Hummer H2. Instruction - page 28

Low fuel pressure

Test pressure regulator and fuel pump, check for

restricted lines and filters

No distributor reference
pulses

Repair ignition system as necessary

Open coolant temperature
sensor circuit

Test sensor and wiring

Shorted W.O.T. switch in
T.P.S.

Disconnect W.O.T. switch, engine should start

Defective ECM

Replace ECM

Fuel tank residual pressure
valve leaks

Test for fuel pressure drop after shut down

Hard Starting

Disconnected hot air tube to
air cleaner

Reconnect tube and test control valve

Defective Idle Air Control
(IAC) valve

Test valve operation and circuit

Shorted, open or misadjusted
T.P.S.

Test and adjust or replace T.P.S.

EGR valve open

Test EGR valve and control circuit

Poor Oxygen sensor signal

Test for shorted or circuit

Incorrect mixture from PCV
system

Test PCV for flow, check sealing of oil filter cap

Poor High Speed Operation

Low fuel pump volume

Faulty pump or restricted fuel lines or filters

Poor MAP sensor signal

Test MAP sensor, vacuum hose and wiring

Poor Oxygen sensor signal

Test for shorted or open sensor or circuit

Open coolant temperature
sensor circuit

Test sensor and wiring

Faulty ignition operation

Check wires for cracks or poor con- nections, test

secondary voltage with oscilloscope

Contaminated fuel

Test fuel for water or alcohol

Intermittent ECM ground

Test ECM ground connection for resistance

Restricted air cleaner

Replace air cleaner

Restricted exhaust system

Test for exhaust manifold back pressure

Poor MAF sensor signal

Check leakage between sensor and manifold

Poor VSS signal

If tester for ALCL hook-up is available check that

VSS reading matches speedometer

Ping or Knock on Acceleration

Poor Knock sensor signal

Test for shorted or open sensor or circuit

Poor Baro sensor signal

Test for shorted or open sensor or circuit

Improper ignition timing

See VEHICLE EMISSION CONTROL LABEL

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

IGNITION SYSTEM TROUBLE SHOOTING

(where applicable)

Check for engine overheating
problems

Low coolant, loose belts or electric cooling fan

inoperative

NOTE:

For additional electronic fuel injection trouble shooting information, see the
appropriate article in the ENGINE PERFORMANCE section (not all vehicles have
Computer Engine Control articles). Information is provided there for diagnosing
fuel system problems on vehicles with electronic fuel injection.

NOTE:

This is GENERAL information. This article is not intended to be specific to any
unique situation or individual vehicle configuration. The purpose of this Trouble
Shooting information is to provide a list of common causes to problem
symptoms. For model-specific Trouble Shooting, refer to SUBJECT,
DIAGNOSTIC, or TESTING articles available in the section(s) you are accessing.

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

Fig. 3: Ignition Secondary Trouble Shooting Chart

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

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