Hummer H1 (2006+). Manual — part 138

OBD-396

On-Board Diagnostics

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DTC P1404 Exhaust Gas Recirculation (EGR) Closed Position Performance (Figure OBD-103)

Figure OBD-103: Exhaust Gas Recircuiation (EGR) Position Sensor

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. The ECM compares the actual EGR position with
the desired EGR position when the EGR valve is commanded open or closed. If the ECM detects a difference between the learned
closed position and the commanded closed position for a calibrated amount of time, DTC P1404 sets.

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On-Board Diagnostics OBD-397

5745804

Conditions for Setting the DTC

• The actual EGR position is 0.8 volts, 6 percent, more than the learned closed position when the EGR valve is commanded

closed, or the EGR learned minimum position is more than 1.25 volts.

• The above condition is present for more than 5 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 upda

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

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnos-

tic System

Check - Vehicle

2

NOTE: Attaching the shop exhaust system to the vehicle may
cause false exhaust gas recirculation (EGR) DTCs to set.

1.

Turn ON the ignition.

2.

Observe the EGR Position parameter with a scan tool.

Does the EGR Position parameter read more than the specified
value?

1.25 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

Go to Intermit-

tent Conditions

4

Is DTC P0403, P0405, or P0406 also set?

Go to DTC

P0403 or DTC
P0405 or DTC

P0406

Go to Step 5

5

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 6

OBD-398

On-Board Diagnostics

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6

1.

Disconnect the EGR valve.

2.

Turn ON the ignition.

3.

Set up the DVOM to measure amperage.

4.

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.

5.

Measure the amperage and note as Current Draw.

6.

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.

7.

Connect a DVOM in parallel between the low reference cir-
cuit 107 (BK) of the EGR position sensor and a good ground.

8.

Measure the voltage and note as Low Reference Voltage
Drop.

9.

Divide the Low Reference Voltage Drop by the Current Draw
in order to calculate the resistance in the low reference cir-
cuit.

Is the calculated resistance more than the specified value?

5 ohms

Go to Step 7

Go to Step 9

7

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 8

8

1.

Disconnect C76 to the ECM.

2.

Repair the high resistance in the low reference circuit 107
(BK).

Did you find and correct the condition?

Go to Step 12

Go to Step 11

9

1.

Remove the EGR valve.

2.

Inspect for debris and damage that will cause the EGR valve
to stick and clean, if necessary.

Did you find and correct the condition?

Go to Step 12

Go to Step 10

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

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

Go to Diagnos-

tic Trouble

Code (DTC)

List

System OK

Step

Action

Value(s)

Yes

No

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On-Board Diagnostics OBD-399

5745804

DTC P1550 Fuel Injector Control Module (FICM) System Voltage (Figure OBD-104)

Figure OBD-104: Fuel Injector Control Module (FICM) System Circuit