and correct the condition?

Go to Step 16

Go to Step 14

    14

Replace the faulty EGR valve. 

Did you complete the replacement?

Go to Step 16

    15

Replace the faulty ECM. 

Did you complete the replacement?

Go to Step 16

    16

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 17

   17

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

OBD-174

On-Board Diagnostics

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DTC P0405 Exhaust Gas Recirculation (EGR) Position Sensor Circuit Low Voltage (Figure 
OBD-50)

Figure OBD-50:   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 less than the normal operating range, DTC P0405 sets.

Conditions for Setting the DTC 

• The EGR position sensor voltage is less than 0.25 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. 

_____________________________________________

 On-Board Diagnostics  OBD-175

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

1.

Turn ON the ignition.

2.

Observe the EGR Position Sensor parameter.

Is the voltage less than the specified value?

0.26 V

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

Go To Intermit-

tent Conditions 

    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.

Turn ON the ignition.

3.

Measure the voltage from the 5-volt reference circuit 106 
(GY) of the EGR valve to a good ground with a DVOM.

Is the voltage less than the specified value?

5 Volts

Go to Step 7

Go to Step 6

    6

1.

Connect a jumper wire between the 5-volt reference circuit 
106 (CY) of the EGR valve and the signal circuit of the EGR 
valve.

2.

Observe the EGR Position Sensor parameter with a scan 
tool.

Is the voltage less than the specified value?

5 Volts

Go to Step 8

Go to Step 10

    7

Repair the open or high resistance in the 5-volt reference circuit
106 (GY) of the EGR valve. 

Did you find and correct the condition?

Go to Step 12 

Go to Step 9

    8

Repair the open or short to ground in the signal circuit 105 (BR/
WH) of the EGR valve. 

Did you complete the repair?

Go to Step 12

Go to Step 9