Engine Controls - Tests W/o Codes: Other Chevrolet Pickup K1500

HOW TO USE THIS SECTION

Use this portion of article only AFTER performing these checks

1. Ensure on-vehicle diagnostics work (if equipped). Perform DIAGNOSTIC CIRCUIT CHECK in BASIC TESTING article in this section.
2. Ensure ECM and SERVICE ENGINE SOON light function properly.
3. Ensure no trouble codes, except intermittent ones, are stored.
4. Ensure fuel control system operates properly. Perform FIELD SERVICE MODE CHECK in BASIC TESTING article in the ENGINE PERFORMANCE Section.
5. Perform fuel system pressure test.
6. Visually inspect all systems.

After performing these checks, verify customer complaint, and locate correct symptom from among those listed in this article. Not all items listed under each symptom apply to all models and systems. These procedures normally recommend testing of a system or component on vehicle, such as EGR, EST, TCC, etc. See I - SYS/COMP TESTS article in this section for specific testing procedures.

Note. If ECM displays data but engine fails to start, see NO-START DIAGNOSIS in BASIC TESTING article in the ENGINE PERFORMANCE Section.

Possible Causes & Corrections

1. Check fuel pump relay. Connect test light between fuel pump test terminal and ground or between fuel pump connector and ground. Turn ignition on. Light should illuminate for 2 seconds. If not, check fuel pump relay. See RELAYS in I - SYS/COMP TESTS article in this section. For location of fuel pump test connector, see COMPONENT LOCATIONS in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
2. Check for poor fuel quality or water-contaminated fuel.
3. Ensure TPS does not stick or bind.
4. Check EGR valve operation.
5. Check for a leaking injector. Disconnect injector electrical connector at injector. Crank engine, and watch for fuel leakage.
6. Ensure coolant sensor circuit resistance or coolant sensor resistance is not too high. See SENSOR RANGE CHARTS article in this section or CODE 15 chart in appropriate TESTS W/CODES article in the ENGINE PERFORMANCE Section.
7. Check ignition system for a worn distributor shaft, bare or shorted wires, incorrect pick-up coil resistance, loose ignition coil ground or moisture in distributor cap. Using Spark Tester (ST-125), check for adequate spark.
8. Check for shorts by misting plug wires with water.
9. Remove spark plugs. Check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits.
10. Check for correct fuel pressure at all speeds.
11. Check for a faulty in-tank fuel pump check valve. A faulty check valve allows fuel in lines to drain back to tank after engine is stopped.
12. Ensure correct PROM is installed in vehicle. Check with dealer for latest application information.
13. Check for restricted exhaust system.

1. Ensure hot air tube is connected to air cleaner.
2. Check thermostatic air cleaner for proper operation.
3. Check Idle Air Control (IAC) system for proper operation.
4. Check PCV valve for proper operation.
5. Unplug MAP sensor. ECM substitutes a default value for sensor signal. If stall condition is eliminated, replace sensor.
6. Check EGR system for proper operation.
7. If stall occurs when air conditioner is turned on, check for air conditioner clutch signal to ECM terminal. Voltage at A/C terminal of ECM should be battery voltage when air conditioner compressor clutch is engaged. A high voltage surge due to a shorted compressor clutch diode could cause ECM shutdown.
8. Check for an overcharged A/C system.
9. Check for plugged or restricted fuel lines.
10. If engine starts but then immediately stalls, open distributor by-pass circuit. If engine now starts and runs okay, replace distributor pick-up coil.
11. Using Spark Tester (ST-125), check for a weak spark from ignition coil.

1. Visually check vacuum hoses for splits, kinks and improper connections, as shown on Vehicle Emission Control Information label.
2. Check ignition wires for cracking, hardness and improper connections at both distributor cap and spark plugs.
3. Check wires for pinches, cuts and improper connections.
4. Ensure fuel pressure is correct in all speed ranges. Also check for poor fuel quality or water-contaminated fuel.
5. Check for fouled spark plugs.
6. Ensure correct PROM is installed in vehicle. Check with dealer for latest application information.
7. Ensure TPS does not bind or stick.
8. Ensure initial ignition timing is properly set.
9. Ensure ECM-controlled idle speed is correct.
10. Check EGR system for proper operation.
11. Disconnect fuel injector electrical connectors. Crank engine, and check for injector leaks.
12. Check for an open in HEI ground circuit.
13. Check canister purge system for proper operation.
14. Check charging system output. Repair charging system if voltage is less than 9 volts or more than 16 volts.

1. Check thermostatic air cleaner damper door for proper operation.
2. Ensure park/neutral switch is properly adjusted.
3. Check for intermittent open or short to ground in Torque Converter Clutch (TCC) or HEI by-pass circuits.
4. Check canister purge system for proper operation.
5. Check ESC system for proper operation.
6. Check EGR system for proper operation.
7. Ensure initial ignition timing is properly set.
8. Using Spark Tester (ST-125), check for adequate spark output.
9. Check O2 sensor for lead or RTV sealant contamination. Such contamination causes a false high voltage signal to ECM, which responds by leaning air/fuel ratio.
10. Check in-line fuel filter. Replace if dirty or clogged.
11. Check fuel for water contamination. Ensure fuel system pressure is correct at all engine speeds.
12. Remove spark plugs, and check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits. Also check condition of distributor cap, rotor and spark plug wires.
13. Check A/C for excessive charge.
14. Check for restricted exhaust system.

1. Check air filter and fuel filter. Replace if necessary. Check for incorrect fuel pressure.
2. Check injector wires for short to ground at air cleaner.
3. Check thermostatic air cleaner damper door for proper operation.
4. Ensure initial ignition timing is properly set.
5. Check TCC system for proper operation.
6. Check ECM grounds.
7. Check ESC system for excessive retard.
8. Check EST system for proper operation.
9. Ensure EGR valve is not always open.
10. Check exhaust system for restrictions, such as a damaged or collapsed pipe, muffler or catalytic converter. See EXHAUST SYSTEM BACKPRESSURE under MECHANICAL INSPECTION in BASIC TESTING article in this section.
11. Check charging system output. Repair charging system if voltage is less than 9 volts or more than 16 volts.
12. Check MAP sensor output.
13. Using Spark Tester (ST-125), check for available secondary voltage.
14. Check engine valve timing and compression.
15. Check engine for a worn camshaft.

1. Ensure EGR valve is not always open.
2. Check for proper valve timing.
3. Check for engine vacuum leaks. Ensure engine is tuned to specifications.
4. Check for faulty air injection diverter valve or check valve.
5. Check engine for sticking or leaking valves.
6. Check for fuel or water in vacuum hose to MAP sensor. Also check for restricted hose.
7. Using Spark Tester (ST-125), check available output voltage of ignition coil.
8. Check for crossfire between spark plugs, distributor cap and spark plug wires.
9. Check for an intermittent ignition system problem.
10. Check for erratic spark timing or distributor reference (RPM) signal.
11. Ensure initial ignition timing is properly set.

1. Check ignition wires for short or faulty insulation.
2. Check distributor cap for moisture, dust or cracks. Finely mist spark plug wires with water to check for shorts.
3. Connect Spark Tester (ST-125) to spark plug, and check for adequate spark.
4. Check ignition system for faulty grounds.
5. Ensure EST wiring harness is not routed too close to wiring. EST wiring harness routed too close to wiring may cause induced voltage signals.
6. Check ignition coil connections.
7. Remove spark plugs, and check for incorrect heat range, wear, cracks, wetness, improper gap or heavy deposits.
8. Check for poor or contaminated fuel.
9. Check for improper fuel pressure.
10. Ensure EGR valve does not stick open.
11. Check ECM for proper ground circuits.
12. Ensure TPS does not stick or bind. TPS voltage should be less than 1.25 volts at idle.
13. Check for proper pick-up coil (HEI distributor) resistance.
14. Check for restricted exhaust system. See EXHAUST SYSTEM BACKPRESSURE under MECHANICAL INSPECTION in BASIC TESTING article in this section.
15. Check for bent push rods, broken valve springs or worn camshaft lobes.

Misfire Isolation

1. Start engine. Disconnect IAC motor. Using insulated pliers, remove one spark plug wire from a spark plug, and ground it against engine.
2. Note engine RPM as wire is grounded. Reconnect spark plug wire. Repeat procedure for all cylinders. Stop engine, and reconnect IAC motor.
3. If engine speed dropped equally (within 50 RPM) on all cylinders, refer to ROUGH, UNSTABLE OR INCORRECT IDLE symptom. If there was no engine RPM drop or no excessive variation on one or more cylinders, check spark on respective cylinder(s).

1. Ensure throttle linkage and/or TPS do not stick or bind.
2. Ensure initial ignition timing is properly set.
3. Check engine idle speed (both base and ECM idle).
4. Check Idle Air Control (IAC) system. Check for foreign material in IAC bore. See DIAGNOSTIC AIDS in CODE 35 chart in appropriate TESTS W/CODES article in the ENGINE PERFORMANCE Section.
5. Check EGR system for proper operation.
6. Check park/neutral switch circuit. Ensure park/neutral switch is properly adjusted.
7. Check power steering pressure switch circuit.
8. Check exhaust system for restrictions, such as a damaged or collapsed pipe, muffler or catalytic converter. See EXHAUST SYSTEM BACKPRESSURE under MECHANICAL INSPECTION in BASIC TESTING article in this section.
9. If rough idle occurs only when engine is hot, check PCV valve for proper operation. Check evaporative emission control system. Check for proper spark plug gap and engine compression.

1. Problem is most likely in Idle Air Control (IAC) system. See DIAGNOSTIC AIDS in CODE 35 chart in appropriate TESTS W/CODES article in this section.
2. Check EGR system.
3. Check park/neutral switch.
4. Disconnect MAP sensor. If condition is corrected, replace sensor.

1. Check thermostatic air cleaner damper door for proper operation. Also check for a clogged air filter.
2. Check cooling system thermostat for proper heat range and operation.
3. Check coolant sensor for shift in calibration. See COOLANT TEMPERATURE RESISTANCE VALUES table in SENSOR RANGE CHARTS article in this section.
4. Ensure speedometer is properly calibrated.
5. Check engine compression.
6. Check for dragging brakes.
7. Ensure A/C is not always on.
8. Ensure initial ignition timing is properly set. Check EST and ESC for proper operation.
9. Check TCC for proper operation.
10. Ensure air pump output shifts to catalytic converter upon signal from TVS. Check for faulty electrical and/or vacuum circuits.
11. Check exhaust system for restrictions, such as a damaged or collapsed pipe, muffler or catalytic converter. See EXHAUST SYSTEM BACKPRESSURE under MECHANICAL INSPECTION in BASIC TESTING article in this section.
12. Check O2 sensor for silicone or lead contamination.
13. Remove spark plugs, and check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits.

1. Check for binding throttle linkage.
2. Check for leaking injectors.
3. Check IAC system. See DIAGNOSTIC AIDS in CODE 35 chart in appropriate TESTS W/CODES article in the ENGINE PERFORMANCE Section.
4. Check engine for overheating.

1. Check for obvious overheating problems.
2. Ensure initial timing is correct.
3. Check TPS adjustment and operation.
4. Check fuel system for low pressure or volume. Also check for induction air leaks.
5. Ensure ESC system is operating properly.
6. Ensure EGR valve is not always open.
7. Ensure TCC system is operating properly.
8. Remove carbon from engine with top engine cleaner.
9. If excessive carbon exists in combustion chamber, check for excessive oil burning due to leaking valve guide seals.
10. Check for incorrect basic engine parts such as camshaft, cylinder heads and pistons.
11. Ensure correct PROM is installed in vehicle. Check with dealer for latest application information.

1. Check for lead contamination of catalytic converter. Check for removal/tampering at restrictor in fuel filler neck.
2. Ensure air is not being diverted to exhaust manifold and is being diverted to catalytic converter during normal engine operation.
3. If emission test shows excessive carbon monoxide (CO) and hydrocarbons (HC) emissions and vehicle emits odor, check all systems and components which could cause engine to run rich. See DIAGNOSTIC AIDS in CODE 45 chart in appropriate TESTS W/CODES article in this section.
4. If emission test shows excessive oxides of nitrogen (NOx) emissions, check all systems and components which could cause engine to run lean or too hot. See DIAGNOSTIC AIDS in CODE 44 chart in appropriate TESTS W/CODES article in the ENGINE PERFORMANCE Section.

Possible Cause

No voltage to fuel solenoid.

Correction

Check electrical connections.

Restricted air filter.

Check and/or replace air filter.

Faulty glow plugs or glow plug controls.

Check and/or replace glow plugs or controls.

Plugged fuel return system.

Remove restrictions.

No fuel to nozzles.

Inspect fuel delivery system.

No fuel to injection pump.

Inspect fuel delivery system.

Clogged fuel tank filter.

Replace filter. See I - SYS/COMP TESTS article in this section.

Incorrect or contaminated fuel.

Remove and replace fuel.

Incorrect pump timing.

Reset pump timing. See I - SYS/COMP TESTS article in this section.

Incorrect slow idle adjustment.

Reset idle adjustment. See ADJUSTMENTS article in this section.

Faulty fast idle solenoid.

Replace solenoid. See I - SYS/COMP TESTS article in this section.

Plugged fuel return system.

Remove restrictions.

Glow plugs turn off too soon.

Check glow plug system. See I - SYS/COMP TESTS article in this section.

Incorrect pump timing.

Check and reset timing. See ADJUSTMENTS article in this section.

Limited fuel to injection pump.

Check fuel delivery system.

Air in injection lines to nozzles.

Check line fittings.

Incorrect or contaminated fuel.

Remove and replace fuel.

Faulty injection pump.

Replace pump. See N - REMOVE/INSTALL/OHAUL article in this section.

Fuel solenoid closes in RUN position.

Check solenoid operation. See I - SYS/COMP TESTS article in this section.

Incorrect slow idle adjustment.

Reset slow idle adjustment. See ADJUSTMENTS article in this section.

Leaking injection line.

Check fittings and/or replace line.

Plugged fuel return line.

Remove restrictions.

Air in lines to nozzles.

Check line fittings.

Air in injection pump.

Check pump fittings and pump operation.

Faulty nozzle.

Replace nozzle. See I - SYS/COMP TESTS article in this section.

Improper or contaminated fuel.

Remove and replace fuel.

Uneven fuel distribution.

Check fuel delivery system.

Incorrect pump timing.

Adjust pump timing. See ADJUSTMENTS article in this section.

Restricted air filter.

Check and/or replace air filter.

Air in injection lines to nozzles.

Check fittings on lines.

Faulty nozzle.

Replace nozzle. See I - SYS/COMP TESTS article in this section.

Improperly installed high pressure lines.

Remove lines, and reinstall properly.

Plugged fuel filter.

Remove restrictions and/or replace filter.

Incorrect pump timing.

Adjust pump timing. See ADJUSTMENTS article in this section.

Incorrect or contaminated fuel.

Remove and replace fuel.

Linkage binding or misadjusted.

Remove binding and readjust linkage.

Restricted air filter.

Check and/or replace air filter.

Defective injection pump.

Replace injection pump. See I - SYS/COMP TESTS article in this section.

Loose or broken fuel line or connection.

Check all fuel line fittings, and correct as necessary.

Internal seal leak in injection pump.

Remove and replace injection pump.

Restricted air intake.

Remove restrictions.

Plugged fuel filter.

Remove restriction and/or replace filter.

Improper throttle linkage adjustment.

Adjust linkage.

Improper fuel return system.

Check fuel return system.

Restricted tank-to-pump fuel supply.

Check fuel delivery system.

Incorrect or contaminated fuel.

Remove and replace fuel.

Restricted fuel tank filter.

Replace filter.

Nozzle or glow plug compression leaks.

Check fittings, and replace as required.

Plugged nozzle.

Remove restriction and/or replace nozzle.

Air in fuel system.

Check fuel delivery system for leaks.

Air in high pressure lines.

Check fittings for leaks.

Nozzle sticking in open position.

Inspect and/or replace nozzle.

Low nozzle opening pressure.

Check nozzle operation. See I - SYS/COMP TESTS article in this section.

Incorrect pump timing.

Adjust pump timing. See ADJUSTMENTS article in this section.

Incorrect pump housing pressure.

Check pump for internal leaks.

Defective injection pump.

Replace injection pump. See I - SYS/COMP TESTS article in this section.

Injection pump fuel solenoid does not return to off position.

Check solenoid operation. See I - SYS/COMP TESTS article in this section.

Engine Lacks Power

Check probable causes No. 1, 3, 4, 6-11 and 16-20.

Black Smoke

Check probable causes No. 2-4, 6-11 and 16-20.

Blue Smoke

Check probable causes No. 2, 6-8, 13-15 and 17-20.

Excessive Oil Consumption

Check probable causes No. 2, 6-8, 13-15 and 17-20.

Cyclic Sound From Turbocharger

Check probable causes No. 2, 19 and 20.

Oil Leak At Turbine Seal

Check probable causes No. 13-15 and 17-20.

Oil Leak At Compressor Seal

Check probable causes No. 2, 8-11, 13-15 and 17-20.

1)

Clogged air filter element.

2)

Obstructed air intake duct to turbo compressor.

3)

Obstructed air outlet duct from compressor to intake manifold.

4)

Obstructed intake manifold.

5)

Air leak in duct from air cleaner to compressor.

6)

Air leak in duct from compressor to intake manifold.

7)

Air leak at intake manifold-to-engine joint.

8)

Obstruction in exhaust manifold.

9)

Obstruction in exhaust system.

10)

Gas leak in exhaust manifold-to-engine joint.

11)

Gas leak in turbine inlet-to-exhaust manifold joint.

12)

Gas leak in ducts after turbine outlet.

13)

Obstructed turbocharger oil drain line.

14)

Obstructed engine crankcase ventilation.

15)

Turbocharger center housing sludged or coked.

16)

Engine camshaft timing incorrect.

17)

Worn engine piston rings or liners (blow-by).

18)

Internal engine problems (valves, pistons).

19)

Dirt caked on compressor wheel and/or diffused vanes.

20)

Damaged turbocharger.

Intermittent Simulation

Following methods may reproduce conditions which create an intermittent fault so fault may be identified during testing

1. Applying light vibration to components.
2. Heating a component.
3. Wiggling or bending a wiring harness.
4. Applying humidity to a component.
5. Removing or applying a vacuum supply source.

Monitor circuit/component voltage or resistance while

attempting to simulate intermittent. If vehicle is running, monitor for self-diagnostic codes. Use results of these tests to identify a faulty component or an area which should be closely checked for problem.

To determine possible causes of an intermittent SERVICE ENGINE SOON light operation

1. Check for poor mating of one connector to another. Terminals may not be fully seated. Check for improperly formed or damaged terminals. Check wire-to-terminal connections.
2. Check for poor connection from ignition coil to ground or arcing at spark plug wires or plugs.
3. Check wire from SERVICE ENGINE SOON light to ECM for short to ground.
4. Check wire from ALDL "test" terminal for intermittent short to ground.
5. Check for poor connections in ECM ground terminals.
6. Check for loss of trouble code memory. To check code, disconnect TPS, and run engine at idle until SERVICE ENGINE SOON light comes on. Code 22 should be stored and retained in memory when ignition is turned off. If not, ECM is faulty.
7. Check for electrical system interference caused by a defective relay or an ECM-driven solenoid or switch which may cause a sharp electrical surge. This type of problem will normally occur when faulty component is operated.
8. Check for aftermarket parts which may not have been produced to manufacturers' specifications. Solenoids without original- equipment diodes for circuit protection and HEI-EST module or voltage regulator using transistors instead of silicone-chip circuitry may possibly cause voltage surges (up to 300 volts) in ECM wiring, causing temporary ECM shutdown. ECM shutdown is a normal response to system overvoltage (over 16 volts on most models). ECM repowers when condition ceases to exist. A rapid shutdown and repower could cause a flickering SERVICE ENGINE SOON light with no codes set in memory.
9. Check for improper installation of electrical accessories such as auxiliary lights or 2-way radios.
10. Ensure EST wires are kept away from spark plug wires, distributor wires, distributor housing, ignition coil and generator. Ensure ground wire from ECM to distributor or ignition module is connected to a good ground.
11. Check for intermittent short to ground on terminal "B" (diagnostic enable) of ALDL or in SERVICE ENGINE SOON light circuit.
12. On vehicles not equipped with a driver information center, use scan tester to check for intermittent wiring problem. See SCAN TESTER USAGE in appropriate TESTS W/CODES article in this section.