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Hummer H1 (2006+). Manual - part 43

OBD-16

On-Board Diagnostics

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Ignition “OFF.”

Disconnect the ECM connectors.

Ignition “ON.”

Is the MIL “OFF”?

—

Go to step 6.

Go to step 18.

With the Scan Tool, check Engine Cal ID.
Is the proper CAL ID present?

—

Go to step 28.

Go to step 19.

With a test light to ground, probe the DLC connector
(pin 16).
Is the test light “ON”?

—

Go to step 8.

Go to step 20.

With a test light to B+, probe the DLC connector
(pins 4 and 5).
Is the test light “ON” for both circuits?

—

Go to step 9.

Go to step 21.

Check for proper operation of the cigar lighter.
Does the cigar lighter operate properly?

—

Go to step 10.

Go to step 22.

Verify proper operation of the Scan Tool with a known
good vehicle with the same equipment/controller.
Does the Scan Tool communicate with known good
vehicle?

—

Go to step 11.

Go to step 23.

Disconnect the Scan Tool.

With the DVM connected to ground, check the
ECM serial data line at the DLC connector (pin 2).

Is voltage on the serial data line less than the specified
value?

Go to step 12.

Go to step 15.

With the DVM connected to ground, again check the
ECM serial data line at the DLC connector (pin 2).
Is voltage on the serial data line less than the specified
value?

Go to step 13.

Go to step 16.

Ignition “OFF.”

With the DVM connected to ground, check resis-
tance of the serial data line at the DLC connector
(pin 2).

Is resistance less than the specified value?

10 Ohms

Go to step 14.

Go to step 27.

Disconnect the ECM connectors.

With the DVM connected to ground check resis-
tance of the serial data line at the DLC connector
(pin 2).

Is resistance less than the specified value?

10 Ohms

Go to step 24.

Go to step 28.

Ignition “OFF.”

Disconnect the ECM Connectors.

Ignition “ON.”

Check voltage on the DLC connector (pin 2).

Is voltage at the specified value?

Go to step 28.

Go to step 25.

Reprogram the EEPROM and retest.
Is serial data present?

—

Go to step 26.

Go to step 28.

No Scan Tool Data

Step

Action

Value(s)

Yes

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On-Board Diagnostics OBD-17

5745804

BASIC SYMPTOM CHECKS

Before using this section, you should perform the Diagnostic System Check that determines that:

• The control module and the malfunction indicator lamp (MIL) are operating correctly.

• There are no diagnostic trouble codes (DTCs) stored, or a DTC exists but without a MIL.

Several of the following symptom procedures call for a careful visual and physical check. The visual and physical checks are very
important. The checks can lead to correcting a problem without further checks which may save valuable time.

System OK.

—

Repair short to ground on the MIL control circuit.

—

Reprogram the EEPROM and retest.

—

Check fuse number 1H or the interior fuse box.

If fuse is blown, repair short to ground in the battery
feed circuit to the DLC connector (pin 16).

If the fuse is OK, repair open in the battery feed cir-
cuit to the DLC connector (pin 16).

—

Repair open in circuit that did not light the test light.
Refer to Section 12 for ground distribution.

—

Refer to Section 12 for cigar lighter repair.

—

Faulty Scan Tool and/or cable.

—

Repair short to ground in the serial data line.

—

Repair short to voltage in the serial data line.

—

System OK.

—

Check serial data line for an open.

If OK, check ECM and DLC connections.

If OK, replace the ECM.

NOTE: If the ECM is faulty, the new ECM must be pro-
grammed. Go to ECM replacement and programming
procedures.

Is the action complete?

—

Go to OBD

system check.

—

Replace the faulty ECM.

NOTE: If the ECM is faulty, the new ECM must be pro-
grammed. Go the ECM replacement and programming
procedures.

Is the action complete?

—

Go to OBD

system check.

—

No Scan Tool Data

Step

Action

Value(s)

Yes

OBD-18

On-Board Diagnostics

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Visual and Physical Checks

• Check to ensure that the control module grounds are clean, tight, and in their proper location.

• Check the vacuum hose for splits, kinks, and proper connections, as shown on the Vehicle Emission Control Information la-

bel.

• Check thoroughly for any type of leak or restriction.

• Check for air leaks at all of the mounting areas of the intake manifold sealing surfaces.

• Check the wiring for the following conditions:

• Proper connections

• Pinches

• Cuts

• The following symptom tables contain groups of possible causes for each symptom. The order of these procedures is not im-

portant. If the scan tool readings do not indicate the conditions, then proceed in a logical order, easiest to check or most
likely to cause first.

“On-Board Diagnostic (OBD) System Check”

After the visual/physical under hood inspection, the “On-Board Diagnostic (OBD) “System Check” is the starting point for all di-
agnostic procedures and for locating the cause of an emissions test failure.

The correct procedure to diagnose a fault is to follow three basic steps.

Are the on-board diagnostics working? This is determined by performing the “On-Board Diagnostic (OBD) System Check.” If
the on-board diagnostics are not working, refer to diagnostic charts in this section. If the on-board diagnostics are working
properly, the next step will be:

Is there a DTC stored? If a DTC is stored, go directly to the numbered DTC chart in this section. This will determine if the fault is
still present. If no DTC is stored, the next step will be:

Scan Tool serial data transmitted by the control module. This involves displaying the information available on the serial data stream
with a Scan Tool or one of the tools available for that purpose. Information on these tools and the meaning of the various displays can
be found in this section. Normal readings under a particular operating condition can be found below the chart “On-Board Diagnostic
(OBD) System Check.”

Tech 2 Use With Intermittents

In some situations the Tech 2 data update rate makes the tool less effective than a voltmeter, such as when trying to detect an intermittent
problem which lasts for a very short time. However, the Tech 2 allows manipulation of wiring harnesses or components under the hood
with the engine not running, while observing the Tech 2 readout.

The Tech 2 can be plugged in and observed while driving the vehicle under the condition when the MIL “Service Engine Soon” light
turns “ON” momentarily or when the engine driveability is momentarily poor. If the problem seems to be related to certain parameters
that can be checked on the Tech 2, they should be checked while driving the vehicle. If there does not seem to be any correlation between
the problem and any specific circuit, the Tech 2 can be checked on each position, watching for a period of time to see if there is any
change in the reading that indicates intermittent operation.

The Tech 2 is also an easy way to compare the operating parameters of a poorly operating engine with those of a known good one. For ex-
ample, a sensor may shift in value but not set a DTC. Comparing the sensor’s readings with those of a known good vehicle may uncover
the problem.

The Tech 2 has the ability to save time in diagnosis and prevent the replacement of good parts. The key to using the Tech 2 successfully
for diagnosis lies in the technician’s ability to understand the system he is trying to diagnose as well as understanding of the Tech 2 oper-
ation and limitations.

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On-Board Diagnostics OBD-19

5745804

Symptoms

Verify the customer complaint. Locate the correct symptom table. Check the items indicated under that symptom from the follow-
ing symptom tables:

• Engine Cranks but Does Not Run

• Intermittent Conditions

• Hard Start

• Surges/Chugs

• Lack of Power, Sluggishness, or Sponginess

• Fuel Knock/Combustion Noise

• Hesitation, Sag, Stumble

• Cuts Out, Misses

• Poor Fuel Economy

• Excessive Smoke

Symptom – Engine Cranks But Does Not Run

Circuit Description

This table verifies that all the basic engine systems are operating properly. This includes the battery condition, the engine cranking
speed, the glow plugs, and the fuel delivery system.

Diagnostic Aids

If the cause of an engine cranks but will not run condition has not been found, inspect for the following conditions:

• Hard starting only in cold ambient temperatures. These may cause an intermittent condition that may not occur in the service

bay:

• Fuel heater inoperative.

• Ice blockage at the fuel pickup in the fuel tank--This will be a high vacuum in the supply lines while cranking, and the

problem will disappear after the vehicle is brought in the service bay. It may also exhibit a start and stall condition or a
starting condition with no acceleration.

• The correct cranking speed is 100 RPM cold and 180 RPM hot.

• Water or foreign material in fuel system.

• A basic engine problem.

• More than 1 ohm of resistance in the ignition voltage circuit to the fuel injection control module may cause a crank but no

start condition.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

This step tests for an ignition 1 voltage supply to the engine control module (ECM).

If there is fuel in the engine oil, fuel may be leaking from the fuel injector or fuel injection pump into the crankcase.

If the fuel system will not even briefly prime to 10 psi and will not start, the check valve in the fuel filter/heater element

housing is stuck open.

This step determines if the fuel system is bleeding down causing a no start. The fuel pressure will slowly drop to 0 psi, but

should still be above 8 psi 10 seconds after pressurizing the fuel system.

In some cases, no compression, possibly with excessive fuel, in a single cylinder can cause a no start.

10.

This step determines if the problem is a stuck open or broken fuel injector. If fuel vapors come out of any of the glow plug

holes, excessive fuel is being sent into a cylinder, and not being distributed to all of the fuel injectors.

11.

The engine will not run without an actual fuel rail pressure more than 10 MPa (1,450 psi).

05-03-06

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