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Engine Controls - Trouble Shooting - No Codes - 8.1L: Other Chevrolet Suburban X

Testing & Diagnostics ~6084 words

Possible Causes & Corrections

Check the following items

  1. Search for bulletins.
  2. Verify that the PCM grounds are clean, tight, and in the proper locations.
  3. If there are no engine mechanical faults, fill the fuel tank with a known high quality fuel that meets the vehicles minimum octane requirements. Road test the vehicle and re-evaluate the vehicles performance.
  4. Check fuel pressure. 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. Inspect for a restricted fuel filter.
  6. Inspect for a contaminated fuel condition.
  7. Inspect for conditions that can cause engine to run lean: Water intrusion in HO2S connector, exhaust leak between HO2S and engine, vacuum leaks, incorrect fuel pressure, restricted fuel injectors, inaccurate MAF sensor, fuel contamination, or vacuum hoses that are split, kinked, or improperly connected.
  8. Verify that spark plugs are of proper heat range.
  9. Low engine coolant.
  10. Restricted air flow to radiator or restricted coolant flow through the radiator.
  11. Inoperative cooling fan
  12. Excessive oil in combustion chamber, may be caused by leaking valve seals.
  13. Low cylinder compression. See CYLINDER COMPRESSION PRESSURE under «MECHANICAL INSPECTION»(ref-152876-S35504444782003030100000) under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  14. Combustion chambers for excessive carbon buildup. Clean combustion chamber by using top engine cleaner.
  15. Inspect for incorrect basic engine parts. Such as, camshaft, cylinder heads, pistons, etc.
  16. Inspect the Park/Neutral Position (PNP) switch operation.
  17. Inspect transmission Torque Converter Clutch (TCC) operation. See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. The TCC applying too soon can cause the engine to spark knock.

Check the following items

  1. Search for bulletins.
  2. Verify that PCM grounds are clean, tight, and in the proper locations.
  3. Inspect for incorrect fuel pressure. See «FUEL SYSTEM PRESSURE TEST»(ref-152743-S07134794452003022400000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  4. Inspect for a restricted fuel filter.
  5. Inspect fuel injectors. See «FUEL SYSTEMS»(ref-153339-S38028309172003040200000) in SYSTEM & COMPONENT TESTING - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  6. Verify that each injector harness is connected to the correct injector or cylinder. Relocate injector harnesses as necessary.
  7. Inspect Secondary Air Injection (AIR) system. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-158433-S36149293242003092600000) in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  8. Inspect air intake system and crankcase for air leaks.
  9. Inspect crankcase ventilation valve for proper operation. Place a finger over the inlet hole in the valve end several times. The valve should snap back. If not, replace PCV valve.
  10. Inspect for an inaccurate speedometer.
  11. Use a scan tool in order to monitor the Knock Sensor (KS) system for excessive spark retard activity.
  12. Inspect for proper ignition voltage output using Spark Tester (J-26792).
  13. Remove spark plugs and inspect for wet plugs, cracks, wear, improper gap, burned electrodes or heavy deposits.
  14. An improper spark plug gap will cause a driveability problem.
  15. Determine cause of fouling before replacing spark plugs.
  16. Visually and physically inspect secondary ignition for ignition wires arcing to ground or ignition coils arcing to ground.
  17. Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply the water.
  18. Monitor the Misfire Current Counters while driving the vehicle in the conditions that the misfire occurred. If a misfiring cylinder can be located, use DTC P0300 diagnostic procedures for diagnosis. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-158433-S36149293242003092600000) in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  19. Inspect for loose ignition coil grounds. See «ELECTRONIC IGNITION SYSTEM DIAGNOSIS»(ref-153339-S42555566212003040200000) under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  20. Inspect engine for low coolant level.
  21. Inspect engine thermostat for proper operation and for correct heat range.
  22. Inspect engine mechanical for compression, worn camshaft lobes, valve timing, bent push rods, worn rocker arms, broken valve springs, excessive oil in combustion chamber or leaking valve seals. See CYLINDER COMPRESSION PRESSURE under «MECHANICAL INSPECTION»(ref-152876-S35504444782003030100000) under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  23. For incorrect basic engine parts. Inspect camshaft, cylinder heads, pistons, etc.
  24. Visually and physically inspect the vacuum hoses for splits, kinks, and proper connections and routing as shown on the underhood Vehicle Emission Control Information label.
  25. Inspect intake manifold and exhaust manifold passages for casting flash.
  26. Inspect the transmission Torque Converter Clutch (TCC) operation. See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. The scan tool should indicate an RPM drop when TCC is commanded ON.
  27. Inspect exhaust system for possible restrictions. Inspect exhaust system for damaged or collapsed pipes. Inspect the mufflers for heat distress or possible internal failure. Inspect for possible plugged catalytic converters.
  28. Electromagnetic Interference (EMI) on the reference circuit can cause an engine miss condition. A scan tool can usually detect EMI by monitoring engine RPM. A sudden increase in RPM with little change in actual engine RPM change may indicate that EMI is present. If a problem exists, inspect for high voltage components near ignition control circuits.
  29. Inspect Park/Neutral Position (PNP) switch operation.
  30. Inspect for faulty motor mounts.
  31. Inspect intake and exhaust manifold passages for casting flash.

Check the following items

  1. Search for bulletins.
  2. Verify that PCM grounds are clean, tight and in the proper locations.
  3. Remove air filter element and inspect for dirt and for restrictions.
  4. Inspect fuel injectors. See «FUEL SYSTEMS»(ref-153339-S38028309172003040200000) in SYSTEM & COMPONENT TESTING - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  5. Inspect for incorrect fuel pressure. See «FUEL SYSTEM PRESSURE TEST»(ref-152743-S07134794452003022400000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  6. Inspect for a restricted fuel filter.
  7. Inspect for a contaminated fuel condition.
  8. Inspect for conditions that may cause engine to run rich: Water intrusion in HO2S connector, engine oil contaminated by fuel, EVAP canister purge condition, incorrect fuel pressure, leaking fuel pressure regulator, leaking fuel injectors, inaccurate MAF sensor, blockage MAF sensor inlet screen, vacuum hoses that are split, kinked, or improperly connected, air intake duct that is collapsed or restricted, or air filter that is dirty or restricted.
  9. Inspect for conditions that may cause engine to run lean: Water intrusion in HO2S connector, exhaust leak between HO2S and engine, vacuum leaks, incorrect fuel pressure, restricted fuel injectors, inaccurate MAF sensor, fuel contamination or vacuum hoses that are split, kinked, or improperly connected.
  10. Monitor Knock Sensor (KS) system for excessive spark retard activity.
  11. Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply water.
  12. Test for proper ignition voltage output with a Spark Tester (J-26792).
  13. Remove spark plugs and inspect for correct heat range, wet plugs, cracks, wear, improper gap, burned electrodes or heavy deposits.
  14. An improper spark plug gap will cause a driveability problem.
  15. Determine cause of the fouling before replacing spark plugs.
  16. Visually and physically inspect the secondary ignition for ignition wires arcing to ground, ignition wires for proper engagement to spark plug or ignition coils for cracks or carbon tracking.
  17. Using scan tool, monitor the Misfire Current Counters while driving vehicle in the conditions that the misfire occurred. If a misfiring cylinder can be located, use DTC P0300 diagnostic procedures for diagnosis. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-158433-S36149293242003092600000) in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  18. Inspect engine mechanical for compression, sticking or leaking valves, worn camshaft lobes, valve timing, bent push rods, worn rocker arms, broken valve springs or excessive oil in combustion chamber, caused by leaking valve seals. See CYLINDER COMPRESSION PRESSURE under «MECHANICAL INSPECTION»(ref-152876-S35504444782003030100000) under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  19. For incorrect basic engine parts. Inspect camshaft, cylinder heads, pistons, etc.
  20. Inspect for excessive crankshaft end play that will cause the CKP sensor reluctor wheel to move out of alignment with the CKP sensor. This could result in a no-start, a start and stall, or an erratic performance.
  21. Inspect exhaust system for possible restrictions. Inspect exhaust system for damaged or collapsed pipes. Inspect mufflers for heat distress or possible internal failure. Inspect for possible plugged catalytic converters.
  22. Electromagnetic Interference (EMI) on the reference circuit can cause an engine misfire condition. A sudden increase in indicated RPM with little change in actual engine RPM change indicates EMI is present. Inspect for high voltage components near ignition control circuits if a condition exists.
  23. Inspect intake and exhaust manifold passages for casting flash.

Check for the following

  1. Search for bulletins.
  2. Verify that PCM grounds are clean, tight and in the proper locations.
  3. Inspect fuel injectors for leakage or diagnose fuel system. See «FUEL SYSTEM PRESSURE TEST»(ref-152743-S07134794452003022400000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.

Check the following items

  1. Verify that the powertrain control module (PCM) grounds are clean, tight, and in the proper locations.
  2. Search for bulletins.
  3. Monitor Engine Coolant Temperature (ECT) sensor with scan tool. Compare engine coolant temperature with the ambient air temperature on a cold engine. If coolant temperature reading is more than 5 degrees more or less than the ambient air temperature on a cold engine, check for high resistance in the coolant sensor circuit.
  4. Inspect Mass Airflow (MAF) sensor installation. A MAF sensor that is incorrectly installed may cause a hard start condition. The embossed arrows on MAF sensor indicate direction of intake air flow. The arrows must point toward engine. Install MAF sensor in proper direction.
  5. Inspect Camshaft Position (CMP) sensor for proper mounting and/or a bad connection. An extended crank occurs if PCM does not receive a CMP signal.
  6. Check fuel pump relay operation. See «FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS»(ref-153339-S42480524892003041600000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  7. A faulty in-tank fuel pump check valve allows fuel in the lines to drain back to the tank after the engine stops. See «FUEL SYSTEM PRESSURE TEST»(ref-152876-S29682748142003030100000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  8. Verify that both fuel injector fuses are not open. An open fuel injector fuse causes four injectors and four ignition coils not to operate. Inspect the injector circuits and the ignition coil circuits for an intermittent short to ground. Replace the fuse.
  9. Check fuel pressure. See «FUEL SYSTEM PRESSURE TEST»(ref-152876-S29682748142003030100000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  10. Inspect for a restricted fuel filter.
  11. Inspect for a contaminated fuel condition.
  12. Verify that both fuel injector fuses are not open. An open fuel injector fuse causes four ignition coils and four fuel injectors not to operate. Inspect the ignition coil circuits and the fuel injector circuits for an intermittent short to ground.
  13. Inspect for proper ignition voltage output with a Spark Tester (J-26792).
  14. Remove spark plugs and inspect for correct heat range, wet plugs, cracks, wear, improper gap, burned electrodes or heavy deposits.
  15. Determine cause of the conditions before replacing spark plugs.
  16. Inspect for bare or shorted ignition wires.
  17. Inspect for loose ignition coil grounds. See «ELECTRONIC IGNITION SYSTEM DIAGNOSIS»(ref-153339-S42555566212003040200000) under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  18. Excessive oil in combustion chamber or leaking valve seals.
  19. Low cylinder compression. See CYLINDER COMPRESSION PRESSURE under «MECHANICAL INSPECTION»(ref-152876-S35504444782003030100000) under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  20. Combustion chambers for excessive carbon buildup. Clean chambers using top engine cleaner.
  21. Incorrect basic engine parts. Inspect cylinder heads, camshafts, pistons, etc.

Check for the following items

  1. Search for bulletins.
  2. Verify that PCM grounds are clean, tight and in the proper locations.
  3. Check fuel pressure. See «FUEL SYSTEM PRESSURE TEST»(ref-152876-S29682748142003030100000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  4. Inspect for a restricted fuel filter.
  5. Inspect for a contaminated fuel condition.
  6. Verify that both fuel injector fuses are not open. An open fuel injector fuse causes 4 ignition coils and 4 fuel injectors not to operate. Inspect ignition coil circuits and fuel injector circuits for an intermittent short to ground.
  7. Inspect fuel injectors. Refer «SYSTEM & COMPONENT TESTING - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL»(ref-153339) article.
  8. Inspect cause for engine to run rich: Water intrusion in HO2S connector, engine oil contaminated by fuel, EVAP canister purge condition, incorrect fuel pressure, leaking fuel pressure regulator, leaking fuel injectors, inaccurate MAF sensor, blockage on MAF sensor inlet screen, vacuum hoses that are split, kinked, or improperly connected, air intake duct that is collapsed or restricted, or an air filter that is dirty or restricted.
  9. Inspect cause for engine to run lean: Water intrusion in HO2S connector, exhaust leak between HO2S and engine, vacuum leaks, incorrect fuel pressure, restricted fuel injectors, inaccurate MAF sensor, fuel contamination, or vacuum hoses that are split, kinked, or improperly connected.
  10. Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply water.
  11. Test for proper ignition voltage output with Spark Tester (J-26792).
  12. Remove spark plugs and check for correct heat range, wet plugs, cracks, wear, improper gap, burned electrodes or heavy deposits.
  13. An improper spark plug gap will cause a driveability problem. Gap spark plugs using a wire gauge gap tool.
  14. Determine cause of the fouling before replacing spark plugs.
  15. Using scan tool, monitor the Misfire Current Counters while driving the vehicle in the conditions that the misfire occurred. If a misfiring cylinder can be located, use DTC P0300 diagnostic procedures for diagnosis. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-158433-S36149293242003092600000) in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  16. Inspect for loose ignition coil grounds.
  17. Inspect engine thermostat for proper operation and for proper heat range.
  18. Inspect generator output voltage. Repair charging system if generator output voltage is less than 9 volts or more than 16 volts.

Check the following items

  1. Search for bulletins.
  2. Verify that PCM grounds are clean, tight and in the proper locations.
  3. Remove air filter element and inspect for dirt or for restrictions.
  4. Inspect both injector fuses for being open. An open injector fuse causes 4 ignition coils and 4 injectors not to operate. Replace fuse. Inspect the ignition coil circuits and injector circuits for an intermittent short to ground.
  5. Inspect for incorrect fuel pressure. See «FUEL SYSTEM PRESSURE TEST»(ref-152876-S29682748142003030100000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  6. Inspect for a restricted fuel filter, contaminated fuel, or improper fuel pressure. See «FUEL SYSTEM PRESSURE TEST»(ref-152876-S29682748142003030100000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  7. Inspect fuel injectors. See «FUEL SYSTEMS»(ref-153339-S38028309172003040200000) in SYSTEM & COMPONENT TESTING - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  8. Inspect for a contaminated fuel condition.
  9. Inspect cause for engine to run rich: Water intrusion in HO2S connector, engine oil contaminated by fuel, EVAP canister purge condition, incorrect fuel pressure, leaking fuel pressure regulator, leaking fuel injectors, inaccurate MAF sensor, blockage on MAF sensor inlet screen, vacuum hoses that are split, kinked or improperly connected, air intake duct that is collapsed or restricted, or air filter that is dirty or restricted.
  10. Inspect cause for engine to run lean: Water intrusion in HO2S connector, exhaust leak between HO2S and engine, vacuum leaks, incorrect fuel pressure, restricted fuel injectors, inaccurate MAF sensor, fuel contamination, or vacuum hoses that are split, kinked or improperly connected.
  11. Use a scan tool in order to monitor the Knock Sensor (KS) system for excessive spark retard activity.
  12. Verify that both fuel injector fuses are not open. An open fuel injector fuse causes 4 ignition coils and 4 fuel injectors not to operate. Inspect ignition coil circuit and injector circuits for an intermittent short to ground.
  13. Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as water is applied.
  14. Inspect for proper ignition voltage output with Spark Tester (J-26792).
  15. Remove spark plugs and inspect for correct heat range, wet plugs, cracks, wear, improper gap, burned electrodes or heavy deposits.
  16. An improper spark plug gap will cause a driveability problem. Gap spark plugs using a wire gauge gap tool.
  17. Determine the cause of fouling before replacing spark plugs.
  18. Monitor the Misfire Current Counters while driving the vehicle within the conditions that the misfire occurred. If a misfiring cylinder can be located with a misfire, use DTC P0300 diagnostic procedures for diagnosis. See DTC P0300 in «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-158433-S36149293242003092600000) in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  19. Inspect for loose ignition coil grounds.
  20. Verify that the engine coolant temperature is not above 266°F (130°C). This condition causes the PCM to operate in Engine Coolant Over Temperature - Fuel Disabled Mode. While in Engine Coolant Over Temperature - Fuel Disabled Mode, the PCM will disable the fuel injectors to 4 cylinders at a time to keep engine temperatures from reaching damaging levels. The driver may perceive the Engine Coolant Over Temperature - Fuel Disabled Mode as a lack of power, miss or rough idle. If vehicle operates in this condition, diagnose engine overheating.
  21. Inspect for excessive oil in the combustion chambers. May be caused by leaking valve seals.
  22. Test for low cylinder compression. See CYLINDER COMPRESSION PRESSURE under «MECHANICAL INSPECTION»(ref-152876-S35504444782003030100000) under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  23. Inspect for incorrect basic engine parts. Inspect camshaft, cylinder heads, pistons, etc.
  24. Inspect exhaust system for possible restrictions. Inspect exhaust system for damaged or collapsed pipes. Inspect the mufflers for heat distress or internal failure. Inspect for plugged catalytic converters.
  25. Inspect transmission Torque Converter Clutch (TCC) for proper operation. See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.

Check the following items

  1. Search for bulletins.
  2. Verify that PCM grounds are clean, tight and in the proper locations.
  3. Inspect the owner's driving habits. Is the A/C ON or the defroster mode ON full time? Are the tires at the correct pressure? Are the wheels and tires the correct size? Are there excessively heavy loads being carried? Is the acceleration rate too much, too often? Remove air filter element and inspect for dirt or for restrictions. Replace as necessary.
  4. Inspect the type, quality and alcohol content of fuel. Oxygenated fuels have lower energy and may deliver reduced fuel economy.
  5. Inspect fuel injectors. See «SYSTEM & COMPONENT TESTING - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL»(ref-153339) article.
  6. Inspect for incorrect fuel pressure. See «FUEL SYSTEM PRESSURE TEST»(ref-152876-S29682748142003030100000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  7. Inspect for a restricted fuel filter.
  8. Inspect for a contaminated fuel condition.
  9. Ensure that each fuel injector harness is connected to the correct injector and cylinder. Relocate the injector harnesses as necessary.
  10. Inspect for foreign material accumulation in the throttle bore, coking on the throttle valve, or on the throttle shaft.
  11. Inspect cause for engine to run rich: Water intrusion in HO2S connector, engine oil contaminated by fuel, EVAP canister purge condition, incorrect fuel pressure, leaking fuel pressure regulator, leaking fuel injectors, inaccurate MAF sensor, blockage on MAF sensor inlet screen, vacuum hoses that are split, kinked or improperly connected, air intake duct that is collapsed or restricted, or air filter that is dirty or restricted.
  12. Inspect air intake system and crankcase for air leaks.
  13. Inspect crankcase ventilation valve for proper operation. See «EMISSION SYSTEMS & SUB-SYSTEMS»(ref-153339-S09940903322003040200000) in SYSTEM & COMPONENT TESTING - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  14. Inspect for an inaccurate speedometer.
  15. Use scan tool in order to monitor the Knock Sensor (KS) system for excessive spark retard activity.
  16. Inspect for proper ignition voltage output with Spark Tester (J-26792).
  17. Remove spark plugs and inspect for wet plugs, cracks, wear, improper gap, burned electrodes or heavy deposits.
  18. An improper spark plug gap will cause a driveability problem.
  19. Determine the cause of fouling before replacing spark plugs.
  20. Visually and physically inspect the secondary ignition for ignition wires arcing to ground or ignition wires for proper routing.
  21. Soaking the secondary ignition system with water from a spray bottle may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply water.
  22. Inspect for loose ignition coil grounds. See «ELECTRONIC IGNITION SYSTEM DIAGNOSIS»(ref-153339-S42555566212003040200000) under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  23. Inspect for low engine coolant level.
  24. Inspect engine thermostat for proper operation and for correct heat range.
  25. Inspect engine mechanical for compression, sticking or leaking valves, worn camshaft lobes, valve timing, bent push rods, worn rocker arms, broken valve springs or excessive oil in combustion chamber, caused by leaking valve seals. See CYLINDER COMPRESSION PRESSURE under «MECHANICAL INSPECTION»(ref-152876-S35504444782003030100000) under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  26. Inspect for incorrect basic engine parts. Inspect camshaft, cylinder heads, pistons, etc.
  27. Visually and physically check the vacuum hoses for splits, kinks, and proper connections and routing as shown on the underhood Vehicle Emission Control Information label.
  28. Inspect transmission Torque Converter Clutch (TCC) operation. See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. The scan tool should indicate a RPM drop, when the system commands the TCC ON.
  29. Inspect exhaust system for a possible restriction. Inspect exhaust system for damaged or collapsed pipes. Inspect the mufflers for heat distress or possible internal failure. Inspect for possible plugged catalytic converters.
  30. Electromagnetic Interference (EMI) on the reference circuit can cause an engine miss condition. A scan tool can usually detect EMI by monitoring the engine RPM. A sudden increase in RPM with little change in actual engine RPM change indicates EMI is present. Inspect for high voltage components near ignition control circuits, if a condition exists.
  31. Inspect the Park/Neutral Position (PNP) switch circuit.
  32. Inspect brake system for dragging or improper operation. Verify that operator does not drive with a foot on the brake pedal.

Check the following items

  1. Check valve is stuck closed.
  2. Fill limiter vent valve is stuck closed.
  3. Evaporative Emission (EVAP) canister is restricted.
  4. EVAP canister vent solenoid is stuck closed.
  5. Restricted EVAP pipes.
  6. High Reid Vapor Pressure (RVP).
  7. High fuel temperature.
  8. The fuel filler hose/pipe is pinched, kinked or blocked.
  9. The fuel feed hose or crossover hose is pinched, kinked or blocked.
  10. The ignition switch is on.

Check the following items

  1. Pressure relief valve in fill limiter vent valve is stuck open.
  2. Pressure relief valve in fill limiter vent is valve leaking.
  3. Fill limiter vent valve is stuck open.
  4. Fill limiter vent valve is leaking.

Check the following items

  1. Check valve is stuck closed.
  2. Fill limiter vent valve is stuck closed.
  3. EVAP canister is restricted.
  4. EVAP canister vent solenoid is stuck closed.
  5. EVAP canister is restricted.
  6. EVAP canister vent solenoid is stuck closed.
  7. Restricted EVAP pipes.
  8. High Reid Vapor Pressure (RVP).
  9. High fuel temperature.
  10. The fuel filler hose/pipe is pinched, kinked or blocked.
  11. The fuel feed hose or crossover hose is pinched, kinked or blocked.
  12. The ignition switch is on.

Check the following items

  1. Check valve is stuck open.
  2. Check valve is stuck closed.
  3. Check valve is leaking.
  4. High Reid Vapor Pressure (RVP).
  5. High fuel temperature.

Check the following items

  1. Fill limiter vent valve is stuck open.
  2. Fill limiter vent valve is leaking.

Check the following items

  1. Pressure relief valve in fill limiter vent valve is stuck open.
  2. Pressure relief valve in fill limiter vent valve is leaking.
  3. Fuel filler hose is loose or torn.
  4. Fuel feed hose or crossover hose is loose or torn.
  5. Fill limiter vent valve is stuck open.

Check the following items

  1. Pressure relief valve in fill limiter vent valve is stuck open.
  2. Pressure relief valve in fill limiter vent valve is leaking.
  3. EVAP canister is saturated.

Check the following items

  1. Search for bulletins.
  2. Verify that PCM grounds are clean, tight and in the proper locations.
  3. Remove and inspect the air filter element for dirt or for restrictions.
  4. Inspect fuel injectors. See «FUEL INJECTOR COIL TEST»(ref-153339-S13092179522003040200000) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  5. Check fuel pressure. See «FUEL SYSTEM PRESSURE TEST»(ref-152876-S29682748142003030100000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  6. Inspect for a restricted fuel filter.
  7. Inspect for a contaminated fuel condition.
  8. Ensure that each fuel injector harness is connected to the correct injector/cylinder. Relocate fuel injector harnesses as necessary.
  9. Inspect cause for engine to run rich: Water intrusion in HO2S connector, engine oil contaminated by fuel, EVAP canister purge condition, incorrect fuel pressure, leaking fuel pressure regulator, leaking fuel injectors, inaccurate MAF sensor, blockage on MAF sensor inlet screen, vacuum hoses that are split, kinked or improperly connected, air intake duct that is collapsed or restricted or air filter that is dirty or restricted.
  10. Inspect cause for engine to run lean: Water intrusion in HO2S connector, exhaust leak between HO2S and engine, vacuum leaks, incorrect fuel pressure, restricted fuel injectors, inaccurate MAF sensor, fuel contamination, or vacuum hoses that are split, kinked or improperly connected.
  11. Inspect crankcase ventilation valve for proper operation. See «EMISSION SYSTEMS & SUB-SYSTEMS»(ref-153339-S09940903322003040200000) in SYSTEM & COMPONENT TESTING - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  12. Use a scan tool in order to monitor the Knock Sensor (KS) system for excessive spark retard activity.
  13. Inspect for proper ignition voltage output with Spark Tester (J-26792).
  14. Remove spark plugs and check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits.
  15. An improper spark plug gap will cause a driveability problem. Gap spark plugs using a wire gauge gap tool.
  16. Determine the cause of fouling before replacing spark plugs.
  17. Visually and physically inspect secondary ignition for ignition wires arcing to ground or ignition wires for proper routing.
  18. Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply water.
  19. Monitor the Misfire Current Counters while driving the vehicle in the conditions that the misfire occurred. If a misfiring cylinder can be located, use DTC P0300 diagnostic procedures for diagnosis. See DTC P0300 in «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-158433-S36149293242003092600000) in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  20. Inspect for loose ignition coil grounds. See «ELECTRONIC IGNITION SYSTEM DIAGNOSIS»(ref-153339-S42555566212003040200000) under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  21. Inspect engine mechanical for compression, sticking or leaking valves, worn camshaft lobes, valve timing, bent push rods, worn rocker arms, broken valve springs or excessive oil in combustion chamber, caused by leaking valve seals. See CYLINDER COMPRESSION PRESSURE under «MECHANICAL INSPECTION»(ref-152876-S35504444782003030100000) under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  22. Inspect for incorrect basic engine parts. Inspect camshaft, cylinder heads, pistons, etc.
  23. Inspect for excessive crankshaft end play that will cause the CKP sensor reluctor wheel to move out of alignment with the CKP sensor. This could result in a no-start, a start and stall or an erratic performance.
  24. Inspect the exhaust system for possible restrictions. Inspect for damaged or collapsed pipes. Inspect mufflers for heat distress or possible internal failure. Inspect for possible plugged catalytic converters.
  25. Electromagnetic Interference (EMI) on the reference circuit can cause an engine miss condition. A scan tool can usually detect EMI by monitoring the engine RPM. A sudden increase in RPM with little change in actual engine RPM change indicates that EMI is present. If a problem exists, inspect routing of secondary ignition wires or high voltage components near the ignition control circuits.
  26. Inspect Park/Neutral Position (PNP) switch circuit.
  27. Inspect for faulty motor mounts.
  28. Inspect intake and exhaust manifold passages for casting flash.
  29. Inspect for a stuck open EGR valve or EGR pintle not seating properly. Inspect EGR valve gasket for leaks.

Check for the following items

  1. Search for bulletins.
  2. Inspect PCM grounds for being clean, tight and in the proper locations.
  3. Verify the driver understands the operation of the transmission Torque Converter Clutch (TCC) and A/C compressor operation as explained in the owner's manual. Inform customer how the TCC and A/C clutch operates.
  4. Inspect HO2S. The HO2S should respond quickly to different throttle positions. If they do not, inspect HO2S for silicone or other contaminates from fuel or use of improper RTV sealant. The sensors may have a White , powdery coating and result in a high but false signal voltage rich exhaust indication. The PCM will then reduce the amount of fuel delivered to the engine causing a severe driveability problem.
  5. Inspect the Mass Airflow (MAF) sensor connections. Repair or replace damaged terminals.
  6. Test for incorrect fuel pressure. See «FUEL SYSTEM PRESSURE TEST»(ref-152876-S29682748142003030100000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  7. Inspect for a restricted fuel filter.
  8. Inspect for a contaminated fuel condition.
  9. Verify that each injector harness is connected to the correct injector or cylinder. Relocate injector harnesses as necessary.
  10. Inspect cause for engine to run rich: Water intrusion in HO2S connector, engine oil contaminated by fuel, EVAP canister purge condition, incorrect fuel pressure, leaking fuel pressure regulator, leaking fuel injectors, inaccurate Mass Airflow (MAF) sensor, blockage on MAF sensor inlet screen, vacuum hoses that are split, kinked or improperly connected, air intake duct that is collapsed or restricted or air filter that is dirty or restricted.
  11. Inspect cause for engine to run lean: Water intrusion in HO2S connector, exhaust leak between HO2S and engine, vacuum leaks, incorrect fuel pressure, restricted fuel injectors, inaccurate MAF sensor, fuel contamination or vacuum hoses that are split, kinked or improperly connected.
  12. Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring
  13. Test for proper ignition voltage output with Spark Tester (J-26792).
  14. Remove spark plugs and inspect for correct heat range, wet plugs, cracks, wear, improper gap, burned electrodes or heavy deposits.
  15. An improper spark plug gap will cause a driveability problem. Gap spark plugs using a wire gauge gap tool.
  16. Determine the cause of fouling before replacing spark plugs.
  17. Monitor the Misfire Current Counters while driving the vehicle within the conditions that the misfire occurred. If a misfiring cylinder can be located, use the DTC P0300 diagnostic procedures for diagnosis. See DTC P0300 in «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-158433-S36149293242003092600000) in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
  18. Inspect for loose ignition coil grounds.
  19. Verify that the engine coolant temperature is not above 266°F (130°C). This condition causes PCM to operate in Engine Coolant Over Temperature - Fuel Disabled Mode. While in Engine Coolant Over Temperature - Fuel Disabled Mode, the PCM turns fuel OFF to 4 cylinders at a time to keep engine temperatures from reaching damaging levels. The driver may perceive this condition as a lack of power, miss or rough idle.
  20. Inspect for excessive crankshaft end play that will cause the CKP sensor reluctor wheel to move out of alignment with the CKP sensor. This could result in a no-start, a start and stall, or erratic performance.
  21. Visually and physically inspect vacuum hoses for splits, kinks, and proper connections and routing as shown on the underhood Vehicle Emission Control Information label.
  22. Inspect transmission Torque Converter Clutch (TCC) operation. See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. A TCC applying too soon can cause the engine to spark knock.

RESTRICTED EXHAUST

For dual exhaust systems a quick check of exhaust flow will help determine which side of the exhaust system is restricted. The side that has less exhaust flow is the side that will be suspect, and diagnosis should begin there. To diagnose exhaust system, refer to EXHAUST SYSTEM BACKPRESSURE under MECHANICAL INSPECTION under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.

INTERMITTENTS

Note. Intermittent is a DTC or symptom, with a condition that cannot be duplicated.

PRELIMINARY

Perform the Diagnostic System Check - Engine Controls before starting. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.

CONTROL MODULE POWER & GROUNDS, & COMPONENT POWER & GROUNDS

Poor power or ground connections can cause widely varying symptoms.

  1. Test all control module power circuits. Many vehicles have multiple circuits supplying power to the control module. Other components in the system may have separate power circuits that may also need to be tested. Inspect connections at the module or component connectors, fuses, and any intermediate connections between the power source and the module or component. A test light or a Digital Volt-Ohmmeter (DVOM) may indicate that voltage is present, but neither tests the ability of a circuit to carry sufficient current. Ensure that the circuit can carry the current necessary to operate the component. See «POWER DISTRIBUTION»(ref-154436-S34482561712003080900000) in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
  2. Test all control module ground and system ground circuits. The control module may have multiple ground circuits. Other components in the system may have separate grounds that may also need to be tested. Inspect grounds for clean and tight connections at the grounding point. Inspect the connections at the component and in splice packs, where applicable. Ensure that the circuit can carry the current necessary to operate the component. See «GROUND DISTRIBUTION»(ref-154436-S01937298952003080900000) in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

TEMPERATURE SENSITIVITY

  1. An intermittent condition may occur when a component or connection reaches normal operating temperature. The condition may occur only when the component or connection is cold, or only when the connection is hot.
  2. The following data may help to diagnose this type of intermittent condition: Freeze Frame/Failure Records. Scan tool snapshot. Vehicle data recorder.
  3. If the intermittent is related to heat, review the following data: High ambient temperatures. Underhood or engine generated heat. Circuit generated heat due to a poor connection, or high electrical load. Higher than normal load conditions, such as towing.
  4. If the intermittent is related to cold, review the following data: Low ambient temperatures. In extremely low temperatures, ice may form in a connection or component. Test for water intrusion. The condition only occurs on a cold start. The condition is not present after the vehicle warms up.
  5. Information from the customer may help to determine if the trouble follows a pattern that is temperature related.

INCORRECT PCM PROGRAMMING

  1. There are only a few situations when reprogramming a PCM is appropriate, such as the following: A new service PCM is installed. A PCM from another vehicle is installed. Revised software or calibration files have been released for this vehicle.
  2. Verify that the PCM contains the correct software or calibration. If incorrect programming is found, reprogram the PCM with the most current software or calibration. See «POWERTRAIN CONTROL MODULE»(ref-158433-S05468063462003092600000) under PROGRAMMING in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.

DUPLICATING FAILURE CONDITIONS

  1. If none of the previous tests are successful, attempt to duplicate or capture the failure conditions.
  2. Freeze Frame/Failure Records data, where applicable, contains the conditions that were present when the DTC set. Perform the following procedure: Review and record Freeze Frame/Failure Records data. Clear DTCs using scan tool. Turn ignition off and wait 15 seconds. Operate vehicle under the same conditions that were noted in Freeze Frame/Failure Records data, as closely as possible. The vehicle must also be operating within the Conditions for Running DTC. Monitor DTC Status for the DTC being tested. The scan tool will indicate Ran, when the enabling conditions have been satisfied long enough for the DTC to run. The scan tool will also indicate whether the DTC passed or failed.
  3. An alternate method is to drive vehicle with DVOM connected to a suspected circuit. An abnormal reading on the DVOM when problem occurs, may help you locate the problem.

VEHICLE DATA RECORDER

The Vehicle Data Recorder (J-42598) is connected to the Data Link Connector (DLC) and sent with customer. The vehicle data recorder captures data for later retrieval and analysis by the technician. Refer to vehicle data recorder user instructions for more information.

More articles — Engine Controls - Trouble Shooting - No Codes - 8.1L