Hummer H1 (2006+). Manual - part 62

OBD-92

On-Board Diagnostics

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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

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.

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 4

Go to Step 3

Observe the Freeze Frame/Failure Records for this DTC.
Turn OFF the ignition for 60 seconds.

Start the engine.

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

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

Measure the voltage from the signal circuit 653 (YL) of the
IAT sensor 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

NOTE: If a short to B+ voltage occurs the sensor may be dam-
aged.

Test the IAT signal circuit 653 (YL) for a short to voltage.

Did you find and correct the condition?

Go to Step 15

Go to Step 12

Connect a 3-amp fused jumper wire between the signal circuit
653 (YL) of the IAT sensor and the low reference circuit 250
(BK) of the IAT sensor.

Is the IAT Sensor parameter more than the specified value?

148°C

(298°F)

Go to Step 10

Go to Step 7

Connect a 3-amp fused jumper wire between the signal circuit
653 (YL) of the IAT sensor and a good ground.

Is the IAT Sensor parameter more than the specified value?

148°C

(298°F)

Go to Step 9

Go to Step 8

Test the IAT signal circuit 653 YL) for an open circuit or for high
resistance Between C77 pin 24 and pin 2 of the IAT sensor con-
nector.

Did you find and correct the condition?

Go to Step 15

Go to Step 12

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On-Board Diagnostics OBD-93

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Test the IAT low reference circuit 250 (BK) for an open circuit or
for high resistance between C76 pin 58 and pin 1 of the IAT sen-
sor connector.

Did you find and correct the condition?

Go to Step 15

Go to Step 12

Test the IAT signal circuit 650 (YL) for a short to any 5-volt ref-
erence circuit.

Did you find and correct the condition?

Go to Step 15

Go to Step 11

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

Did you find and correct the condition?

Go to Step 15

Go to Step 13

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 15

Go to Step 14

Replace the faulty MAF/IAT sensor.

Did you complete the replacement?

Go to Step 15

Replace the faulty ECM.

Did you complete the replacement?

Go to Step 15

Clear the DTCs with a scan tool.

Turn OFF the ignition for 30 seconds.

Start the engine.

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 16

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

OBD-94

On-Board Diagnostics

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DTC P0116 Engine Coolant Rationality (Figure OBD-28)

Figure OBD-28: Coolant Temperature/Mass Air Flow and Air Intake Temperature Sensor Circuits

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 signal circuit and a ground for the low reference circuit. When the engine coolant
temperatures are low, the resistance is high. When the engine coolant temperatures are high the resistance is low. The ECM uses
this high side coolant rationality test to determine if the ECT input is skewed high. The ECM will record the amount of time the en-
gine is OFF. At restart the ECM will compare the temperature difference between the ECT and intake air temperature (IAT). Be-
fore failing this diagnostic, the ECM will perform the calculation to determine the presence of a block heater. If the temperature
difference is not within the calculated range, after the predetermined engine OFF time, DTC P0116 sets.

Conditions for Setting the DTC

If the ECM detects a start-up temperature difference between the ECT sensor and the IAT sensor of more than 5°C (9°F), then the
vehicle must be driven for more than 400 seconds over 24 km/h (15 mph) and the engine speed must be more than 600 RPM. If the
IAT sensor temperature decreases more than 5°C (9°F) then a block heater is detected and the test is aborted. If the IAT sensor tem-
perature does not decrease, then a block heater was not detected and DTC P0116 sets.

Action Taken When the DTC Sets

The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic
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 consecutive ignition cycle,

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On-Board Diagnostics OBD-95

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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

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.

Inspect the cooling system coolant level.

Is the cooling system coolant low?

Fill The Cooling

System

Go to Step 3

Observe and record the ambient air temperature of the vehicle en-
vironment using an accurate thermometer.

Did you complete the action?

Go to Step 4

NOTE: The engine needs to have been OFF for at least 10 hours
for the engine coolant temperature (ECT) and the intake air tem-
perature (IAT) to be at ambient temperature. The vehicle should
not have changed environments during this time.

Has the engine been OFF for the specified amount of time?

10 hrs

Go to Step 7

Go to Step 5

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

Remove the ECT sensor.

Place the sensors on a work surface away from any heat
source.

Allow the sensors to reach the ambient air temperature for
30-60 minutes.

Are the sensors at the ambient temperature?

Go to Step 6

Connect the MAF/IAT sensor to the electrical connector, but
DO NOT install it.

Insulate the sensor from any engine heat source.

Connect the ECT sensor to the electrical connector, but DO
NOT install it.

Insulate the sensor from any engine heat source.

Are the sensors connected?

Go to Step 7

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