INTRODUCTION
Note. Models may use a Powertrain Control Module (PCM) or Vehicle Control Module (VCM). The term PCM will be used in this article to describe all control modules.
Before diagnosing symptoms or intermittent faults, perform basic diagnostic procedures in the BASIC TESTING - 6.5L DIESEL article and self-diagnostic steps in the TESTS W/CODES - 6.5L article. Use this article to diagnose driveability problems if a current trouble code is not present or if not equipped with a self-diagnostic system.
Symptom checks are intended to direct technician to malfunctioning component(s) for further diagnosis. A symptom should lead to a specific component or system test, or an adjustment specification. Use intermittent test procedures to locate driveability problems not occurring when vehicle is being tested.
Note. For specific testing, see SYSTEM/COMPONENT TESTS article. For specifications, see ADJUSTMENTS - 6.5L DIESEL article or SPECIFICATIONS - 6.5L DIESEL article.
Note. SERVICE ENGINE SOON light, located on instrument cluster, is also referred to as the Malfunction Indicator Light (MIL).
PRELIMINARY CHECKS
- Verify the on-vehicle diagnostics are working by performing ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in the «BASIC TESTING - 6.5L DIESEL»(/chevrolet/chevy-van-g3500/1996-1998/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-65l-diesel-g-series) article.
- Ensure PCM and MIL function properly.
- Ensure no trouble codes (except intermittent) are stored.
- Ensure fuel control system operates properly. See the «BASIC TESTING - 6.5L DIESEL»(/chevrolet/chevy-van-g3500/1996-1998/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-65l-diesel-g-series) article.
- Perform fuel system pressure test.
- Visually inspect all systems.
After all checks have been performed, verify customer complaint and locate correct symptom. Check items indicated under that symptom. Not all items listed under each symptom apply to all models and systems. These procedures normally recommend testing of specific system/component, such as EGR, TCC, etc. See the SYSTEM/COMPONENT TESTS article for test procedures.
Possible Cause
No voltage to fuel shut-off solenoid.
Correction
Check electrical connections.
Restricted air filter.
Check and/or replace air filter.
Faulty glow plugs, relay or PCM.
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 the SYSTEM/COMPONENT TESTS article.
Incorrect or contaminated fuel.
Remove and replace fuel.
Restriction in turbocharger inlet duct (if equipped).
Remove restrictions.
Incorrect pump timing.
See the TESTS W/CODES - 6.5L article.
Incorrect slow idle.
See the TESTS W/CODES - 6.5L article.
Faulty fast idle solenoid.
Replace solenoid. See the SYSTEM/COMPONENT TESTS article.
Plugged fuel return system.
Remove restrictions.
Glow plugs turn off too soon.
Check glow plug system. See SYSTEM/COMPONENT TESTS article.
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 REMOVE/INSTALL/OVERHAUL article.
Fuel shut-off solenoid closes in RUN position.
Check solenoid operation. See SYSTEM/COMPONENT TESTS article.
TCC stuck on.
Check brake switch and PCM control.
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 SYSTEM/COMPONENT TESTS article.
Improper or contaminated fuel.
Remove and replace fuel.
Uneven fuel distribution.
Check fuel delivery system.
Incorrect pump timing.
See the TESTS W/CODES - 6.5L article.
Restricted air filter.
Check and/or replace air filter.
Air in injection lines to nozzles.
Check fittings on lines.
Faulty nozzle.
Replace nozzle. See SYSTEM/COMPONENT TESTS article.
Improperly installed high pressure lines.
Remove lines, and reinstall properly.
Misrouted or kinked vacuum lines.
Check lines, and reinstall properly.
Faulty EGR operation
Check EGR system.
Faulty charging system.
Check alternator output.
Faulty PCM operation.
See the TESTS W/CODES - 6.5L article.
Faulty TCC or shift points.
Check transmission operation.
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.
Faulty PCM operation.
See the TESTS W/CODES - 6.5L article.
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.
Faulty EGR operation.
Check EGR system.
Worn camshaft or valves. Repair as necessary
Check compression and valve lift.
Nozzle or glow plug compression leaks.
Check fittings, and replace as required.
Plugged nozzle.
Remove restriction and/or replace nozzle.
Worn or damaged turbocharger turbine wheel, shaft or compressor wheel (if equipped).
Repair or replace turbocharger assembly.
Faulty TCC or shift points.
Check transmission operation.
Air in fuel system.
Check fuel delivery system for leaks.
Air in high pressure lines.
Check fittings for leaks.
Incorrect pump timing.
See the TESTS W/CODES - 6.5L article.
Nozzle sticking in open position.
Inspect and/or replace nozzle.
Low nozzle opening pressure.
Check nozzle operation. See SYSTEM/COMPONENT TESTS article.
Excessive oil entering combustion chamber.
Repair internal engine problem.
Faulty ECT sensor.
Check sensor operation. See SYSTEM/COMPONENT TESTS article.
Incorrect pump timing.
See the TESTS W/CODES - 6.5L article.
Incorrect pump pressure.
Check pump for internal leaks.
Defective injection pump.
Replace injection pump. See SYSTEM/COMPONENT TESTS article.
Engine coolant temp sensor reading is 5 degrees greater or less than ambient temperature on a cold engine.
Check for high resistance in sensor circuit or sensor.
Injection pump fuel shut-off solenoid does not return to off position.
Check solenoid operation. See SYSTEM/COMPONENT TESTS article.
SYMPTOMS
To trouble shoot following symptoms, refer to appropriate number under PROBABLE CAUSES .
Engine Lacks Power
Check probable causes No. 1, 3, 4, 6-11 and 16-21.
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.
Noisy Operation
Check probable causes No. 1-8, 11-12 and 19-20.
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.
PROBABLE CAUSES
- Clogged air filter element.
- Obstructed air intake duct to turbo compressor.
- Obstructed air outlet duct from compressor to intake manifold.
- Obstructed intake manifold.
- Air leak in duct from air cleaner to compressor.
- Air leak in duct from compressor to intake manifold.
- Air leak at intake manifold-to-engine joint.
- Obstruction in exhaust manifold.
- Obstruction in exhaust system.
- Gas leak in exhaust manifold-to-engine joint.
- Gas leak in turbine inlet-to-exhaust manifold joint.
- Gas leak in ducts after turbine outlet.
- Obstructed turbocharger oil drain line.
- Obstructed engine crankcase ventilation.
- Turbocharger center housing sludged or coked.
- Engine camshaft timing incorrect.
- Worn engine piston rings or liners (blow-by).
- Internal engine problems (valves, pistons).
- Dirt caked on compressor wheel and/or diffused vanes.
- Damaged turbocharger.
- Wastegate stuck open.
INTERMITTENT PROBLEM DIAGNOSIS
Intermittent problem diagnosis requires duplication of circuit or component failure in order to identify problem. These procedures may lead to computer recording a trouble code which may help diagnosis.
If problem vehicle does not produce a trouble code, use a scan tool or DVOM to monitor voltage or resistance values while attempting to reproduce conditions which will create an intermittent problem. A change in status on scan tool or DVOM indicates a problem has been located.
When monitoring voltage, ensure ignition switch is in ON position or engine is running. When monitoring resistance (ohms), ensure ignition switch is in OFF position or negative battery cable is disconnected. A status change on scan tool or DVOM while performing TEST PROCEDURES indicates area of problem.
Intermittent Simulation
Use following methods to reproduce conditions causing intermittent.
- Apply light vibration to components.
- Heat component.
- Wiggle or bend wiring harness.
- Spray component with water.
- Remove/apply vacuum supply source.
Monitor circuit/component voltage or resistance while attempting to simulate intermittent. If vehicle is running, monitor for trouble codes. Use test results to identify faulty component or circuit.
Symptom Definition
Malfunction Indicator Light (MIL) comes on but does not stay on. A stored trouble code may or may not exist.
Possible Causes & Corrections
Use following procedures to determine possible causes of intermittent Malfunction Indicator Light (MIL) operation.
- 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.
- Check for poor connection from ignition coil to ground or arcing at spark plug wires or plugs.
- Check wire from Malfunction Indicator Light (MIL) to PCM for short to ground.
- Check wire from Data Link Connector (DLC) test terminal for intermittent short to ground.
- Check for poor connections in PCM ground terminals.
- Check for electrical system interference caused by defective relay, PCM-driven solenoid or switch, which may cause sharp electrical surge. This type of problem will normally occur when faulty component is operated.
- Check for aftermarket parts which may not have been produced to manufacturers' specifications. Solenoids without original -equipment diodes for circuit protection or voltage regulator using transistors instead of silicone-chip circuitry may cause voltage surges (up to 300 volts) in PCM wiring, causing temporary PCM shutdown. PCM shutdown is a normal response to system overvoltage (over 16 volts on most models). PCM repowers when condition ceases to exist. A rapid shutdown and repower could cause a flickering Malfunction Indicator Light (MIL) with no codes set in memory.
- Check for improper installation of electrical accessories such as auxiliary lights or 2-way radios.
- Ensure EST wires are kept away from spark plug wires, distributor wires, distributor housing, ignition coil and generator. Ensure ground wire from PCM to distributor or ignition module is connected to a good ground.
- Check for intermittent short to ground on terminal "B" (diagnostic enable) of Data Link Connector (DLC) or in Malfunction Indicator Light (MIL) circuit.
- On vehicles not equipped with a driver information center, use scan tester to check for intermittent wiring problem. See SCAN TESTER USAGE in the «TESTS W/CODES - 6.5L»(/chevrolet/chevy-van-g3500/1996-1998/remont/testing-diagnostics/#engine-controls-tests-wcodes-65l-diesel-g-series) article.