Engine Controls - Trouble Shooting - No Codes - 8.1L: Diagnosis Chevrolet Silverado 1500 HD

PRELIMINARY INSPECTION

1. Verify on-board diagnostics are working by performing «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-158433-S21464854222003092600000) in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
2. Ensure PCM and MIL functions properly.
3. Ensure no DTCs (except intermittent) are stored.
4. Perform fuel system pressure test. See «FUEL SYSTEM PRESSURE TEST»(ref-152743-S07134794452003022400000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
5. Visually inspect all systems.

After all checks have been performed, verify customer complaint and locate correct symptom. Check items indicated under that symptom. See SYMPTOMS .

SYMPTOMS

Note. Before proceeding with any symptom diagnosis, perform PRELIMINARY INSPECTION .

Note. If PCM displays data but engine fails to start, see NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.

SYMPTOM DIAGNOSIS

Symptom checks should not be used unless symptom occurs while vehicle is being tested. To reduce diagnostic time, ensure steps in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL and DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL articles were performed before diagnosing a symptom. Symptoms available for diagnosis include

1. «DETONATION/SPARK KNOCK»(ref-153006-S22648768692003031000000)
2. «ENGINE BACKFIRES»(ref-153006-S42652715212003031000000)
3. «ENGINE CUTS OUT, MISSES»(ref-153006-S37537508932003031000000)
4. «ENGINE DIESELING/RUN-ON»(ref-153006-S19185558632003031000000)
5. «HARD START»(ref-153006-S10937946262003031000000)
6. «HESITATION, SAG OR STUMBLE»(ref-153006-S31303299062003031000000)
7. «LACK OF POWER OR SLUGGISH»(ref-153006-S05790491002003031000000)
8. «POOR FUEL ECONOMY»(ref-153006-S06551303422003031000000)
9. «POOR FUEL FILL QUALITY»(ref-153006-S19386532172003031000000)
10. «ROUGH, UNSTABLE OR INCORRECT IDLE & STALLING»(ref-153006-S17739735782003031000000)
11. «VEHICLE SURGES OR CHUGGLES»(ref-153006-S11393333082003031000000)

Symptom Definition

A mild to severe ping, usually worse during acceleration. Engine makes sharp metallic knocks which change with degree of acceleration.

Fuel ignites within intake manifold or in exhaust system, making a loud popping noise.

Cuts out, misses is defined as a steady pulsation or jerking following engine speed, usually more pronounced as engine load increases. Exhaust may have a steady spitting sound at idle or low speed. Perform visual inspection as described in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.

Engine continues to run (but very rough) after ignition is turned off. If engine runs smoothly, check ignition switch.

Engine cranks okay, but does not start immediately. Engine eventually starts and may run okay or soon stall.

Momentary lack of response when accelerator is pushed down. May occur at any vehicle speed. Usually occurs after a stop. If severe enough, may cause engine to stall.

Engine delivers less power than expected. Little or no increase in speed when accelerator is applied.

Fuel economy, as measured by an actual road test, is noticeably lower than expected. Current fuel economy is noticeably lower than previous fuel economy.

Difficult to fill.

Overfill.

Premature shut-off of the fuel dispensing nozzle.

Fuel spit back.

Liquid fuel in the EVAP canister.

Liquid fuel leak.

Fuel odor.

Engine runs unevenly at idle. If bad enough, vehicle will shake. Idle RPM may vary. Engine idles at incorrect RPM.

Engine power varies under steady throttle or cruise. Feels like vehicle speeds up and slows down even though accelerator pedal position remains constant.

SCAN TOOL SNAPSHOT

The scan tool can be set up to take a snapshot of the parameters available via serial data. The snapshot function records live data over a period of time. The recorded data can be played back and analyzed. The scan tool can also graph parameters singly or in combinations of parameters for comparison. The snapshot can be triggered manually at the time the symptom is noticed, or set up in advance to trigger when a DTC sets. An abnormal value captured in the recorded data may point to a system or component that needs to be investigated further. Refer to scan tool user instructions for more information on the Snapshot function.

See also:
• ON-VEHICLE ADJUSTMENT - TRUCKS - EXCEPT TRACKER