Hummer H1 (2006+). Manual — part 80

OBD-164

On-Board Diagnostics

_____________________________________________

The wait to start indicator illuminates only with the ignition ON and the engine OFF. The wait to start indicator will not illuminate
during post-start glow plug operation.

The wait to start indicator will not stay ON for long at higher engine temperatures.

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

Turn the ignition ON, with the engine OFF.

Does the wait to start indicator illuminate and then turn OFF?

Intermittent Go

To Diagnostic

Aids

Go to Step 3

3

1.

Turn the ignition OFF.

2.

Disconnect the engine control module (ECM) connector 76.

3.

Turn the ignition ON, with the engine OFF.

4.

Measure the voltage from the wait to start signal circuit 338
(DB) of the ECM to a good ground.

Does the voltage measure greater than the specified value?

9.5 Volts

Go to Step 4

Go to Step 6

4

Test the wait to start signal circuit 338 (DB) for a short to volt-
age.

Did you find and correct the condition?

Go to Step 8

Go to Step 5

5

Inspect for poor connections at the harness connector of the
ECM.

Did you find and correct the condition?

Go to Step 8

Go to Step 7

6

Repair the short to ground in the wait to start signal circuit 338
(DB.

Did you complete the repair?

Go to Step 8

7

Replace the faulty ECM.

Did you complete the replacement?

Go to Step 8

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 9

9

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.

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On-Board Diagnostics OBD-165

5745804

DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient

Circuit Description

The engine control module (ECM) tests the exhaust gas recirculation (EGR) flow once per ignition cycle. When the proper en-
abling conditions are met, the ECM will close the EGR valve and then open the EGR valve while monitoring the mass air flow
(MAF) signal. An expected MAF difference should be detected between the open and closed positions. If the ECM does not see the
expected MAF difference, DTC P0401 sets.

Conditions for Setting the DTC

The MAF difference monitored by the ECM during the EGR flow test indicates an insufficient amount of EGR flow for 10 sec-
onds.

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.

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.

Observe the Freeze Frame/Failure Records for this DTC.

2.

Turn OFF the ignition for 30 seconds.

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

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 3

Go to Intermit-

tent Conditions

3

Is DTC P0101 also set?

Go to Step 8

Go to Step 4

OBD-166

On-Board Diagnostics

_____________________________________________

4

Is DTC P0404 or P1404 also set?

Go to P0404

P1404

Go to Step 5

5

Is DTC P0403, P0405, or P0406 also set?

Go to P0403

P0405 P0406

Go to Step 6

6

Inspect for engine vacuum leaks.

Did you find and correct the condition?

Go to Step 9

Go to Step 7

7

Inspect the exhaust system for leaks, for restrictions, and for a
modification of the original equipment manufacture (OEM) parts.

Did you find and correct the condition?

Go to Step 9

Go to Step 8

8

1.

Remove the exhaust gas recirculation (EGR) valve.

2.

Inspect for the following conditions:

• A stuck open EGR valve

• Leaks in the EGR valve and EGR passages

• Restrictions in the EGR valve and EGR passages

• Debris or damage that can cause the EGR valve to stick

partially open or partially closed If the EGR valve is
sticking or damaged and can not be cleaned, replace
the EGR valve.

Did you complete the repair?

Go to Step 9

9

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 10

10

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-167

5745804

DTC P0403 Exhaust Gas Recirculation (EGR) Solenoid Control Circuit (Figure OBD-48)

Figure OBD-48: Exhaust Gas Recirculation (EGR) Solenoid Control Circuit

Circuit Description

The exhaust gas recirculation (EGR) valve is controlled by the engine control module (ECM) through the EGR motor high control
and the EGR motor low control circuits. The ECM supplies voltage that is near ignition voltage to the high and low control circuits
at all times. The ECM will pulse width modulation (PWM) the low control circuit to ground when EGR is desired. The lower the
pulse width, the more the valve will open. The ECM will PWM the high control circuit to ground when the EGR valve is desired
closed. If the ECM detects an electrical malfunction on the control circuits, DTC P0403 will set.

Conditions for Setting the DTC

• The ECM detects an electrical malfunction on an EGR motor control circuit.

• 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.