Hummer H1 (2006+). Manual - part 40

OBD-4

On-Board Diagnostics

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DTC P1093 Fuel Rail Pressure Low During Power Enrichment  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-381
DTC P1094 Fuel Rail Pressure Low During Idle or Decel Fuel Cut-Off (DFCO)   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-385
DTC P1123, P1226, P1229, P1232, P1235, P1238, P1241, P1244 Injector Output Circuit  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-391
DTC P1125 Accelerator Pedal Position (APP) System  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-388
DTC P1404 Exhaust Gas Recirculation (EGR) Closed Position Performance   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-395
DTC P1550 Fuel Injector Control Module (FICM) System Voltage  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-398
DTC P1621 Engine Control Module (ECM) Long Term Memory Performance  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-197
DTC P2122 Accelerator Pedal Position (APP) Sensor 1 Circuit Low Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-401
DTC P2123 Accelerator Pedal Position (APP) Sensor 1 Circuit High Voltage   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-405
DTC P2127 Accelerator Pedal Position (APP) Sensor 2 Circuit Low Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-409
DTC P2128 Accelerator Pedal Position (APP) Sensor 2 Circuit High Voltage   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-413
DTC P2132 Accelerator Pedal Position (APP) Sensor 3 Circuit Low Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-417
DTC P2133 Accelerator Pedal Position (APP) Sensor 3 Circuit High Voltage   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-421
DTC P2138 Accelerator Pedal Position (APP) Sensor 1-2 Correlation   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-425
DTC P2139 Accelerator Pedal Position (APP) Sensor 1-3 Correlation   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-430
DTC P2140 Accelerator Pedal Position (APP) Sensor 2-3 Correlation   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-434
DTC P2146 Injector Positive Voltage Control Circuit Group1   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-436
DTC P2149 Injector Positive Voltage Control Circuit Group 2  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-437
DTC P2227 Barometric Pressure (BARO) Sensor Performance   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-438
DTC P2228 Barometric Pressure (BARO) Sensor Circuit Low Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-443
DTC P2229 Barometric Pressure (BARO) Sensor Circuit High Voltage   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-447
DTC P2563 Turbocharger Boost Control Position Sensor Performance   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-450
DTC P2564 Turbocharger Boost Control Position Sensor Circuit Low Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-455
DTC P2565 Turbocharger Boost Control Position Sensor Circuit High Voltage  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-458
DTC P2610 Engine Control Module (ECM) Ignition Of Timer Performance   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-197
DTC P2636 Fuel Transfer Pump Flow Insufficient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-462
DTC P2771 Four Wheel Drive (4WD) Low Switch Circuit  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-466
DTC P2810 Solenoid G Electrical   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-468
DTC U0073 High Speed CAN Communication Bus  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-471
DTC U0100-U299 Lost Communication With Engine Control Module (ECM)  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-475

Engine Control Module (ECM)

Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-5
Replacement  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-5
Reprogramming   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-5
Schematics  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-35
Verifying Vehicle Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-5

Tech 2

Data List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-9
Diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-6
Information   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBD-6

ENGINE CONTROL MODULE (ECM)

The Engine Control Module (ECM) is located in the passenger compartment under the center console. It is the control center for
the fuel and emissions system. 

The ECM constantly looks at the information from various sensors, and controls the systems that affect vehicle performance.
Through periodic system checks the ECM can recognize operational problems and alert the driver through the Malfunction Indica-
tor Light (MIL). Problems are stored as Diagnostic Trouble Codes (DTCs), which identify the problem areas to aid the technician
in making repairs. 

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 On-Board Diagnostics  OBD-5

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The engine control Module, monitors a number of engine and vehicle functions and controls the following operations:

• Fuel control

• Fuel injection timing

• Speed Control

• Turbocharger Boost

• Transmission shift and shift quality functions. Specific transmission control diagnostics are covered in Section 5 of this ser-

vice manual.

ECM Repair

The only accepted repair to the ECM is replacement. 

If the diagnostic procedures call for the ECM to be replaced, it will be necessary to program the new ECM.

Important

• When replacing the production ECM with a service ECM, a DTC P1214 will be stored. It is important to program “TDC 

Offset” into the service ECM. Refer to “ECM Programming (TDC Offset).”

• When a ECM has been replaced, a short glow plug duration will exist during the first ignition cycle (less than 2 seconds). 

After the first ignition cycle, the glow plug system will operate properly.

• When replacing the production ECM with a service ECM, it is important to transfer the broadcast code and production ECM 

number to the service ECM label (do not record on ECM case). This will allow positive identification of ECM parts 
throughout the service life of the vehicle.

• To prevent internal ECM damage, the ignition must be “OFF” when disconnecting or reconnecting power to the ECM (for exam-

ple, battery cable, ECM pigtail, ECM fuse, etc.). The ignition should be “OFF” for at least 30 seconds before disconnecting 
power to the ECM.

ECM Replacement

Removal

1.

Allow 30 seconds to elapse, after the ignition is turned to the “off” position, before disconnecting the battery cables.

2.

Disconnect the negative battery cables.

3.

Gain access to the ECM from the center console.

4.

Unplug the connectors from the ECM.

5.

Remove the ECM mounting hardware and the ECM.

Installation

1.

Install the mounting hardware to the new ECM.

2.

Secure the connectors to ECM.

3.

Relocate the ECM in the center console and tighten hardware.

4.

Reconnect the negative battery cables.

NOTE: The MIL, and Check Throttle lamp will continue to be enabled until the ECM is programmed. Once the programming is
complete, the lamps will be turned “OFF” and normal operation will resume.

5.

Reprogram the new ECM.

Verifying Vehicle Repair

Verification of vehicle repair is more comprehensive for vehicles with OBD II system diagnostics. Following a repair, the techni-
cian should perform the following steps:

1.

Review and record the failure records and/or Freeze Frame data for the DTC which has been diagnosed (Freeze Frame data 
will only be stored for an A or B type diagnostic and only if the MIL has been illuminated).

2.

Clear DTC(s).

3.

Operate the vehicle within conditions noted in the failure records and/or Freeze Frame data.

OBD-6

On-Board Diagnostics

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4.

Monitor the DTC status information for the specific DTC which has been diagnosed until the diagnostic test associated with
that DTC runs and passes.

Following these steps is very important in verifying repairs on OBD II systems. Failure to follow these steps could result in unnec-
essary repairs.

Reprogramming of the ECM

The ECM can be reprogrammed with the use of the Tech 2 and the GM Technical Information System (TIS). Follow the steps out-
lined on the TIS.

TECH 2 INFORMATION

The “On-Board diagnostic (OBD) System Check” is an organized approach to identifying a problem created by a control module
system malfunction. It must be the starting point for any driveability complaint diagnosis, this will direct the service technician to
the next logical step in diagnosing the complaint. Understanding the chart and using it properly will reduce diagnostic time and
prevent the unnecessary replacement of good parts.

Tech 2 Diagnosis

The Tech 2(Figure OBD-1) checks function of the solenoids, sensors, and ECM. The Tech 2 connector is attached to the vehicle data link
connector(Figure OBD-2). The Tech 2 provides data on individual circuits, or on all the related electrical components in snap shot mode.

The ECM memory and circuits are interrogated by the Tech 2. The tool reads diagnostic trouble codes (DTC) and displays fault
and performance parameters.

Figure OBD-1:   TECH 2 

The recommended method for reading DTC(s) stored in memory is by using a Tech 2 plugged into the DLC (Figure OBD-1). 

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 On-Board Diagnostics  OBD-7

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Figure OBD-2:   Data Link Connector 

Malfunction Indicator Lamp (MIL) “Check Engine”

This light is on the instrument panel and has the following functions.

• It informs the driver that a problem has occurred and that the vehicle should be taken in for service as soon as reasonably 

possible.

As a bulb and system check, the light will come “ON” with the key “ON” and the engine not running. When the engine is started,
the light will turn “OFF.” If the light remains “ON,” the self-diagnostic system has detected a problem. If the problem goes away,
the light will go out in most cases after 10 seconds, but a DTC will remain stored in the ECM.

When the light remains “ON” while the engine is running, or when a malfunction is suspected due to a driveability or emissions
problem, an “On-Board Diagnostic (OBD) System Check” must be performed. This check will expose malfunctions which may
not be detected if other diagnostics are performed prematurely.

“Check Throttle” Lamp

This light is on the instrument panel and has the following functions:

• It informs the driver that a problem has occurred in the Accelerator Pedal Position (APP) circuit and the vehicle should be taken in 

for service as soon as reasonably possible.

As a bulb and system check, the light will come “ON” with the key “ON” for 2 seconds. If the light remains “ON,” the self-diag-
nostic system has detected a problem. If the problem goes away, the light will go out in most cases after 10 seconds, but a DTC will
remain stored in the ECM.

When the light remains “ON” while the engine is running, or when a malfunction is suspected, an “On-Board Diagnostic (OBD)
System Check” must be performed. This check will expose malfunctions which may not be detected if other diagnostics are per-
formed prematurely.

I.P. CLOSEOUT 

PANEL

DATA LINK

CONNECTOR