Hummer H1 (2006+). Manual — part 134

OBD-380

On-Board Diagnostics

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Diagnostic Aids

• Inspect the wiring for poor electrical connections at the TCM. Inspect for the following conditions:

• A bent terminal

• A backed-out terminal

• A damaged terminal

• Poor terminal tension

• A chafed wire

• A broken wire inside the insulation

• When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a

change.

• You may have to drive the vehicle in order to experience a condition.

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to

Diagnostic

System Check

2

1.

Install the scan tool.

2.

Turn ON the ignition, with the engine OFF.

NOTE: Before clearing the DTC, use the scan tool in order to
record the Freeze Frame and Failure Records for reference. The
Clear Info function will erase the data.

3.

Record the DTC Freeze Frame and Failure Records.

4.

Clear the DTC.

NOTE: If other DTCs are present, refer to the applicable diag-
nostic tables before continuing.

5.

Using a DVOM, measure and record the voltage at the bat-
tery terminals.

Is voltage within the specified value?

B+

Go to Step 3

Go to Battery

Inspection

3

Start the engine and warm to normal operating temperature.

Is the Alternator/Check Engine lamp ON?

Go to Charging

System Test

Go to Step 4

4

1.

Increase the engine speed to 1,000-1,500 RPM.

2.

Observe the system voltage on the scan tool.

Is voltage within the specified range?

13-15

Volts

Go to Step 5

Go to Charging

System Test

5

1.

Turn the ignition OFF.

2.

Disconnect the TCM connector C78.

3.

Install the J 39700 breakout box and the J 43799 breakout
box adapter. Additional DTCs may set.

4.

Turn the ignition ON, with the engine OFF.

5.

Using a DVOM, measure the voltage between connector
C78 terminal 1 and terminal 2, with the ignition ON.

6.

Measure the voltage between connector C78 terminal 1 and
terminal 3, with the ignition OFF.

Is voltage within the specified value of B+ voltage?

0.5 Volts

Go to Step 6

Go to Step 7

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On-Board Diagnostics OBD-381

5745804

6

1.

Inspect the transmission wiring harness assembly.

2.

Repair the transmission wiring harness assembly.

Did you complete the repair?

Go to Step 8

7

NOTE: In most cases, the TCM is not at fault. Investigate thor-
oughly before replacing the TCM.

Replace the faulty TCM.

Did you complete the replacement?

Go to Step 8

8

Perform the following procedure in order to verify the repair:

1.

Clear the DTC.

2.

Using the scan tool, monitor system voltage.

3.

Select Specific DTC.

4.

Enter DTC P0880.

Has the test run and passed?

System OK

Go to Step 1

Step

Action

Value(s)

Yes

No

6-1-05

OBD-382

On-Board Diagnostics

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DTC P1093 Fuel Rail Pressure Low During Power Enrichment (Figure OBD-99)

Figure OBD-99: Fuel Rail Pressure Circuit

Circuit Description

The engine control module (ECM) uses the fuel rail pressure (FRP) sensor to determine fuel pressure to the fuel injectors. This is
then compared to the calculated target fuel pressure as determined by the ECM. The ECM adjusts the FRP by modulating the duty
cycle of the control driver of the fuel pressure regulator. Injector pulse duration is determined by the measured rail pressure and the
target injection fuel into each cylinder. If a sensor circuit malfunction is detected, or the commanded fuel injection pump flow is
not within the proper range for a given engine load and speed, DTCs will be set.

Conditions for Setting the DTC

The difference between the commanded fuel pressure and the actual fuel pressure is more than 20 MPa.

OR

The FRP regulator fuel flow is more than 19 mm

3

at 800 RPM, or more than 44 mm

3

at 2,000 RPM.

Action Taken When the DTC Sets

• The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.

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

tion in the Freeze Frame/Failure Records.

The engine will be in reduced power mode to replace using no more than 2,000 RPM.

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On-Board Diagnostics OBD-383

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.

Diagnostic Aids

• This DTC does not set for an idle condition.

• The following are some conditions that may cause DTC P0087 and DTC P1093 to set:

• Excessive fuel return to the tank

• A fuel injection pump failure

• A fuel pressure regulator (RPCV) failure

• If you have to prime the fuel system, inspect for the following conditions:

• A restricted fuel supply line

• A fuel supply line air leak--Refer to Fuel System Diagnosis .

• A sticking fuel pressure regulator may set this DTC. Refer to Fuel System Diagnosis - High Pressure Side . Perform this test

under the conditions for which the DTC set.

• If power enhancing devices have been attached to the fuel rail pressure sensor circuits, this DTC may set and adversely ef-

fect the fuel system components. Refer to Fuel System Diagnosis - High Pressure Side .

• If the condition is still intermittent, refer to Intermittent Conditions .

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to

Diagnostic

System Check

2

Is DTC P0168 or P0090 also set?

Go to DTC

P0168 or P0090

Go to Step 3

3

NOTE: Failure to wait until there is no engine control module
(ECM) communications with the scan tool will result in misdiag-
nosis.

1.

Turn OFF the ignition for 30 seconds.

2.

Turn ON the ignition, with the engine OFF.

3.

Observe the FRP Regulator Command parameter with a scan
tool.

Is the FRP Regulator Command more than the specified value?

20%

Go to Step 4

Go to Step 16

4

Attempt to start the engine.

Does the engine start and idle?

Go to Step 5

Go to Engine

Cranks but Does

Not Run

5

1.

Turn ON the ignition, with the engine OFF.

2.

Observe the Actual Fuel Rail Pressure parameter with a scan
tool.

3.

Is the Actual Fuel Rail Pressure Parameter within the speci-
fied range?

1-1.8 MPa

Go to Step 6

Go to Step 10