Engine Controls - Basic Diagnostic Procedures - 4.3L: Other Chevrolet Silverado 1500 HD

Cylinder Compression Pressure

Check engine mechanical condition with compression gauge, vacuum gauge, or engine analyzer. See engine analyzer manual for specific instructions. For compression specifications, see ENGINE COMPRESSION SPECIFICATIONS table. Install and tighten spark plugs to 11 ft. lbs. (15 N.m).

ENGINE COMPRESSION SPECIFICATIONS

Cylinder Combustion Pressure Leakage

1. Disconnect negative battery cable. Remove spark plugs. Install Cylinder Head Leakdown Tester (J-35667 A). Measure each cylinder on compression stroke, with both valves closed.
2. Apply air pressure to cylinder leakdown tester. Record cylinder leakage readings for each cylinder. Any cylinder with 25 percent leakage or more requires service.
3. Inspect following primary areas in order to properly diagnose a leaking cylinder. If air is heard from intake or exhaust system, remove valve rocker arm cover of suspect cylinder head. Ensure that both valves are closed. Inspect cylinder head for a broken valve spring or remove and inspect suspect cylinder head. If air is heard from crankcase system at crankcase oil filler tube, remove piston from suspect cylinder. Inspect piston and connecting rod assembly. Inspect engine block. If bubbles are observed in radiator, remove and inspect both cylinder heads. Inspect engine block.
4. After performing test, remove leakdown tester. Install spark plugs and reconnect negative battery cable.

Exhaust System Backpressure

Before replacing any components, check exhaust system for restrictions. Use vacuum gauge or low pressure (0-5 psi) gauge to check exhaust system.

If vacuum gauge is used, connect vacuum gauge hose to intake manifold vacuum port and start engine. Observe vacuum gauge. Partially open throttle and hold steady. If vacuum gauge reading slowly drops after stabilizing, exhaust system should be checked for restriction. If using low pressure gauge, connect gauge in following manner

1. Check At Oxygen Sensor - Remove oxygen sensor. Install backpressure tester in place of oxygen sensor. After test is completed, coat oxygen sensor threads with anti-seize compound before installation.

Preliminary Checks

Before performing following tests, check battery condition, engine cranking speed and for adequate fuel in tank. Perform diagnostic system check following any repairs. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.3L SIERRA & SILVERADO article.

1. Perform diagnostic system check. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-158208-S20709970632003091700000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.3L SIERRA & SILVERADO article. After performing diagnostic system check, go to next step.
2. Using scan tool, check for DTCs. If DTCs P0230, P0335, P0336, P0601, P0602, P0604, P1626, P1631 or P1683 are set, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-158208-S06912544392003091700000) in SELF-DIAGNOSTICS - 4.3L SIERRA & SILVERADO article. If DTCs are not set, go to next step.
3. Does scan tool display any Body Control Module (BCM) or Vehicle Theft Deterrent (VTD) DTCs? If yes, diagnose affected DTCs. See appropriate BODY CONTROL MODULES or ANTI-THEFT SYSTEMS article in ACCESSORIES & EQUIPMENT. If no, go to next step.
4. Using a test light connected to ground, probe both sides of the following fuses: ECM 1, INJ "A" and INJ "B". Does the test light illuminate on at least one side of all of the fuses? If yes, go to next step. If no, go to «IGNITION RELAY»(ref-153194-S38446411412003041400000) under MODULES, MOTORS, RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING - 4.3L SIERRA & SILVERADO article.
5. Attempt to start engine. Observe Engine Speed parameter with a scan tool, while engine is cranking. Does engine speed increment? If yes, go to next step. If no, go to «DISTRIBUTOR IGNITION SYSTEM»(ref-152743-S42313966012003022400000) under IGNITION SYSTEMS.
6. Monitor ignition 1 signal voltage parameter with a scan tool. (Scheme 2) Is ignition 1 signal voltage parameter at battery voltage? If yes, go to next step. If no, go to step 11.
7. Command fuel pump on with a scan tool. Does fuel pump turn on? If yes, go to next step. If no, go to «FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS»(ref-153194-S16761577012003041400000) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 4.3L SIERRA & SILVERADO article.
8. Turn ignition off. Disconnect a spark plug wire. Install Spark Tester (J-26792) to spark plug wire. Attempt to start engine. Does spark tester spark? If yes, go to next step. If no, go to «DISTRIBUTOR IGNITION SYSTEM»(ref-152743-S42313966012003022400000) under IGNITION SYSTEMS.
9. Turn ignition off. Install Fuel Pressure Gauge (J-34730-1A). Turn ignition on, with engine off. Command fuel pump on with a scan tool. Is fuel pressure within 55-62 psi (379-427 kPa ) while fuel pump is operating? If yes, go to next step. If no, go to «FUEL SYSTEMS»(ref-152743-S00302466912003022400000).
10. Inspect for collapsed air intake duct, restricted air filter element, fouled spark plugs, engine mechanical problem or restricted exhaust system. Check if ECT sensor is NOT close to actual engine temperature. Compare MAP/BARO parameters to another vehicle. The parameters should be close in value. Check if TP sensor is stuck in range. Repair as necessary. After repairs, go to step 14.
11. Test ignition 1 signal voltage circuit for an open or for a short to ground. (Scheme 2) Replace fuse, if necessary. Did you find and correct condition? If yes, go to step 14. If no, go to next step.
12. Inspect for poor connections at harness connector of PCM. Did you find and correct condition? If yes, go to step 14. If no, go to next step.
13. Replace PCM. See appropriate REMOVAL & INSTALLATION article. After replacing PCM, go to next step.
14. Clear DTCs with a scan tool. Turn ignition off for 30 seconds. Attempt to start engine. Does engine start and continue to run? If yes, go to next step. If no, go to step 2.
15. Observe Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? If yes, diagnose affected DTC(s). See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-158208-S06912544392003091700000) in SELF-DIAGNOSTICS - 4.3L SIERRA & SILVERADO article. If no DTCs are set, system okay.

FUEL SYSTEM PRESSURE RELEASE

Disconnect negative battery terminal. Loosen fuel filler cap to release fuel tank vapor pressure. Connect Fuel Pressure Gauge (J-34730-1A) to fuel pressure test port. Wrap a shop towel around fitting while connecting gauge to avoid spillage. Install gauge bleed hose into an approved gasoline container. Open valve on gauge to bleed system pressure. Fuel connections are now safe for servicing. Drain any fuel remaining in gauge into an approved gasoline container.

IGNITION SYSTEMS

Note. For additional ignition system and component diagnosis, see IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - 4.3L SIERRA & SILVERADO article.

CAMSHAFT POSITION SENSOR

For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.3L SIERRA & SILVERADO article.

CRANKSHAFT POSITION SENSOR

For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.3L SIERRA & SILVERADO article.

Scheme 1

Scheme 2

IDLE SPEED & IGNITION TIMING

Idle speed and ignition timing are controlled by PCM. Incorrect idle speed are normally caused by dirty throttle plate or vacuum leaks. Ensure all vacuum components are functioning properly.

SIERRA - 1500

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SILVERADO - 1500

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.