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Wiring diagrams Section: Testing & Diagnostics

Engine Controls - Basic Diagnostic Procedures - 4.8L, 5.3L & 6.0L - Flex Fuel & Gasoline Engines: Overview
Engine Controls - Basic Diagnostic Procedures - 4.8L, 5.3L & 6.0L - Flex Fuel & Gasoline Engines: Diagnosis
Engine Controls - Basic Diagnostic Procedures - 4.8L, 5.3L & 6.0L - Flex Fuel & Gasoline Engines: Other

Engine Controls - Strategy Based Engine Diagnosis

All sections

Engine Controls - System & Component Testing - 6.0L W/bifuel & Cng: Other Chevrolet Silverado 1500 HD

Testing & Diagnostics 1 illustration ~2053 words

COMPUTERIZED ENGINE CONTROLS

Note. For component locations, see COMPONENT LOCATIONS .

FUEL INJECTOR CONTROL MODULE & POWERTRAIN CONTROL MODULE

Note. To identify circuits referenced in the following ground and power tests, see WIRING DIAGRAMS or see scheme 3- see scheme 16.

Ground Circuits

Check Fuel Injector Control Module (FICM) and PCM connectors for corroded or loose connections. Repair as necessary. Disconnect FICM or PCM connectors. Using a DVOM, measure resistance between negative battery terminal and ground terminals at FICM or PCM harness connector. If resistance is more than 5 ohms, repair open in affected ground circuit. If resistance is 5 ohms or less, ground circuits are okay.

Power Circuits

Check FICM or PCM connectors for corroded or loose connections. Repair as necessary. Disconnect FICM or PCM connectors. Using a DVOM, check for battery voltage between chassis ground and continuous power terminal(s) at FICM or PCM harness connector(s). If battery voltage is present, go to next step. If battery voltage is not present, check for open fuse or fusible link. If fuse or fusible link is okay, check for open in wire between FICM or PCM terminal and power source.
Turn ignition switch to RUN position. Using DVOM, check for battery voltage between chassis ground and ignition power terminals at FICM or PCM harness connector(s). If battery voltage is present, power circuits are okay. If battery voltage is not present, check related fuse. If fuse is okay, check for an open in wire between battery and ignition switch, and between ignition switch and FICM or PCM terminal. If wiring is okay, check for a defective ignition switch.

SENSORS & SWITCHES

Note. For component locations, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS .

Note. For additional sensor testing specifications, see SENSOR OPERATING RANGE CHARTS - TRUCKS article.

Manufacturer does not provide testing procedures for many individual systems and components. For sensor and switch testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 6.0L CHEVY EXPRESS & SAVANA - BI-FUEL & CNG article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 6.0L SIERRA & SILVERADO - BI-FUEL & CNG article.

CAMSHAFT POSITION SENSOR

A malfunction in Camshaft Position (CMP) sensor can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.

CRANKSHAFT POSITION SENSOR

A malfunction in Crankshaft Position (CKP) sensor can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.

ENGINE COOLANT TEMPERATURE SENSOR

A malfunction in Engine Coolant Temperature (ECT) sensor circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article. An out-of-calibration ECT sensor may not set a DTC. Use the following procedure to test sensor calibration.

Disconnect ECT sensor harness connector. See COMPONENT LOCATIONS . Using DVOM, measure resistance of ECT sensor at specified temperatures. See SENSOR TEMPERATURE VS RESISTANCE table. Resistance should be high when engine is cold and drop as engine warms. With vehicle sitting overnight, IAT sensor and ECT sensor should have close to the same resistance reading. If resistance is not within specification, replace ECT sensor.

Temperature - °F (°C)	(1) Ohms
302 (150)	47
284 (140)	60
266 (130)	77
248 (120)	100
230 (110)	132
212 (100)	177
194 (90)	241
176 (80)	332
158 (70)	467
140 (60)	667
122 (50)	973
113 (45)	1188
104 (40)	1459
95 (35)	1802
86 (30)	2238
77 (25)	2796
68 (20)	3520
59 (15)	4450
50 (10)	5670
41 (5)	7280
32 (0)	9420
23 (-5)	12,300
14 (-10)	16,180
5 (-15)	21,450
4 (-20)	28,680
22 (-30)	52,700
40 (-40)	100,700
(1) Measure resistance across sensor terminals.

(1)	Measure resistance across sensor terminals.

SENSOR TEMPERATURE VS RESISTANCE

HEATED OXYGEN SENSORS

A malfunction in Heated Oxygen Sensor (HO2S) circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.

INTAKE AIR TEMPERATURE SENSOR

A malfunction in IAT sensor circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article. An out-of-calibration IAT sensor may not set a DTC. Use the following procedure to test sensor calibration.

Disconnect IAT sensor harness connector. See COMPONENT LOCATIONS . Using DVOM, measure resistance of IAT sensor at specified temperatures. See SENSOR TEMPERATURE VS RESISTANCE table. Resistance should be high when air temperature is cold and drop as air temperature warms. With vehicle sitting overnight, ECT sensor and IAT sensor should have close to the same resistance reading. If resistance is not within specification, replace IAT sensor.

KNOCK SENSOR

A malfunction in Knock Sensor (KS) circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.

MANIFOLD ABSOLUTE PRESSURE SENSOR

A malfunction in Manifold Absolute Pressure (MAP) sensor circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.

THROTTLE POSITION SENSOR

Note. Throttle Position (TP) sensor is not adjustable. Replace TP sensor as necessary.

A malfunction in TP sensor circuit can set a DTC. For testing procedures and specifications, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.

TRANSMISSION RANGE SWITCH

See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.

VEHICLE SPEED SENSOR

See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.

MODULES, MOTORS, RELAYS & SOLENOIDS

Note. For component locations, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS .

Note. Manufacturer does not provide testing procedures for many individual systems and components. For module, motor, relay and solenoid testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.

A/C COMPRESSOR CLUTCH RELAY

See appropriate AUTOMATIC A/C-HEATER SYSTEMS or MANUAL A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.

Scheme 75

Scheme 75: ALTERNATIVE FUEL LOCK-OFF RELAY

IDLE CONTROL SYSTEM

Note. For component locations, see COMPONENT LOCATIONS .

Note. For idle control system testing, perform related DTC testing procedure. Perform Diagnostic System Check Alternative Fuels - Engine Controls. See DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 6.0L CHEVY EXPRESS & SAVANA - BI-FUEL & CNG article or DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 6.0L SILVERADO & SIERRA - BI-FUEL & CNG article.

IGNITION SYSTEMS

Note. For ignition system testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article.

EMISSION SYSTEMS & SUB-SYSTEMS

Note. For component locations, see COMPONENT LOCATIONS .

Note. For emission and sub-system testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 6.0L CHEVY EXPRESS & SAVANA - BI-FUEL & CNG article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 6.0L SIERRA & SILVERADO - BI-FUEL & CNG article.

EXHAUST GAS RECIRCULATION

Note. For EGR system diagnosis, perform the following. On Chevy Express and Savana, see appropriate INSPECTION/MAINTENANCE PROCEDURES under DRIVE CYCLES in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L EXPRESS & SAVANA - GASOLINE article. On Sierra & Silverado, see appropriate INSPECTION/MAINTENANCE PROCEDURES under DRIVE CYCLES in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - GASOLINE article.

FUEL EVAPORATION

Note. Ensure all vacuum line and EVAP system components are not damaged or missing before proceeding with this test.

Required Service

The PCV system may require service for obstructions if any of the following conditions exist

Rough idle.
Stalling or low idle speed.
Oil leaks.
Oil in air cleaner.
Sludge in engine.

A leaking PCV valve or hose could cause

Rough idle.
Stalling.
High idle speed.

If engine idles rough, check for clogged PCV valve, or for plugged or broken PCV hoses BEFORE adjusting idle. Check PCV valve application to ensure valve is fitted. Replace PCV valve if required.

Checking PCV Valve Function

Disconnect PCV valve vacuum hose from cylinder head cover. Run engine at idle. Place thumb over open end of PCV valve vacuum hose to check for vacuum. If vacuum does not exist, check for obstruction in source vacuum supply. If source vacuum supply is okay, replace PCV valve.
Turn ignition off. Remove PCV valve. Shake valve and listen for rattle of check valve inside PCV valve. If a clear rattle is not heard, replace PCV valve.
Visually inspect valve for varnish or deposits that may make PCV valve operation sticky or restricted, or cause incomplete seating of valve. Replace as necessary.
Engine must be sealed for PCV system to function as designed. If leakage, sludging or dilution of oil is noted and PCV system is functioning properly, check engine for cause and repair as required to ensure PCV system will continue to function properly.
An engine operating without any crankcase ventilation can be damaged, so it is important to replace PCV valve and air cleaner breather (if equipped) at regular intervals (at least every 30,000 miles). Check all hoses and clamps for failure or deterioration.

MISCELLANEOUS CONTROLS

Note. For component locations, see COMPONENT LOCATIONS .

Note. Although some of the controlled devices listed here are not technically engine performance components, they can affect driveability if they malfunction.

Manufacturer does not provide testing procedures for many individual systems and components. For system and component testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 6.0L CHEVY EXPRESS & SAVANA - BI-FUEL & CNG article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 6.0L SIERRA & SILVERADO - BI-FUEL & CNG article.

A/C COMPRESSOR CLUTCH CONTROLS

Note. For A/C compressor clutch circuit testing, see appropriate AUTOMATIC A/C-HEATER SYSTEMS or MANUAL A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. See appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL for terminal and wire color identification.

TRANSMISSION

Note. For transmission electronic controls and component testing, see appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. For component circuit identification, see appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.