Hummer H1 (2006+). Instruction - page 65

OBD-104

On-Board Diagnostics

_____________________________________________

7

1.

Connect a 3-amp fused jumper between the signal circuit 623
(YL) of the ECT sensor and a good ground.

2.

Observe the ECT sensor parameter with a scan tool.

Is the ECT sensor parameter more than the specified value?

148°C

(298°F)

Go to Step 9

Go to Step 8

8

Test the signal circuit 623 (YL) of the ECT sensor for a high re-
sistance or an open between C76 pin 67 and pin B of the ECT
sensor connector.

Did you find and correct the condition?

Go to Step 15

Go to Step 12

9

Test the low reference circuit 624 (GY) of the ECT sensor for a
high resistance or an open between C76 pin 14 and pin A of the
ECT sensor connector.

Did you find and correct the condition?

Go to Step 15

Go to Step 12

10

Test the ECT signal circuit 623 (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

11

Test for an intermittent and for a poor connection at the ECT sen-
sor.

Did you find and correct the condition?

Go to Step 15

Go to Step 13

12

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

13

Replace the faulty ECT sensor.

Did you complete the replacement?

Go to Step 15

14

Replace the faulty ECM.

Did you complete the replacement?

Go to Step 15

15

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 16

16

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-105

5745804

DTC P0168 Fuel Temperature Sensor Over Temp (Figure OBD-31)

Figure OBD-31: Fuel Temperature Sensor Circuit

Circuit Description

The fuel temperature sensor is a thermistor type sensor. The engine control module (ECM) supplies 5 volts and a ground circuit to
the sensor. When the ECM detects a fuel temperature sensor above a pre-determined value, a type D code, no malfunction indicator
lamp (MIL) sets. A fuel cooler located in the cool pack is used to help keep the fuel temperature at an acceptable limit.

Conditions for Setting the DTC

The fuel temperature sensor is above 122°C (252°F) for more than 5 seconds.

Action Taken When the DTC Sets

• The control module stores the DTC information into memory when the diagnostic runs and fails.

• The malfunction indicator lamp (MIL) will not illuminate.

• The control module records the operating conditions at the time the diagnostic fails. The control module stores this informa-

tion in the Failure Records.

• The driver information center, if equipped, may display a message.

Conditions for Clearing the DTC

• 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 non-emission re-

lated diagnostic.

• Clear the DTC with a scan tool.

OBD-106

On-Board Diagnostics

_____________________________________________

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.

Inspect the fuel cooler located in the cool pack for debris
restricting the airflow or damage to the cooling fins.

2.

Inspect the fuel lines for kinks or damage.

3.

Clean or replace the above listed components as necessary.

Did any of the components require a repair?

Go to Step 11

Go to Step 3

3

1.

Disconnect the air filter outlet duct to access the fuel temper-
ature sensor.

2.

Disconnect the fuel temperature sensor electrical connector.

3.

Turn ON the ignition.

4.

Probe the fuel temperature sensor signal circuit 324 (YL)
with a DVOM connected to ground.

Is the voltage near the specified value?

5 V

Go to Step 4

Go to Step 5

4

1.

Connect a test lamp to B+.

2.

Probe the low reference circuit 252 (BR) of the fuel tempera-
ture sensor connector.

Does the test lamp illuminate?

Go to Step 7

Go to Step 6

5

1.

Turn OFF the ignition.

2.

Disconnect the engine control module (ECM) connector 76
that contains the fuel temperature sensor signal circuit.

3.

Inspect the signal circuit 324 (YL) for an open or short to
voltage or ground between C76 pin 27 and pin B of the FTS.

Did you find and correct the condition?

Go to Step 11

Go to Step 8

6

1.

Turn OFF the ignition.

2.

Disconnect the ECM connector 77 that contains the fuel tem-
perature sensor low reference circuit 252 (BR).

3.

Inspect the fuel temperature sensor low reference circuit
252(BR) and connectors for an open or high resistance
between C77 pin 48 and pin A of the FTS.

Did you complete the repair?

Go to Step 11

7

Inspect for poor connections at the fuel temperature sensor and
repair as necessary.

Did you find and correct the condition?

Go to Step 11

Go to Step 9

8

Inspect for poor connections at the ECM and repair as necessary.
Did you find and correct the condition?

Go to Step 11

Go to Step 10

9

Replace the faulty fuel temperature sensor.

Did you complete the replacement?

Go to Step 11

10

Replace the faulty ECM.

Did you complete the replacement?

Go to Step 11

_____________________________________________

On-Board Diagnostics OBD-107

5745804

11

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 12

12

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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