Hummer H1 (2002+). Manual - part 283

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PCM/Tech 1 Scan Tool 65

®

05745159

DTC P0228 - Accelerator Pedal Position (APP) Sensor 3 Circuit High Voltage

Step

Action

Value(s)

Yes

No

1

Important:

 Before clearing DTC(s) use the scan tool “Capture Info” to

record Freeze Frame and Failure Record for reference, as data will be lost
when “Clear Info” function is used.

Was the “On-Board Diagnostic (OBD) System Check” performed?

—

Go to Step 2.

Go to OBD

System Check.

2

1. Ignition “ON”, engine “OFF”.
2. With the throttle closed, observe APP 3 display on the scan tool.

Is APP 3 above the specified value?

4.75v

Go to Step 4. Go to Step 3.

3

DTC is intermittent. If no additional DTCs are stored, refer to “Diagnostic
Aids”. If additional DTCs were stored, refer to those chart(s).

Are additional DTCs stored? 

—

Go to the 

applicable 

DTC table.

Go to 

Diagnostic 

Aids.

4

1. Disconnect the APP sensor electrical connector.
2. Observe the APP 3 display on the Scan Tool.

Is APP 3 less than or equal to the specified value?

—

Go to Step 5. Go to Step 7.

5

Probe APP 3 sensor ground circuit at the APP sensor harness connector 
with a test light connected to B+.
Is the test light “ON”?

0.25v

Go to Step 8.

Go to Step 6.

6

1. Check for a short to voltage on the APP 3 sensor signal circuit.
2. If the APP 3 sensor signal circuit is shorted, repair it as necessary.
Was the APP 3 sensor signal circuit shorted?

—

Go to Step 11. Go to Step 10.

7

1. Check for an open sensor ground circuit.
2. If a problem is found, repair as necessary.

Was APP 3 sensor ground circuit open?

—

Go to Step 11. Go to Step 10.

8

Check for poor electrical connections at the APP sensor and replace termi-
nals if necessary.
Did any terminals require replacement?

—

Go to Step 11.

Go to Step 9.

9

Replace the APP module.

Is Action complete?

—

Go to Step 11.

—

10

Replace the faulty PCM. Notice: If the PCM is faulty, the new PCM must 
be programmed. Go to PCM replacement and programming procedures.
Is the action complete?

—

Go to Step 11.

—

11

1. Using the Scan Tool, select “DTC”, “Clear Info”.
2. Start engine and idle at normal operating temperature.

3. Select “DTC”, “Specific”, then enter the DTC number which was set.

4. Operate vehicle within the conditions for setting this DTC as specified in

the supporting text.

Does the Scan Tool indicate that this diagnostic Ran and Passed?

—

Go to Step 12.

Go to Step 2.

12

Using the Scan Tool, select “Capture Info”, “Review Info”.
Are any DTCs displayed that have not been diagnosed?

—

Go to the 

applicable 

DTC table

System OK

66

PCM/Tech 1 Scan Tool

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®

DTC P0231 Fuel Lift Pump Secondary Circuit 
Low Voltage

Circuit Description

The status of the lift pump is monitored by the PCM. This sig-
nal is also used to store a DTC if the fuel pump relay is defec-
tive or fuel pump voltage is lost while the engine is running.
There should be about 12 volts on circuit 120 during glow plug
cycle. This is a Type B DTC.

Conditions for Setting the DTC

• Fuel lift pump commanded “ON”.

• Ignition voltage minus 4 volts.

• Fuel lift pump voltage less than ignition voltage value.

• Conditions met for 2 seconds.

Action Taken When the DTC Sets

No action taken.

Conditions for Clearing the MIL/DTC

• The PCM will turn the MIL off after three consecutive 

trips without a fault condition.

• A History DTC will clear when forty consecutive 

warm-up cycles that the diagnostic does not fail (coolant 
temperature has risen 5°C (40°F) from start up coolant 
temperature and engine coolant temperature exceeds 
71°C (160°F) that same ignition cycle).

• Use of a Scan Tool

Diagnostic Aids

This DTC will not check the fuel pump operation.

Test Description

Number(s) below refer to the number(s) on the diagnostic ta-
ble.

3. This step will check the fuel pump circuit.

FUSE 2D
20A
INTERIOR

FUEL PUMP
RELAY
EXTERIOR
FUSE BOX

C1-10

G2

POWERTRAIN

CONTROL

MODULE

FUEL PUMP

RELAY CONTROL

FUEL LIFT
PUMP SIGNAL

TO FUEL

SELECTOR SWITCH

M

G2

FUEL
LIFT
PUMP

B

A

57 BK

787 GY

787 GY

787 GY

C27-D5

57 BK

C27-D8

238 DG

537 OR

9-S12-051

9-S12-051

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PCM/Tech 1 Scan Tool 67

®

05745159

DTC P0231 - Fuel Lift Pump Secondary Circuit Low Voltage

Step

Action

Value(s)

Yes

No

1

Important:

 Before clearing DTC(s) use the scan tool “Capture Info”.

Was the “On-Board Diagnostic (OBD) System Check” performed?

—

Go to Step 2. Go to OBD Sys-

tem Check.

2

1. Turn the ignition “OFF” for 20 seconds.
2. Turn the ignition “ON”.

3. Listen for the fuel lift pump.

Does the lift pump operate during glow plug cycle and then turn “OFF”?

—

Go to 

Diagnostic 

Aids.

Go to Step 3.

3

1. Turn the ignition “OFF”.
2. Probe the fuel pump test terminal with a fused jumper to “B+”.

Does the fuel pump operate?

—

Go to Step 8.

Go to Step 4.

4

1. Disconnect the fuel pump relay.
2. Probe the fuel pump test terminal with a fused jumper to “B+”.

Does the fuel pump operate?

—

Go to Step 5. Go to Step 6.

5

Replace the faulty fuel pump relay.
Is the action complete?

—

Go to Step 6.

—

6

Check for a an open fuel pump signal circuit.
Was a problem found?

—

Go to Step 7.

Go to Step 8.

7

Repair the open fuel pump signal circuit.
Is the action complete?

—

Go to Step 8.

—

8

1. Turn the ignition “OFF”.
2. Remove the fuel pump relay.

3. Connect a test light to ground.

4. Probe the fuel pump relay harness connector terminal number “B1”.

Is the test light “ON”?

—

Go to Step 10.

Go to Step 9.

9

Repair the open in the battery feed circuit to the fuel pump relay.
Is the action complete?

—

Go to Step 10.

—

10

Connect a test light between terminal number “B1” and terminal number 
“A1” of the fuel pump relay harness connector.
Is the test light “ON”?

—

Go to Step 12. Go to Step 11.

11

Repair the open fuel pump relay ground circuit.
Is the action complete?

—

Go to Step 12.

—

12

1. Turn the ignition “OFF”.
2. Connect a test light between terminal number “B3” and ground.

3. Monitor the test light.

4. Turn the ignition “ON”.

Was a problem found?

—

Go to Step 16. Go to Step 13.

13

Check for an open in circuit from fuel pump relay harness connector termi-
nal number “B3” and PCM.
Was a problem found?

—

Go to Step 14. Go to Step 15.

14

Repair the open in the fuel pump relay control circuit.
Is the action complete?

—

Go to Step 15.

—

15

Replace the faulty PCM. Notice: If the PCM is faulty, the new PCM must 
be programmed. Go to PCM replacement and programming procedures.
Is the action complete?

—

Go to Step 16.

—

16

Check for a faulty connection at fuel pump relay harness connector terminal 
number “B3”.
Was a problem found?

—

Go to Step 18. Go to Step 17.

17

Replace the faulty fuel pump relay.
Is the action complete?

—

Go to Step 18.

—

68

PCM/Tech 1 Scan Tool

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®

DTC P0236 Turbocharger (TC) Boost System

Circuit Description

The PCM operates a solenoid to control boost. This solenoid is
normally open. By providing a ground path the PCM energizes
the solenoid which then allows vacuum to pass to the waste-
gate valve. During normal operation, the PCM compares its
wastegate duty cycle signal with the boost signal and makes
corrections in the duty cycle accordingly. This is a type B
DTC.

Conditions for Setting the DTC

• Engine speed greater than 2400 RPM.
• Fuel rate greater than 20 mm.
• Boost pressure less than or equal to 20 kPa from desired 

(internal to PCM).

• Conditions met for 10 seconds.

or

• Engine speed greater than 1800 but less than 2400 RPM.
• Fuel rate greater than 20 mm.
• Boost pressure less than or equal to (110 kPa) - ((100 

kPa - Baro)/2) (internal to PCM).

• Conditions met for 2 seconds.

Action Taken When the DTC Sets

• Poor performance.
• Reduce maximum fuel.
• No TCC.

Conditions for Clearing the MIL/DTC

• The PCM will turn the MIL off after three consecutive 

trips without a fault condition.

• A History DTC will clear when forty consecutive 

warm-up cycles that the diagnostic does not fail (coolant 
temperature has risen 5°C (40°F) from start up coolant 
temperature and engine coolant temperature exceeds 
71°C (160°F) that same ignition cycle).

• Use of a Scan Tool.

Diagnostic Aids

A vacuum leak or a pinched vacuum line may cause a DTC
P0236. Check all vacuum lines and components connected to
the hoses for leaks or sharp bends. Check vacuum source. A
possible EGR DTC will store if there is a problem with the
vacuum source. Also check for proper vacuum line routing.
This diagnostic checks for a “skewed” sensor.

Test Description

Number(s) below refer to the number(s) on the diagnostic ta-
ble.

This will check the Boost sensor scaling. One step will check
the scaling with vacuum applied and one without.

5 VOLT

REFERNCE

CKP
SENSOR
SIGNAL

SENSOR

GROUND

CRANK
SHAFT
POSITION
SENSOR
(CKP)

A

B

B

A

B

B

A

A

C

C

C5-B12

C5-B5

C5-B9

BOOST/
BARO
PRESSURE
SENSOR

INTAKE AIR
TEMPERATURE
SENSOR (IAT)

ENGINE
COOLANT
TEMP
SENSOR
(ECT)

C5-B10

POWERTRAIN
CONTROL
MODULE

CKP

SENSOR

SIGNAL

SENSOR

GROUND

5 VOLT

REFERENCE

BOOST

SENSOR

SIGNAL

SENSOR

GROUND

ECT

SENSOR

SIGNAL

IAT

SENSOR

SIGNAL

C29-A5

359 BK

C5-C4

C5-C5

C27-C1

C27-D13

C27-C14

C29-B12

349 YL

651 PP

350 LG

394 LB

359 BK

C5-B11

TO
TFT
SENSOR

357 TN

354 YL

9-S12-066

FUSE 5C
10AMP
INTERIOR

FUSE 3A
10 AMP
EXTERIOR

ON/
OFF

SET
COAST

RESUME
ACCEL

HOT IN RUN
AND START

HOT IN RUN
AND START

A

29

42

37

C1

C29-A11

C29-B11

C27-D10

C28-D14

C28-C2

C27-D12

C27-D3

C27-D4

C27-D6

C29-B2

C29-B1

C27-C5

C29-A12

C5-D3

C5-A4

A

B

154 TN

151 GY

152 DB

153 LG

ON / OFF
SIGNAL

SET
COAST
SIGNAL

RESUME
ACCEL
SIGNAL

WASTEGATE
SOLENOID
CONTROL

5 VOLT
REFERENCE

APP 3
SIGNAL

GROUND

APP 1
SIGNAL

GROUND

GROUND

D

B

C

A

G

E

F

J

K

3

1

2

C1

22

20

14

15

60

32

53

17

44

720 TN

717 WH

723 YL

724 DG

725 GY

718 DB

719 BR

721 LB

722 PP

ACCELERATIOR
PEDAL POSITION
SENSOR

POWERTRAIN
CONTROL
MODULE
(PCM)

APP 2
SIGNAL

9-S12-055

B

C

D

295 BR

YL

GRN

RD