Hummer H1 (2006+). Manual - part 63

OBD-96

On-Board Diagnostics

_______________________________________________

    7

NOTE: The IAT sensor will start to warm-up as soon as the igni-
tion is turned ON.

1.

Turn ON the ignition.

2.

Take a snapshot of the Engine Data List with a scan tool. 
Review the snapshot data that was taken with the scan tool.
Observe the ECT Sensor parameter with a scan tool.

3.

Observe the IAT Sensor parameter with a scan tool.

Is the difference between the ECT Sensor parameter and the IAT
Sensor parameter more than the specified value?

5°C (9°F)

Go to Step 8 

 Intermittent Go 

To Diagnostic 

Aids

    8

Observe the recorded IAT Sensor parameter.

Is the difference between the IAT Sensor parameter and the am-
bient air temperature less than the specified value?

5°C (9°F)

Go to Step 9 

Go to Step 10 

    9

Observe the recorded ECT Sensor parameter.

Is the difference between the ECT Sensor parameter and the am-
bient air temperature less than the specified value?

5°C (9°F)

Intermittent Go 

To Diagnostic 

Aids

Go to Step 12 

    10

1.Disconnect the MAF/IAT sensor.

2.Test for an intermittent and for a poor connection at the IAT
sensor.

Did you find and correct the condition?

Go to Step 24 

Go to Step 11

    11

1.

At the sensor, measure the resistance between the IAT signal 
pin 2 and pin 1 the IAT low reference terminals with a 
DVOM and record the value. 

2.

Compare the resistance measurement of the IAT sensor to the 
ambient air temperature using the Temperature vs. Resis-
tance table.

Is the resistance measurement of the IAT sensor within the speci-
fied range?

Go to Step 14

Go to Step 21

    12

1.

Disconnect the ECT sensor.

2.

Inspect for the following conditions:

• An ECT sensor leaking engine coolant internally through 

the sensor 

• Corrosion on the ECT sensor terminals 

• Corrosion on the ECT harness connector terminals 

Did you find and correct the condition?

Go to Step 23

Go to Step 13 

    13

NOTE: Do not hold the ECT sensor by the probe.

1.

At the sensor, measure the resistance between the ECT signal 
and the ECT low reference terminals with a DVOM and 
record the value. 

2.

Observe the recorded ambient air temperature.

3.

Compare the resistance measurement of the ECT sensor to 
the ambient air temperature using the Temperature vs. Resis-
tance table.

Is the resistance measurement of the ECT sensor within the spec-
ified range?

Go to Step 15 

Go to Step 22

Step

Action

Value(s)

Yes

No

______________________________________________

 On-Board Diagnostics  OBD-97

5745804

    14

Measure the voltage from the IAT signal circuit 653 (YL) to a
good ground with a DVOM.

Is the voltage within the specified range?

4.8-5.2

Volts

Go to Step 16

Go to Step 17

    15

Measure the voltage from the ECT signal circuit 623 (YL) to a
good ground with a DVOM. 

Is the voltage within the specified range?

4.8-5.2

Volts

Intermittent Go 

To Diagnostic 

Aids

Go to Step 19

    16

NOTE: All electrical components and accessories must be turned
OFF. Performing this step will disable the diagnostic for 10
hours.

1.

Turn OFF the ignition for 90 seconds to allow the control 
modules to power down.

2.

Measure the resistance from the low reference circuit 250 
(BK) of the IAT sensor to a good ground with a DVOM. 

Is the resistance less than the specified value?

5 ohms

Intermittent Go 

To Diagnostic 

Aids

Go to Step 18 

    17

Test the IAT signal circuit 653 (YL) for a high resistance be-
tween C77 pin 24 and pin 2 of the IAT sensor connector. 

Did you find and correct the condition?

Go to Step 24 

Go to Step 20 

    18

Test the IAT low reference circuit 250 (BK) for a high resistance
between C76 pin 58 and pin1 of the IAT sensor connector. 

Did you find and correct the condition?

Go to Step 24 

Go to Step 20 

    19

Test the ECT signal circuit 623 (YL) for a high resistance short to
ground between C76 pin 67 and pin B of the ECT sensor connec-
tor.

Did you find and correct the condition?

Go to Step 24

Go to Step 20 

    20

Test for an intermittent and for a poor connection at the engine
control module (ECM). 

Did you find and correct the condition?

Go to Step 24 

Go to Step 23

    21

Replace the faulty MAF/IAT sensor. 

Did you complete the replacement?

Go to Step 24

    22

Replace the faulty ECT sensor. 

Did you complete the replacement?

Go to Step 24

    23

Replace the faulty ECM. 

Did you complete the replacement?

Go to Step 24

    24

Reassemble the vehicle as necessary.

Did you complete the action?

Go to Step 25

Step

Action

Value(s)

Yes

No

OBD-98

On-Board Diagnostics

_______________________________________________

   25

NOTE: This DTC will not run without the engine being OFF for
at least 10 hours.

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 26 

   26

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-99

5745804

DTC P0117 Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage (Figure OBD-29)

Figure OBD-29:   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 low ECT signal voltage, which is a high temperature indication, DTC P0117 sets.

Conditions for Setting the DTC

The ECM detects that the ECT Sensor parameter is more than 148°C (298°F) for more than 10 seconds. This is equal to less than
0.24 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.