Hummer H1 (2006+). Manual - part 61

OBD-88

On-Board Diagnostics

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DTC P0112 Intake Air Temperature (IAT) Sensor Circuit Low Voltage (Figure OBD-26)

Figure OBD-26:   Intake Air Temperature (IAT) Sensor Circuit 

Circuit Description

The intake air temperature (IAT) sensor is a variable resistor. The IAT sensor has a signal circuit and a low reference circuit. The
IAT sensor measures the temperature of the air entering the engine. The engine control module (ECM) supplies 5 volts to the IAT
signal circuit, and a ground for the IAT low reference circuit. When the IAT sensor is cold, the sensor resistance is high. When the
air temperature increases, the sensor resistance decreases. With high sensor resistance, the ECM detects a high voltage on the IAT
signal circuit. With lower sensor resistance, the ECM detects a lower voltage on the IAT signal circuit. If the ECM detects an ex-
cessively low IAT signal voltage, indicating a high temperature, DTC P0112 sets. 

Conditions for Setting the DTC

The IAT 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 IAT
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. 

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 On-Board Diagnostics  OBD-89

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

Observe the IAT Sensor parameter with a scan tool.

Is the IAT 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 mass air flow (MAF)/intake air temperature 
(IAT) sensor. 

2.

Observe the IAT Sensor parameter with a scan tool.

Is the IAT Sensor parameter less than the specified value?

-39°C       

(-38°F)

Go to Step 6

Go to Step 5

    5

Test the IAT signal circuit 653 (YL) for the following conditions: 

• A short to ground 

• A short to the IAT low reference circuit 250 (BK)

• A short to the MAF sensor low reference circuit 251 (BK) 

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 MAF/
IAT 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 MAF/IAT sensor. 

Did you complete the replacement?

Go to Step 10

    9

Replace the faulty ECM. 

Did you complete the replacement?

Go to Step 10 

OBD-90

On-Board Diagnostics

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   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

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 On-Board Diagnostics  OBD-91

5745804

DTC P0113 Intake Air Temperature Sensor (IAT) Sensor Circuit High Voltage (Figure OBD-27)

Figure OBD-27:   Intake Air Temperature (IAT) Sensor Circuit

Circuit Description

The intake air temperature (IAT) sensor is a variable resistor. The IAT sensor has a signal circuit and a low reference circuit. The
IAT sensor measures the temperature of the air entering the engine. The engine control module (ECM) supplies 5 volts to the IAT
signal circuit, and a ground for the IAT low reference circuit. When the IAT sensor is cold, the sensor resistance is high. When the
air temperature increases, the sensor resistance decreases. With high sensor resistance, the ECM detects a high voltage on the IAT
signal circuit. With lower sensor resistance, the ECM detects a lower voltage on the IAT signal circuit. If the ECM detects an ex-
cessively high IAT signal voltage, indicating a low temperature, DTC P0113 sets.

Conditions for Setting the DTC

The IAT Sensor parameter is less than -39°C (-38°F) for more than 10 seconds. This is equal to more than 4.86 volts on the IAT
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.