Hummer H1 (2006+). Manual - part 64

 

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Hummer H1 (2006+). Manual - part 64

 

 

OBD-100

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

Observe the ECT Sensor parameter.

Is the ECT Sensor parameter more than the specified value?

148°C

(298°F)

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 60 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 4 

Intermittent Go 

to Diagnostic 

Aids

    4

1.

Disconnect the engine coolant temperature (ECT) sensor.

2.

Observe the ECT Sensor parameter with a scan tool.

Is the ECT Sensor parameter less than the specified value?

-39°C       

(-38°F)

Go to Step 6 

Go to Step 5 

    5

Test the ECT signal circuit 623 (YL) for a short to ground or for a
short to any low reference circuit. 

Did you find and correct the condition?

Go to Step 10

Go to Step 7 

    6

Test for shorted terminals and for poor connections at the ECT
sensor.

Did you find and correct the condition?

Go to Step 10

Go to Step 8 

    7

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

Did you find and correct the condition?

Go to Step 10

Go to Step 9

    8

Replace the faulty ECT sensor. 

Did you complete the replacement?

Go to Step 10 

    9

Replace the faulty ECM. 

Did you complete the replacement?

Go to Step 10 

_____________________________________________

 On-Board Diagnostics  OBD-101

5745804

   10

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 11 

   11

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-102

On-Board Diagnostics

_____________________________________________

DTC P0118 Engine Coolant Temperature (ECT) Sensor Circuit High Voltage (Figure OBD-30)

Figure OBD-30:   Engine Coolant Temperature (ECT) Sensor Circuit

Circuit Description

The engine coolant temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. The engine
control module (ECM) supplies 5 volts to the ECT signal circuit and a ground for the ECT low reference circuit. When the ECT is
cold, the sensor resistance is high. When the ECT increases, the sensor resistance decreases. With high sensor resistance, the ECM
detects a high voltage on the ECT signal circuit. With lower sensor resistance, the ECM detects a lower voltage on the ECT signal
circuit. If the ECM detects an excessively high ECT signal voltage, which is a low temperature indication, DTC P0118 sets.

Conditions for Setting the DTC

The ECT sensor temperature is less than -39°C (-38°F) for more than 10 seconds. This is equal to more than 4.76 volts on the ECT
signal circuit as measured by the ECM.

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 updates the Failure Records. 

_____________________________________________

 On-Board Diagnostics  OBD-103

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. 

Diagnostic Aids 

• If a short to a separate 5-volt source occurs, this DTC will set. 

• A skewed sensor could result in poor driveability conditions. Refer to Temperature vs Resistance. 

• After starting the engine, the ECT should rise steadily, then stabilize when the thermostat opens. 

• If the condition is suspected of being intermittent, refer to Intermittent Conditions and Inducing Intermittent Fault Condi-

tions in Wiring Systems. 

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

Observe the ECT Sensor parameter.

Is the ECT Sensor parameter more than the specified value?

148°C

(298°F)

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 60 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 4 

Intermittent Go 

to Diagnostic 

Aids

    4

1.

Disconnect the engine coolant temperature (ECT) sensor. 

2.

Measure the voltage from the signal circuit of the ECT sen-
sor to a good ground with a DVOM. 

Is the voltage more than the specified value?

5.2 Volts

Go to Step 5 

Go to Step 6 

    5

NOTE: If a short to B+ voltage occurs, the ECT sensor may be
damaged.

Test the ECT signal circuit for a short to voltage.

Did you find and correct the condition?

Go to Step 15 

Go to Step 12 

    6

1.

Connect a 3-amp fused jumper between the signal circuit 623 
(YL) of the ECT sensor and the low reference circuit 624 
(GY).

2.

Observe the ECT sensor parameter with the scan tool.

Is the ECT sensor parameter more than the specified value?

148°C

(298°F)

Go to Step 10 

Go to Step 7 

 

 

 

 

 

 

 

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