Engine Controls - Removal & Installation: Removal & Installation Chevrolet TrailBlazer I

Removal (4.2L)

1. Remove the air cleaner cover/resonator (2) then position the air cleaner element (6) and air outlet duct (3) out of the way. (Scheme 1)
2. Remove the air inlet duct (5) from the lower air cleaner housing/washer solvent tank assembly (4).
3. Disconnect the following electrical connectors: Windshield washer pump (1). (Scheme 5) Headlamp washer pump (2), if equipped. Low solvent level sensor (4). Lift gate washer pump (6), if equipped.
4. Remove the washer solvent level sensor wire harness from the wire harness retaining clips (3, 5).
5. If applicable, disconnect the headlamp washer hose from the headlamp washer pump located on the lower air cleaner housing/washer solvent tank. Cap the headlamp washer pump outlet fitting to prevent loss of washer solvent.
6. Disconnect the washer pump hoses (3) and plug the washer pump outlet ports to prevent loss of washer solvent. (Scheme 2)
7. Remove the 2 air cleaner housing/washer solvent tank assembly retaining nuts (1) from the mounting studs.
8. Lift the lower air filter housing/washer solvent tank assembly (2) off of the studs and remove the assembly.

Note. Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

1. Install the lower air filter housing/washer solvent tank assembly onto the mounting studs.
2. Connect the washer pump hoses (3) to the washer pumps. (Scheme 2)
3. Install the 2 air cleaner housing/washer solvent tank assembly retaining nuts (1) to the mounting studs. Tighten the nuts to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000).
4. If applicable, Connect the headlamp washer hose to the headlamp washer pump located on the lower air cleaner housing/washer solvent tank.
5. Connect the following electrical connectors: Windshield washer pump (1). (Scheme 5) Headlamp washer pump (2), if equipped. Low solvent level sensor (4). Lift gate washer pump (6), if equipped.
6. Install the washer solvent level sensor wire harness to the wire harness retaining clips (3, 5).
7. Install the air inlet duct (5) to the lower air cleaner housing/washer solvent tank assembly (4). (Scheme 1)
8. Install the air cleaner element (6) and air outlet duct (3) to the lower air cleaner housing/washer solvent tank assembly.
9. Install the air cleaner cover/resonator (2).

Scheme 1

Scheme 2

Removal (5.3L)

1. Remove the air cleaner cover (2), the filter element (6), the Mass Air Flow/Intake Air Temperature (MAF/IAT) sensor (3), and the air inlet duct (5) from the lower air cleaner housing/washer solvent tank assembly (4). (Scheme 3)
2. Disconnect the following electrical connectors: Windshield washer pump (1). (Scheme 5) Headlamp washer pump (2), if equipped. Low solvent level sensor (4). Lift gate washer pump (6), if equipped.
3. Remove the washer solvent level sensor wire harness from the wire harness retaining clips (3, 5).
4. If applicable, disconnect the headlamp washer hose from the headlamp washer pump located on the lower air cleaner housing/washer solvent tank. Cap the headlamp washer pump outlet fitting to prevent loss of washer solvent.
5. Disconnect the washer pump hoses (3) and plug the washer pump outlet ports to prevent loss of washer solvent. (Scheme 4)
6. Remove the 2 air cleaner housing/washer solvent tank assembly retaining nuts (1) from the mounting studs.
7. Lift the lower air filter housing/washer solvent tank assembly (2) off of the studs and remove the assembly.

Note. Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

1. Install the lower air filter housing/washer solvent tank assembly onto the mounting studs.
2. Connect the washer pump hoses (3) to the washer pumps. (Scheme 4)
3. Install the 2 air cleaner housing/washer solvent tank assembly retaining nuts (1) to the mounting studs. Tighten the nuts to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000).
4. If applicable, connect the headlamp washer hose to the headlamp washer pump located on the lower air cleaner housing/washer solvent tank.
5. Connect the following electrical connectors: Windshield washer pump (1). (Scheme 5) Headlamp washer pump (2), if equipped. Low solvent level sensor (4). Lift gate washer pump (6), if equipped.
6. Install the washer solvent level sensor wire harness to the wire harness retaining clips (3, 5).
7. Install the air cleaner cover (2), the filter element (6), the Mass Air Flow/Intake Air Temperature (MAF/IAT) sensor (3), and the air inlet duct (5) to the lower air cleaner housing/washer solvent tank assembly (4). (Scheme 3)

Scheme 3

Scheme 4

Scheme 5

1. Remove the air cleaner element.
2. Disconnect the electrical connector from the Intake Air Temperature (IAT) sensor (1). see scheme 6
3. Loosen the air cleaner outlet duct clamp (2) on the air cleaner side of the air cleaner outlet resonator (3).
4. Remove the air cleaner outlet duct.
5. If replacing the air cleaner outlet duct, remove the IAT sensor. See «INTAKE AIR TEMPERATURE SENSOR»(ref-159085-S18338794562003111100000) under SENSORS & SWITCHES.

Note. Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

1. If the IAT sensor was previously removed, install the IAT sensor into the air cleaner outlet duct. See «INTAKE AIR TEMPERATURE SENSOR»(ref-159085-S18338794562003111100000) under SENSORS & SWITCHES.
2. Install the air cleaner outlet duct onto the air cleaner outlet resonator (3). see scheme 6
3. Install the air cleaner element.
4. Properly position the air cleaner outlet duct clamp (2) on the air cleaner side of the air cleaner outlet resonator (3). Tighten the clamp (2) to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000).
5. Connect the electrical connector to the IAT sensor (1).

1. Loosen the clamps at the following: Mass Air Flow/Intake Air Temperature (MAF/IAT) sensor. Throttle body.
2. Remove the air cleaner outlet duct bolt. (Scheme 6)
3. Remove the air cleaner outlet duct.

Note. Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

1. Install the air cleaner outlet duct.
2. Install the air cleaner outlet duct bolt. (Scheme 6) Tighten the bolt to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000).
3. Tighten the clamps at the following: MAF/IAT sensor. Throttle body. Tighten the clamps to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000).

Scheme 6

1. Relieve the fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-159085-S07303999702003111100000). Remove throttle body assembly. See «THROTTLE BODY»(ref-159085-S22330361012003111100000). Remove Powertrain Control Module (PCM) retaining bolts and nuts. (Scheme 31) See «POWERTRAIN CONTROL MODULE»(ref-159085-S36870747962003111100000) under COMPUTERIZED ENGINE CONTROLS.
2. Remove the PCM mounting studs and position the PCM out of the way. (Scheme 31)
3. Disconnect the Engine Coolant Temperature (ECT) sensor electrical connector (1). (Scheme 7)
4. Disconnect the fuel feed (1) and fuel return (2) pipes from the fuel rail. (Scheme 8) See «FUEL LINE DISCONNECT FITTINGS (4.2L)»(ref-159085-S23542063652003111100000).
5. Disconnect the integral clip (3) from the wire harness bracket. (Scheme 8)
6. Remove the engine wire harness bracket bolt
7. Position the engine electrical wire harness bracket with wires attached out of the way. (Scheme 9)
8. Disconnect the Manifold Absolute Pressure (MAP) sensor electrical connector. (Scheme 10)
9. Disconnect the crankcase ventilation hose from the intake manifold. (Scheme 11)
10. Disconnect the vacuum brake booster hose at the intake manifold. (Scheme 12)
11. Remove the generator. See appropriate GENERATORS & REGULATORS article in ELECTRICAL. CAUTION: The intake manifold bolts are captured within the intake manifold.
12. Do not attempt to remove the bolts from the intake manifold.
13. Loosen the intake manifold bolts.
14. Remove the intake manifold. (Scheme 13)

Scheme 7

Scheme 8

Scheme 9

Scheme 10

Scheme 11

Scheme 12

Scheme 13

Install intake manifold using a NEW gasket. Tighten fasteners to specification. See TORQUE SPECIFICATIONS . To complete installation, reverse removal procedure.

Note. The intake manifold, throttle body, fuel rail, and injectors may be removed as an assembly. If not servicing the individual components, remove the manifold as a complete assembly.

1. Remove the air cleaner outlet duct. See «AIR CLEANER RESONATOR OUTLET DUCT»(ref-159085-S05754353602003111400000).
2. Relieve the fuel system pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-159085-S07303999702003111100000).
3. Disconnect the air conditioning (A/C) compressor pressure switch electrical connector (2). (Scheme 14)
4. Remove the harness clip from the cylinder head.
5. Disconnect the MAF/IAT sensor electrical connector (1). (Scheme 15)
6. Remove the harness clips from the fuel rail.
7. Disconnect the following electrical connectors: Main coil (1). (Scheme 16) Electronic throttle control (ETC) (2). Fuel injectors (3).
8. Perform the following steps in order to disconnect the fuel injector electrical connector. Mark the connectors to their corresponding injectors to ensure correct reassembly. Pull the Connector Position Assurance (CPA) retainer (2) on the connector up 1 click. (Scheme 17) Push the tab (1) on the connector in. Disconnect the fuel injector electrical connector. Repeat the steps for each injector electrical connector.
9. Disconnect the generator electrical connector. (Scheme 18)
10. Disconnect the following electrical connectors: Evaporative emission (EVAP) purge solenoid (1). (Scheme 19) Knock sensor (2). Manifold Absolute Pressure (MAP) sensor (3). Main coil (5). Fuel injectors (4).
11. Remove the electrical harness clips from the fuel rail.
12. Remove the knock sensor harness electrical connector from the intake manifold.
13. Remove the Positive Crankcase Ventilation (PCV) hose. (Scheme 20)
14. Remove the heater water shutoff valve actuator inlet hose from the intake manifold. (Scheme 21)
15. Remove the Evaporative emission (EVAP) purge solenoid vent tube by performing the following: Remove the EVAP tube end from the solenoid. (Scheme 22) Squeeze the EVAP pipe quick connect fitting retainer together. Remove the EVAP tube end from the vapor pipe.
16. Remove the vacuum brake booster hose from the rear of the intake manifold. (Scheme 23)
17. Remove the upper engine wire harness retainer nut (1). (Scheme 24)
18. Reposition the upper engine wire harness aside.
19. Remove the intake manifold bolts.
20. Remove the intake manifold. (Scheme 25)
21. Remove the intake manifold gaskets (1) from the intake manifold. (Scheme 26)
22. Discard the old intake manifold gaskets.
23. If necessary, clean and inspect the intake manifold.

1. Install NEW intake manifold gaskets (1) to the intake manifold. (Scheme 26)
2. Install the intake manifold. (Scheme 25)
3. Apply a 0.20" (5 mm) bead of Threadlock (GM P/N 12345382) to the threads of the intake manifold bolts.
4. Install the intake manifold bolts. Tighten the bolts a first pass in sequence to 44 INCH lbs (5 N.m). (Scheme 27) Tighten the bolts a final pass in sequence to 89 INCH lbs. (10 N.m).
5. Route the electrical harness into position over the engine.
6. Install the engine harness bracket nut (1). (Scheme 24) Tighten the nut to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000).
7. Install the vacuum brake booster hose to the rear of the intake manifold. (Scheme 23)
8. Install the EVAP purge solenoid vent tube. (Scheme 22)
9. Install the heater water shutoff valve actuator inlet hose to the intake manifold. (Scheme 21)
10. Install the PCV hose. (Scheme 20)
11. Install the knock sensor harness electrical connector to the intake manifold.
12. Connect the following electrical connectors: EVAP purge solenoid (1). (Scheme 19) Knock sensor (2). MAP sensor (3). Main coil (5). Fuel injectors (4).
13. Perform the following steps in order to Connect the fuel injector electrical connectors. Install the connectors to their corresponding injectors to ensure correct reassembly. Connect the fuel injector electrical connector. Push the CPA retainer (2) on the connector in 1 click. (Scheme 17) Repeat the steps for each injector electrical connector.
14. Install the harness clips to the fuel rail.
15. Connect the generator electrical connector. (Scheme 18)
16. Connect the following electrical connectors: Main coil (1). (Scheme 16) ETC (2). Fuel injectors (3).
17. Install the electrical harness clips to the fuel rail.
18. Connect the A/C compressor pressure switch electrical connector (2). (Scheme 14)
19. Install the harness clip to the cylinder head.
20. Connect the MAF/IAT sensor electrical connector (1). (Scheme 15)
21. Install the air cleaner outlet duct. See «AIR CLEANER RESONATOR OUTLET DUCT»(ref-159085-S05754353602003111400000).
22. Install the fuel fill cap.
23. Connect the negative battery cable.
24. Use the following procedure in order to inspect for leaks: Turn the ignition ON, wit the engine OFF, for 2 seconds. Turn the ignition OFF for 10 seconds. Turn the ignition ON, with the engine OFF. Inspect for fuel leaks.

Scheme 14

Scheme 15

Scheme 16

Scheme 17

Scheme 18

Scheme 19

Scheme 20

Scheme 21

Scheme 22

Scheme 23

Scheme 24

Scheme 25

Scheme 26

Scheme 27

Remove air cleaner resonator from top of engine. Disconnect EVAP canister purge line from throttle body. Disconnect throttle body harness connector. Remove 4 throttle body-to-intake manifold bolts. (Scheme 28) Remove throttle body. Remove flange gasket and discard.

Clean gasket surface on intake manifold and throttle body. Install NEW flange gasket. Install throttle body assembly. Install throttle body-to-intake manifold bolts and tighten to specification. See TORQUE SPECIFICATIONS . To complete installation, reverse removal procedure.

Scheme 28

Removal & Installation (5.3L)

Note. The intake manifold, throttle body, fuel injection rail, and fuel injectors may be removed as an assembly. If not servicing the individual components, remove the manifold as a complete assembly.

1. Remove the electrical wire harness connectors from the throttle body.
2. Remove the engine coolant air bleed hose and clamp.
3. Remove the throttle body nuts. (Scheme 29)
4. Remove the throttle body.
5. Remove the throttle body gasket. (Scheme 30)
6. Discard the gasket.
7. Remove the throttle body studs, if required. To install, reverse removal procedure.

Scheme 29

Scheme 30

Ensure ignition is off. Disconnect negative battery cable. Locate PCM at left front of engine, on intake manifold plenum. (Scheme 31) Loosen PCM harness connector bolts. Disconnect PCM harness connectors. Remove 4 PCM mounting bolts. Remove PCM from intake manifold plenum.

Scheme 31

Install PCM to intake manifold plenum. Connect harness connectors to PCM. Tighten PCM harness connector bolts to specification. See TORQUE SPECIFICATIONS . Reconnect negative battery cable. If NEW PCM has been installed, PCM MUST be programmed. See PROGRAMMING .

1. Disconnect the negative battery cable.
2. Disconnect the cooling fan electrical connector for additional clearance while removing the PCM. (Scheme 32) CAUTION: The PCM cover should be flexible enough to hold out of the way while removing the PCM. Remove the PCM cover only if replacing the cover.
3. Remove the PCM cover retainers. (Scheme 33)
4. Remove the PCM cover.
5. Release the spring latch from the PCM.
6. Release the PCM mounting tabs from the PCM. (Scheme 34)
7. Remove the PCM. CAUTION: Remove any debris from around the PCM connector surfaces before servicing the PCM. Inspect the PCM module connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminant intrusion into the PCM.
8. Loosen the PCM electrical connector bolts.
9. Disconnect the PCM electrical connectors. (Scheme 35)
10. Remove the PCM from the vehicle.

Note. Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

1. Connect the PCM electrical connectors. (Scheme 35)
2. Tighten the PCM electrical connector bolts. Tighten the bolts to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000).
3. Install the PCM. (Scheme 34)
4. Ensure that the PCM mounting tabs are engaged.
5. Secure the spring latch to the PCM.
6. Install the PCM cover and cover retainers if previously removed. (Scheme 33)
7. Connect the cooling fan electrical connector. (Scheme 32)
8. Connect the negative battery cable.
9. If the PCM was replaced the replacement PCM must be programmed. See «PROGRAMMING»(ref-159085-S24390110892003111100000).

Scheme 32

Scheme 33

Scheme 34

Scheme 35

Turn ignition off. Disconnect Accelerator Pedal Position (APP) sensor harness connector. APP sensor is located on bracket above accelerator pedal. (Scheme 36) Remove 2 APP sensor retaining screws. Remove APP sensor.

Scheme 36

Install APP sensor onto bracket above accelerator pedal. Tighten 2 APP sensor retaining screws to specification. See TORQUE SPECIFICATIONS . Reconnect harness connector to APP sensor.

1. Disconnect the accelerator pedal position (APP) sensor electrical connector. (Scheme 37)
2. Remove the 3 APP sensor bolts (1). (Scheme 38)
3. Remove the APP sensor (2).

Note. Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

1. Install the APP sensor.
2. Install the 3 APP sensor bolts (1). (Scheme 38) Tighten the bolts to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000).
3. Connect the APP sensor electrical connector. (Scheme 37)
4. Verify that the vehicle meets the following conditions: The vehicle is not in a reduced engine power mode. The ignition is ON. The engine is OFF.
5. Connect a scan tool in order to test for a proper throttle-opening and throttle-closing range.
6. Operate the accelerator pedal and monitor the throttle angles. The accelerator pedal should operate freely, without binding, between a closed throttle, and a wide open throttle.

Scheme 37

Scheme 38

Removal & Installation (4.2L)

Disconnect Camshaft Position (CMP) sensor harness connector. (Scheme 39) Remove CMP sensor retaining bolt and CMP sensor. To install, reverse removal procedure. Tighten CMP sensor retaining bolt to specification. See TORQUE SPECIFICATIONS.

Scheme 39

1. Remove the intake manifold. See «INTAKE MANIFOLD»(ref-159085-S41547677022003111200000) under AIR INDUCTION SYSTEMS. Clean area around Camshaft Position (CMP) sensor before removal to prevent debris from entering engine. CMP sensor is located at the top center rear of engine. (Scheme 40)
2. Disconnect CMP sensor harness connector. Remove CMP sensor retaining bolt. (Scheme 41) Remove CMP sensor.

Scheme 40

Scheme 41

1. Install the CMP sensor. Install the CMP sensor bolt and tighten to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000) .
2. Install the intake manifold. See «INTAKE MANIFOLD»(ref-159085-S41547677022003111200000) under AIR INDUCTION SYSTEMS.

Raise and support vehicle. Disconnect Crankshaft Position (CKP) sensor harness connector. (Scheme 42) Remove CKP sensor retaining bolt and CKP sensor.

Install CKP sensor into engine using NEW "O" ring lubricated with clean engine oil. Tighten CKP sensor retaining bolt to specification. See TORQUE SPECIFICATIONS . Reconnect CKP sensor harness connector. Lower vehicle. Perform CKP SYSTEM VARIATION LEARN PROCEDURE under PROGRAMMING.

Scheme 42

1. Disconnect negative battery cable. Raise and support vehicle. Remove right flywheel cover bolt. (Scheme 43) Remove starter mounting bolts. Disconnect oil level sensor harness connector. Slide starter forward until starter clears transmission. Disconnect electrical connectors from starter solenoid. Remove starter.
2. Clean area around Crankshaft Position (CKP) sensor before removal to prevent debris from entering engine. Disconnect CKP sensor harness connector. Remove CKP sensor retaining bolt and CKP sensor. (Scheme 44)

1. Install the CKP sensor and CKP sensor bolt. Tighten the CKP sensor bolt to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000) .
2. Connect the CKP sensor electrical connector. Install the positive cable to the starter stud. Install the starter lead nut. and Tighten the nut to specification. Install the starter solenoid lead to the solenoid stud. Install the starter solenoid nut. Tighten the starter solenoid nut to specification.
3. Slide the starter rearward. Install and tighten the starter bolts to specification. Connect the oil level sensor electrical connector. Install the right flywheel cover bolt and tighten to specification. Lower the vehicle.
4. Connect the negative battery cable. Tighten the negative battery cable bolt to specification. Perform CKP sensor variation learn procedure. See «CKP SYSTEM VARIATION LEARN PROCEDURE»(ref-159085-S15986821592003111100000) under PROGRAMMING.

Scheme 43

Scheme 44

1. Turn ignition off. Disconnect negative battery cable. Drain coolant below level of Engine Coolant Temperature (ECT) sensor into a suitable container.
2. Install a 3/8" drive breaker bar onto the drive belt tensioner. (Scheme 45) Turn breaker bar clockwise enough to relieve the tension on the drive belt. Remove drive belt. Release tension on drive belt tensioner.
3. Remove generator positive post cable nut. Remove A/C line bracket-to-engine lift hook bolt. Remove engine lift hook. Remove 3 generator mounting bolts. (Scheme 46) Remove generator.
4. Disconnect ECT sensor harness connector. (Scheme 47) ECT sensor is located on left front of engine, above thermostat housing. (Scheme 48) Remove ECT sensor.

Scheme 45

Scheme 46

Scheme 47

Scheme 48

1. Whenever ECT sensor is removed, coat threads with Sealer (12346004 or equivalent) before reinstallation. Install ECT sensor into engine and tighten to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000).
2. Reconnect harness connector to ECT sensor. Reinstall generator. Tighten generator mounting bolts to specification. Connect cable to generator positive post and tighten nut to specification. Reinstall engine lift hook. Reinstall A/C line bracket-to-engine lift hook bolt.
3. Install a 3/8" drive breaker bar onto the drive belt tensioner. (Scheme 45) Turn breaker bar clockwise enough to allow installation of drive belt. Install drive belt. Release tension on drive belt tensioner.
4. Reconnect negative battery cable. Fill and bleed cooling system. See appropriate article in ENGINES.

1. Turn OFF the ignition.
2. Raise and support the vehicle.
3. Drain the cooling system below the level of the ECT sensor.
4. Lower the vehicle.
5. Disconnect the engine coolant temperature (ECT) sensor electrical connector (1). (Scheme 49)
6. Remove the ECT sensor. (Scheme 50)

Note. Replacement components must be the correct part number for the application. Components requiring the use of the thread locking compound, lubricants, corrosion inhibitors, or sealants are identified in the service procedure. Some replacement components may come with these coatings already applied. Do not use these coatings on components unless specified. These coatings can affect the final torque, which may affect the operation of the component. Use the correct torque specification when installing components in order to avoid damage.

1. Coat the ECT sensor threads with Sealer (GM P/N 12346004). NOTE: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
2. Install the ECT sensor. (Scheme 50) Tighten the sensor to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000).
3. Connect the ECT sensor electrical connector (1). (Scheme 49)
4. Refill the engine coolant.

Scheme 49

Scheme 50

Raise and support vehicle. Disconnect fuel tank pressure sensor harness connector. (Scheme 96) Carefully remove fuel tank pressure sensor from fuel sending unit at top of fuel tank. To install, reverse removal procedure. Check for fuel leaks.

1. Raise and support the vehicle.
2. Disconnect the fuel tank pressure sensor electrical connector (3). (Scheme 51)
3. Open the retaining clip.
4. Remove the fuel tank pressure sensor. To install, reverse removal procedure.

Scheme 51

Disconnect negative battery cable. Disconnect Intake Air Temperature (IAT) sensor harness connector. IAT sensor is located in intake air duct. (Scheme 52) Pull and twist outward on IAT sensor to dislodge sensor from intake air duct.

Push and twist IAT sensor into position into the intake air duct. Reconnect harness connector to IAT sensor. Connect negative battery cable and tighten negative battery cable-to-battery bolt to specification. See TORQUE SPECIFICATIONS .

Scheme 52

Intake Air Temperature (IAT) sensor is integral with Mass Air Flow (MAF) sensor. See MASS AIR FLOW SENSOR .

Turn ignition off. Disconnect negative battery cable. Raise and support vehicle. Disconnect knock sensor harness connector(s). (Scheme 53) Remove knock sensor retaining bolt and knock sensor. To install, reverse removal procedure. Tighten knock sensor retaining bolt(s) to specification. See TORQUE SPECIFICATIONS.

Scheme 53

Note. The 5.3L has 2 knock sensors, located under intake manifold.

Remove the intake manifold. See INTAKE MANIFOLD under AIR INDUCTION SYSTEMS. Gently pry up the knock sensor rubber covers. (Scheme 54) Disconnect knock sensor harness connectors. Remove knock sensors. (Scheme 55)

Scheme 54

Scheme 55

Install the knock sensors. Tighten sensors to specification. See TORQUE SPECIFICATIONS . Push down on the rubber covers. Install the intake manifold. See INTAKE MANIFOLD UNDER AIR INDUCTION SYSTEMS.

Turn ignition off. Disconnect Manifold Absolute Pressure (MAP) sensor harness connector. (Scheme 56) MAP sensor is located on top left of engine. Press MAP sensor retainer locking tabs inward and pull upward to remove retainer from intake manifold. Remove MAP sensor from intake manifold. To install, reverse removal procedure. Replace MAP sensor seal as necessary.

Scheme 56

1. Disconnect the manifold absolute pressure (MAP) sensor electrical connector (3). (Scheme 57)
2. Remove the MAP sensor (1) from the intake manifold. (Scheme 58)

1. Install the MAP sensor (1). (Scheme 58) Push the MAP sensor down in order to engage the sensor into the retainer.
2. Connect the MAP sensor electrical connector (3). (Scheme 57)

Scheme 57

Scheme 58

1. Disconnect the MAF/IAT sensor electrical connector. (Scheme 59)
2. Loosen the clamps at the MAF/IAT sensor and the throttle body. (Scheme 60)
3. Remove the air cleaner outlet duct bolt.
4. Remove the air cleaner outlet duct.
5. Loosen the clamp attaching the MAF/IAT sensor to the air cleaner housing.
6. Remove the MAF/IAT sensor from the air cleaner housing.

1. The embossed arrow on the MAF/IAT sensor indicates the proper air flow direction. The arrow must point toward the engine. Locate the air flow direction arrow (2) on the MAF/IAT sensor connector. (Scheme 61)
2. Install the MAF/IAT sensor on to the air cleaner housing.
3. Tighten the clamp securing the MAF/IAT sensor to the air cleaner housing. (Scheme 60)
4. Install the air cleaner outlet duct.
5. Install the air cleaner outlet duct bolt. Tighten the bolt to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000).
6. Tighten the clamps at the MAF/IAT sensor and the throttle body. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000).
7. Connect the MAF/IAT electrical. (Scheme 59)

Scheme 59

Scheme 60

Scheme 61

Removal (HO2S 1)

1. Turn ignition off. Ensure oxygen sensor is free of contaminants. DO NOT use cleaning solvents of any type. Oxygen sensor may be difficult to remove when engine temperature is below 120°F (48°C). Excessive removal force may damage threads in exhaust manifold.
2. Disconnect harness connector from HO2S 1. Carefully remove HO2S 1 from exhaust manifold using Oxygen Sensor Tool (J-39194-C).

Scheme 62

Scheme 63

1. Whenever oxygen sensor is removed, coat threads with Anti-Seize Compound (5613695) before reinstallation. New oxygen sensors already have this compound applied to threads.
2. Install oxygen sensor into exhaust manifold. Tighten oxygen sensor to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000) . Reconnect harness connector to oxygen sensor.

Removal (HO2S 2)

1. Turn ignition off. Raise and support vehicle. Ensure oxygen sensor is free of contaminants. DO NOT use cleaning solvents of any type. Oxygen sensor may be difficult to remove when engine temperature is below 120°F (48°C). Excessive removal force may damage threads in exhaust pipe.
2. Disconnect harness connector from HO2S 2. Carefully remove HO2S 2 from exhaust pipe using Oxygen Sensor Tool (J-39194-B).

1. Whenever oxygen sensor is removed, coat threads with anti-seize compound (5613695) before reinstallation. New oxygen sensors already have this compound applied to threads.
2. Install oxygen sensor into exhaust pipe. Tighten oxygen sensor to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000) . Reconnect harness connector to oxygen sensor. Lower vehicle.

Removal (HO2S, Bank 1 & 2 Sensor 1)

1. Unscrew the Heated Oxygen Sensor (HO2S) sensor from the catalytic converter.
2. Remove the catalytic converter.
3. Remove the Connector Position Assurance (CPA) retainer.
4. Disconnect the HO2S electrical connector (3). (Scheme 64)and (Scheme 65).

1. Connect the HO2S electrical connector (3). (Scheme 64)
2. Install the CPA retainer.
3. Install the catalytic converter. NOTE: A special anti-seize compound is used on the HO2S threads. The compound consists of liquid graphite and glass beads. The graphite tends to burn away, but the glass beads remain, making the sensor easier to remove. New, or service replacement sensors already have the compound applied to the threads. If the sensor is removed from an exhaust component and if for any reason the sensor is to be reinstalled, the threads must have anti-seize compound applied before the reinstallation.
4. If reinstalling the old sensor, coat the threads with anti-seize compound GM P/N (12377953). NOTE: If the HO2S sensor is connected to the main wiring harness during installation. Rotate the HO2S sensor several turns counterclockwise before threading the HO2S sensor into the catalytic converter. This action of initially reverse winding of the pigtail wires will prevent a condition where the HO2S sensor pigtail wires become severely twisted or binding once the HO2S sensor is installed into the catalytic converter.
5. Install the HO2S (2). (Scheme 65) Tighten the sensor to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000).

Scheme 64

Scheme 65

Removal (HO2S, Bank 1 & 2 Sensor 2)

1. Raise and support the vehicle.
2. Remove the Connector Position Assurance (CPA) retainer. (Scheme 66)
3. Disconnect the Heated Oxygen Sensor (HO2S) electrical connector.
4. Remove the HO2S (2). (Scheme 67)and (Scheme 68).

Note. A special anti-seize compound is used on the HO2S threads. The compound consists of liquid graphite and glass beads. The graphite tends to burn away, but the glass beads remain, making the sensor easier to remove. New, or service replacement sensors already have the compound applied to the threads. If the sensor is removed from an exhaust component and if for any reason the sensor is to be reinstalled, the threads must have anti-seize compound applied before the reinstallation.

1. If reinstalling the old sensor, coat the threads with Anti-Seize Compound GM P/N (12377953).
2. Install the HO2S (2). (Scheme 67)and (Scheme 68). Tighten the sensor to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000).
3. Connect the HO2S electrical connector.
4. Install the CPA retainer. (Scheme 66)
5. Lower the vehicle.

Scheme 66

Scheme 67

Scheme 68

1. Install a 3/8" drive breaker bar onto the drive belt tensioner. (Scheme 45) Turn breaker bar clockwise enough to relieve the tension on the drive belt. Remove drive belt. Release tension on drive belt tensioner.
2. Remove 3 power steering pump mounting bolts and set power steering pump aside. Disconnect camshaft position actuator solenoid valve harness connector. Remove camshaft position actuator solenoid valve mounting bolt. (Scheme 69)
3. Remove camshaft position actuator solenoid valve. Clean any debris from camshaft position actuator solenoid valve mounting hole. To install, reverse removal procedure. Tighten fasteners to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000).

Scheme 69

1. Raise and support vehicle. Disconnect EVAP canister purge solenoid harness connector. (Scheme 70) EVAP canister purge solenoid is located on left side center of engine, below intake manifold.
2. Disconnect EVAP purge pipe and engine vacuum pipe from EVAP canister purge solenoid. Bend tab on EVAP canister purge solenoid bracket and remove EVAP canister purge solenoid from EVAP canister purge solenoid bracket. To install, reverse removal procedure.

Scheme 70

1. Push the Evaporative emission (EVAP) pipe quick connect fitting retainer inward. (Scheme 71)
2. Disconnect the EVAP pipe from the EVAP purge solenoid. (Scheme 22)
3. Disconnect the EVAP purge solenoid electrical connector (1). (Scheme 19)
4. Remove the EVAP purge solenoid bolt (2). (Scheme 72)
5. Remove the EVAP purge solenoid (3) and insulator (1).

Note. Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

1. Install the insulator (1) on the EVAP canister purge solenoid (3). (Scheme 72)
2. Install the EVAP canister purge solenoid (3).
3. Install the EVAP canister purge solenoid bolt (2). Tighten the bolt to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000).
4. Connect the EVAP purge solenoid electrical connector (1). (Scheme 19)
5. Connect the EVAP pipe to the EVAP purge solenoid. (Scheme 22)

Scheme 71

Scheme 72

1. Raise and support vehicle. Disconnect EVAP canister vent valve harness connector. EVAP canister vent valve is located near right rear corner of fuel tank. (Scheme 96)
2. Disconnect EVAP vent pipe from EVAP canister vent valve. (Scheme 73) Bend tab on EVAP canister vent valve bracket and remove EVAP canister vent valve from EVAP canister vent valve bracket. To install, reverse removal procedure.

Scheme 73

1. Raise and support the vehicle.
2. Disconnect the Evaporative emission (EVAP) canister vent valve electrical connector. see scheme 109
3. Disconnect the EVAP vent pipe from the canister vent valve.
4. Disengage the bracket retaining tab and remove the EVAP canister vent valve.

1. Install the EVAP canister vent valve onto the bracket.
2. Inspect for proper retention of the EVAP vent valve on the bracket.
3. Connect the EVAP vent pipe to the EVAP canister vent valve.
4. Connect the EVAP canister vent valve electrical connector. see scheme 109
5. Lower the vehicle.

The Throttle Actuator Control (TAC) motor is mounted to the throttle body assembly. See THROTTLE BODY .

The Idle Air Control motor is mounted permanently to the throttle body assembly and is not serviceable separately. See THROTTLE BODY .

Removal & Installation (Metal Collar)

1. Release fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-159085-S07303999702003111100000). Remove the retainer from the disconnect fitting.
2. Blow any dirt out of the disconnect fitting using compressed air. Choose correct size fitting tool from Disconnect Fitting Tool Set (J-37088-A). Insert disconnect fitting tool into female connector, then push inward to release the locking tabs. (Scheme 74) Pull connection apart.
3. Inspect all connections for dirt or burrs. If necessary, remove rust or burrs with an emery cloth. Using a clean shop towel, wipe off male tube ends. Clean or replace components and/or assemblies as necessary.
4. To install, ensure fuel line and disconnect fitting are clean. Lubricate fuel line and disconnect fitting with clean engine oil. Push both sides of disconnect fitting together to cause retaining tabs to snap into place. After connecting fitting, ensure connection is secure by pulling on both sides of disconnect fitting. Install retainer into the disconnect fitting.
5. Connect negative battery cable. Turn ignition switch to ON position for 2 seconds. Turn ignition switch to OFF position for 10 seconds. Turn ignition switch to ON position. Check for fuel leaks. Repair as necessary.

Scheme 74

Scheme 75

Removal & Installation (Plastic Collar)

1. Release fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-159085-S07303999702003111100000). Blow any dirt out of the disconnect fitting using compressed air. Squeeze the 2 plastic retainer release tabs and pull the connection apart. (Scheme 75)
2. To install, ensure fuel line and disconnect fitting are clean. Lubricate fuel line and disconnect fitting with clean engine oil. Push both sides of disconnect fitting together to cause plastic retainer release tabs to snap into place. After connecting fitting, ensure connection is secure by pulling on both sides of disconnect fitting.
3. Connect negative battery cable. Turn ignition switch to ON position for 2 seconds. Turn ignition switch to OFF position for 10 seconds. Turn ignition switch to ON position. Check for fuel leaks. Repair as necessary.

1. Release fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-159085-S07303999702003111100000). Remove the retainer from the disconnect fitting.
2. On all models except 4.3L, remove the retainers from the fuel line quick-connect fittings. Blow any dirt out of the disconnect fitting using compressed air. Choose correct size fitting tool from Disconnect Fitting Tool Set (J-37088-A). Insert disconnect fitting tool into female connector, then push inward to release the locking tabs. see scheme 82 Pull connection apart.
3. Inspect all connections for dirt or burrs. If necessary, remove rust or burrs with an emery cloth. Using a clean shop towel, wipe off male tube ends. Clean or replace components and/or assemblies as necessary.
4. To install, ensure fuel line and disconnect fitting are clean. Lubricate fuel line and disconnect fitting with clean engine oil. Push both sides of disconnect fitting together to cause retaining tabs to snap into place.
5. After connecting fitting, ensure connection is secure by pulling on both sides of disconnect fitting. Install retainer into the disconnect fitting. On all models except 4.3L, install the retainers to the fuel line quick-connect fittings.
6. Connect negative battery cable. Tighten the negative battery cable bolt. to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000). Turn ignition switch to ON position for 2 seconds. Turn ignition switch to OFF position for 10 seconds. Turn ignition switch to ON position. Check for fuel leaks. Repair as necessary.

Removal (Plastic Collar)

Note. The following instructions apply to all types of Plastic Collar Quick Connect Fittings except where indicated.

1. Relieve the fuel system pressure before servicing any fuel system connection. See «FUEL SYSTEM PRESSURE RELEASE»(ref-159085-S07303999702003111100000).
2. Using compressed air, blow any dirt out of the quick-connect fitting.
3. This step applies to Bartholomew style connectors ONLY. Squeeze the plastic quick connect fitting release tabs. (Scheme 77)
4. This step applies to Release Tab style connectors ONLY. Release the fitting by Pushing the tab toward the other side of the slot in the fitting. (Scheme 78)
5. This step applies to Squeeze to Release style connectors ONLY. Squeeze where indicated by arrows on both sides of the plastic ring surrounding the quick connect fitting. (Scheme 79)
6. This step applies to Sliding Retainer style connectors ONLY. Release the fitting by pressing on one side of the release tab causing it to push in slightly. If the tab doesn't move try pressing the tab in from the opposite side. The tab will only move in one direction. (Scheme 80)
7. Pull the connection apart. (Scheme 81)

Scheme 76

Scheme 77

Scheme 78

Scheme 79

Scheme 80

Scheme 81

1. Apply a few drops of clean engine oil to the male connection end. (Scheme 82)
2. Push both sides of the quick-connect fitting together in order to cause the retaining feature to snap into place. (Scheme 83)
3. Once installed, pull on both sides of the quick-connect fitting in order to make sure the connection is secure. (Scheme 84)

Scheme 82

Scheme 83

Scheme 84

1. Release fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-159085-S07303999702003111100000). Raise and support vehicle. Remove fuel tank shield (if equipped). (Scheme 85) Fuel filter is mounted on or near front of fuel tank.
2. Before removal, clean fuel filter connections with a spray type engine cleaner, such as GM X-30A. DO NOT use any solvent that contains Methyl Ethyl Ketone (MEK). Solvents containing MEK may damage fuel system components.
3. Disconnect fuel filter inlet and outlet disconnect fittings. See «FUEL LINE DISCONNECT FITTINGS»(ref-159085-S23542063652003111100000). Cap fuel lines to prevent contamination.
4. Remove fuel filter bracket screw. Remove fuel filter from the bracket. Drain any remaining fuel into an approved container.

Scheme 85

To install, reverse removal procedure. Tighten fuel filter bracket screw and fuel tank shield bolts to specification. See TORQUE SPECIFICATIONS . Turn ignition switch to ON position for 2 seconds. Turn ignition switch to OFF position for 10 seconds. Turn ignition switch to ON position. Check for fuel leaks. Repair as necessary.

Note. Inspect the fuel tank internally and clean the fuel tank if you find a restricted fuel filter.

1. Relieve the fuel system pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-159085-S07303999702003111100000).
2. Raise and support the vehicle.
3. Remove the fuel tank shield if equipped.
4. Clean all the fuel filter connections and the surrounding areas before disconnecting the fuel lines in order to prevent possible contamination of the fuel system.
5. Disconnect the quick connect fittings at the fuel filter. See «FUEL LINE DISCONNECT FITTINGS (5.3L)»(ref-159085-S42498279002003111900000).
6. Cap the fuel pipes in order to prevent possible fuel system contamination.
7. Remove the fuel filter bracket screw. (Scheme 86)
8. Remove the fuel filter from the bracket. (Scheme 87)

1. Install the fuel filter to the bracket. (Scheme 87)
2. Install the fuel filter bracket screw. (Scheme 86) Tighten the screws to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000).
3. Remove the caps from the fuel pipes.
4. Connect the quick connect fittings to the fuel filter. See «FUEL LINE DISCONNECT FITTINGS (5.3L)»(ref-159085-S42498279002003111900000).
5. Install the fuel tank shield if equipped.
6. Lower the vehicle.
7. Tighten the fuel fill cap.
8. Connect the negative battery cable.
9. Use the following procedure in order to inspect for leaks: Turn the ignition ON, with the engine OFF, for 2 seconds. Turn the ignition OFF for 10 seconds. Turn the ignition ON, with the engine OFF. Inspect for fuel leaks.

Scheme 86

Scheme 87

Note. Numbers in parentheses refer to numbers in illustrations.

Note. Use care in removing the fuel injectors in order to prevent damage to the fuel injector electrical connector pins or the fuel injector nozzles. Do not immerse the fuel injector in any type of cleaner. The fuel injector is an electrical component and may be damaged by this cleaning method.

Note. The engine oil may be contaminated with fuel if the fuel injectors are leaking.

1. Remove the fuel rail assembly. See «FUEL RAIL ASSEMBLY»(ref-159085-S37688524292003111400000).
2. Disconnect the fuel injector harness connector from the fuel injectors.
3. Remove the injector retainer clip. (Scheme 88)
4. Remove the fuel injector from the fuel rail.
5. Discard the injector retainer clip.
6. Remove the injector "O" ring seals from both ends of the injector. Discard the "O" ring seals.

When ordering new fuel injectors, be sure to order the correct injector for the application being serviced. The fuel injector assembly (1) is stamped with a part number identification (2). A four digit build date code (3) indicates the month (4), day (5), year (6), and the shift (7) that built the injector. (Scheme 89)

1. Lubricate the new injector "O" ring seals with clean engine oil. (Scheme 88)
2. Install the new injector "O" ring seals on the injector.
3. Install a new retainer clip on the injector.
4. Push the fuel injector into the fuel rail injector socket with the electrical connector facing outward. The retainer clip locks on to a flange on the fuel rail injector socket.
5. Install the fuel rail assembly. See «FUEL RAIL ASSEMBLY»(ref-159085-S37688524292003111400000).

Scheme 88

Scheme 89

Note. Use care in removing the fuel injectors in order to prevent damage to the fuel injector electrical connector pins or the fuel injector nozzles. Do not immerse the fuel injector in any type of cleaner. The fuel injector is an electrical component and may be damaged by this cleaning method.

1. Remove the fuel rail. See «FUEL RAIL ASSEMBLY»(ref-159085-S37688524292003111400000).
2. Remove and discard the fuel injector retainer clip (19). (Scheme 90)
3. Remove the fuel injector (17).
4. Remove and discard the fuel injector retainer clip. (Scheme 88)
5. Remove and discard the fuel injector "O" ring seals.

When ordering new fuel injectors, you must order the correct injector for the application being serviced. The fuel injector (1) is stamped with a identification part number (2). A 4-digit build date code (3) indicates the month (4), day (5), year (6), and the shift (7) that built the injector. (Scheme 89)

1. Lubricate the NEW injector "O" ring seals with clean engine oil. (Scheme 88)
2. Install the NEW injector "O" ring seals onto the injector.
3. Install a NEW retainer clip on the injector.
4. Push the fuel injector (17) into the fuel rail injector socket with the electrical connector facing outward. The retainer clip (19) locks on to a flange on the fuel rail injector socket. (Scheme 90)
5. Install the fuel rail. See «FUEL RAIL ASSEMBLY»(ref-159085-S37688524292003111400000).

Scheme 90

1. Release fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-159085-S07303999702003111100000). Remove air cleaner resonator from top of engine. Fuel pressure regulator is mounted on fuel rail near front of engine. (Scheme 91) Disconnect engine wiring harness from retaining clips at front of engine.
2. Clean area surrounding fuel pressure regulator with a spray type engine cleaner, such as GM X-30A. DO NOT use any solvent that contains Methyl Ethyl Ketone (MEK). Solvents containing MEK may damage fuel system components. Disconnect fuel pressure regulator vacuum line.
3. Place shop towel below fuel pressure regulator to catch any spilled fuel. Disconnect fuel return line at fuel pressure regulator. See «FUEL LINE DISCONNECT FITTINGS (4.2L)»(ref-159085-S23542063652003111100000).
4. Remove screws from fuel pressure regulator retainer and fuel return line retainer. Remove fuel pressure regulator retainer and fuel return line retainer. Remove fuel pressure regulator.

Scheme 91

1. Lubricate NEW "O" rings with clean engine oil. Install fuel pressure regulator into regulator housing on fuel rail. Install fuel pressure regulator retainer and fuel return line retainer. Tighten fuel pressure regulator retainer and fuel return line retainer screws to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000) .
2. Connect fuel return line at fuel pressure regulator. See «FUEL LINE DISCONNECT FITTINGS»(ref-159085-S23542063652003111100000) . Connect fuel pressure regulator vacuum line. Connect negative battery cable.
3. Turn ignition switch to ON position for 2 seconds. Turn ignition switch to OFF position for 10 seconds. Turn ignition switch to ON position. Check for fuel leaks. Repair as necessary. Install engine wiring harness into retaining clips at front of engine. Install air cleaner resonator onto top of engine.

Note. Numbers in parentheses refer to numbers in illustrations.

1. Relieve the fuel system pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-159085-S07303999702003111100000).
2. Disconnect the fuel pressure regulator vacuum line.
3. Clean any dirt from the fuel pressure regulator retainer and the surrounding area.
4. Remove the fuel pressure regulator retainer (8). (Scheme 90)
5. Remove the fuel pressure regulator (9).
6. Ensure non of the following parts are still in the fuel rail. Backup ring (10) Regulator seal "O" ring (11) Regulator filter (12) Regulator seal "O" ring (13)

1. Install the following parts onto the fuel pressure regulator (9): Backup ring (10). (Scheme 90) Regulator seal "O" ring (11) Regulator filter (12) Regulator seal "O" ring (13)
2. Lubricate the fuel pressure regulator large "O" ring (11, 13) with clean engine oil.
3. Install the fuel pressure regulator (9).
4. Install a NEW fuel pressure regulator retainer (8).
5. Connect the fuel pressure regulator vacuum line.
6. Connect the negative battery cable.
7. Install the fuel fill cap.
8. Inspect for leaks. Turn the ignition ON, for 2 seconds. Turn the ignition OFF for 10 seconds. Turn the ignition ON. Inspect for fuel leaks.

Note. DO NOT handle the fuel sending unit assembly by the fuel pipes. The amount of leverage generated by handling the fuel sending unit assembly by the fuel pipes could damage the joints.

Fuel pump is located in fuel tank and is integral with fuel sending unit assembly. Remove fuel tank. See FUEL TANK . Using compressed air, clean area at top of fuel tank around fuel sending unit. Remove fuel sending unit assembly retaining ring using Retaining Ring Remover/Installer (J-44402). Lift fuel sending unit assembly from fuel tank. Drain any remaining fuel from the fuel sending unit into an approved container. Remove and discard fuel sending unit "O" ring.

Note. Fuel pump strainer must be in a horizontal position when installing fuel tank sending unit into fuel tank. Ensure fuel pump strainer does not block the travel of the fuel sensing unit float arm.

Clean fuel sending unit sealing area. Install NEW fuel sending unit "O" ring onto the fuel tank opening. Lower fuel tank sending unit into fuel tank. Install fuel sending unit assembly retaining ring using Retaining Ring Remover/Installer (J-44402). Reinstall fuel tank. See FUEL TANK . Check for fuel leaks.

1. Relieve the fuel system pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-159085-S07303999702003111100000).
2. Remove the intake manifold. See «INTAKE MANIFOLD»(ref-159085-S41547677022003111200000).
3. Before removal, clean the fuel rail assembly and the cylinder head with a spray type engine cleaner, GM (X-30A). Follow the package instructions. Do not soak the fuel rail in liquid cleaning solvent.
4. Disconnect the fuel pressure regulator vacuum line. see scheme 99
5. Disconnect the fuel feed and return pipes (1, 2) from the fuel rail. see scheme 100 See «FUEL LINE DISCONNECT FITTINGS (4.2L)»(ref-159085-S23542063652003111100000).
6. Disconnect the fuel injector harness in-line connector.
7. Remove the fuel rail attaching bolts. see scheme 101 NOTE: Remove the fuel rail assembly carefully in order to prevent damage to the injector electrical connector terminals and the injector spray tips. Support the fuel rail after the fuel rail is removed in order to avoid damaging the fuel rail components. Cap the fittings and plug the holes when servicing the fuel system in order to prevent dirt and other contaminants from entering open pipes and passages.
8. Remove the fuel rail assembly.
9. Remove the injector lower "O" ring seal (4) from the spray tip end of each injector (3). (Scheme 88)
10. Discard the "O" ring seals.
11. If the fuel rail is not being replaced, go to the installation procedure. See «INSTALLATION»(ref-159085-S39468869762003111400000).

1. Remove the air cleaner outlet duct. See «AIR CLEANER RESONATOR OUTLET DUCT»(ref-159085-S05754353602003111400000). NOTE: An eight-digit identification number (1) is located on the fuel rail. Refer to this model identification number if servicing or part replacement is required. (Scheme 92)
2. Relieve the fuel system pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-159085-S07303999702003111100000).
3. Disconnect the air conditioning (A/C) compressor pressure switch electrical connector (2). (Scheme 93)
4. Remove the wire harness from the clip (1) on the cylinder head.
5. Disconnect the Mass Air Flow/Intake Air Temperature (MAF/IAT) sensor electrical connector (1). (Scheme 15)
6. Disconnect the generator electrical connector.
7. Disconnect the following electrical connectors on the right hand side of the engine: Coil main electrical harness (1). (Scheme 16) Electronic throttle control (ETC) (2). Fuel injectors (3).
8. Perform the following steps in order to disconnect the fuel injector electrical connectors. Mark the connectors to their corresponding injectors to ensure correct reassembly. Pull the connector position assurance (CPA) retainer (2) on the connector up 1 click. (Scheme 17) Push the tab (1) on the connector in. Disconnect the fuel injector electrical connector. Repeat the steps for each injector electrical connector.
9. Remove the electrical harness from the clips on ignition coil bracket.
10. Disconnect the following electrical connectors on the left hand side of the engine: Evaporative emission (EVAP) purge solenoid (1). (Scheme 19) Knock sensor (2). Manifold absolute pressure (MAP) sensor (3). Main coil (5). Fuel injectors (4).
11. Remove the electrical harness from the clips on ignition coil bracket.
12. Remove the positive crankcase ventilation (PCV) hose (with valve). (Scheme 20)
13. Remove the upper engine wire harness retainer nut (1). (Scheme 24)
14. Reposition the upper engine wire harness aside.
15. Disconnect the fuel feed and return pipes (1) from the fuel rail. (Scheme 94) See «FUEL LINE DISCONNECT FITTINGS (5.3L)»(ref-159085-S42498279002003111900000).
16. Disconnect the fuel pressure regulator vacuum line.
17. Remove the fuel rail bolts. (Scheme 95) NOTE: Remove the fuel rail assembly carefully in order to prevent damage to the injector electrical connector terminals and the injector spray tips. Support the fuel rail after the fuel rail is removed in order to avoid damaging the fuel rail components. Cap the fittings and plug the holes when servicing the fuel system in order to prevent dirt and other contaminants from entering open pipes and passages. CAUTION: Before removal, clean the fuel rail with a spray type engine cleaner, GM X-30A or equivalent, if necessary. Follow the package instructions. Do not soak the fuel rail in liquid cleaning solvent.
18. Remove the fuel rail.
19. Remove the fuel injector lower "O" ring seal from each injector, if necessary. (Scheme 88)
20. Discard the "O" ring seals.

1. Lubricate the NEW lower injector "O" ring seals with clean engine oil. (Scheme 88)
2. Install the NEW "O" ring seals onto each injector, if necessary.
3. Install the fuel rail. (Scheme 95)
4. Apply a 5 mm (0.020 in) band of threadlock GM P/N (12345382) to the threads of the fuel rail bolts.
5. Install the fuel rail bolts. Tighten the bolts to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000).
6. Connect the fuel pressure regulator vacuum line.
7. Connect the fuel feed and return pipes (1) to the fuel rail. (Scheme 94) See «FUEL LINE DISCONNECT FITTINGS (5.3L)»(ref-159085-S42498279002003111900000).
8. Position the upper engine wire harness over the engine.
9. Install the upper engine wire harness retainer nut (1). (Scheme 24) Tighten the nut to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000).
10. Install the PCV hose (with valve). (Scheme 20)
11. Connect the following electrical connectors on the left hand side of the engine: EVAP purge solenoid (1). (Scheme 19) Knock sensor (2). MAP sensor (3). Main coil (5). Fuel injectors (4).
12. Perform the following steps in order to Connect the fuel injector electrical connectors. Install the connectors to their corresponding injectors to ensure correct reassembly. Connect the fuel injector electrical connector. Push the CPA retainer (2) on the connector in 1 click. (Scheme 17) Repeat the steps for each injector electrical connector.
13. Install the electrical harness to the clips on ignition coil bracket.
14. Connect the following electrical connectors on the right hand side of the engine: Coil main electrical harness (1). (Scheme 16) ETC (2). Fuel injectors (3).
15. Install the electrical harness to the clips on ignition coil bracket.
16. Connect the generator electrical connector.
17. Connect the MAF/IAT sensor electrical connector (1). (Scheme 15)
18. Install the wire harness to the clip (1) on the cylinder head. (Scheme 93)
19. Connect the A/C compressor pressure switch electrical connector (2).
20. Install the air cleaner outlet duct. See «AIR CLEANER RESONATOR OUTLET DUCT»(ref-159085-S05754353602003111400000).
21. Install the fuel fill cap.
22. Connect the negative battery cable.
23. Use the following procedure in order to inspect for leaks: Turn the ignition ON, with the engine OFF, for 2 seconds. Turn the ignition OFF for 10 seconds. Turn the ignition ON, with the engine OFF. Inspect for fuel leaks.

Scheme 92

Scheme 93

Scheme 94

Scheme 95

Removal (Bravada, Envoy & Trailblazer)

1. Release fuel system pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-159085-S07303999702003111100000). Raise and support vehicle. Remove fuel tank shield (if equipped). (Scheme 85)
2. Loosen fuel fill pipe hose clamp at fuel tank. Disconnect fuel fill pipe at fuel tank. Drain as much fuel as possible from fuel tank using a hand-operated pump or equivalent. Disconnect harness connectors from fuel tank pressure sensor and EVAP vent valve. (Scheme 96)
3. Disconnect EVAP vapor pipe and EVAP vent valve pipe from EVAP canister. (Scheme 97) Disconnect fuel feed and return lines to fuel tank. See «FUEL LINE DISCONNECT FITTINGS»(ref-159085-S23542063652003111100000).
4. Cap fuel lines and EVAP pipes to prevent possible fuel system contamination. Support fuel tank. Remove fuel tank strap retaining bolts and fuel tank straps. Carefully lower fuel tank for access to fuel tank sending unit harness connector. Disconnect fuel tank sending unit harness connector. Remove fuel tank.

Position and support fuel tank. Reconnect fuel tank sending unit harness connector. Raise fuel tank and install fuel tank straps. Install fuel tank strap retaining bolts and tighten to specification. See TORQUE SPECIFICATIONS . To complete installation, reverse removal procedure.

Scheme 96

Scheme 97

Removal (Envoy XL & Trailblazer EXT)

1. Relieve the fuel system pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-159085-S07303999702003111100000).
2. Drain the fuel tank. See «FUEL TANK DRAINING»(ref-159085-S42917721922003111400000).
3. Remove the frame brace.
4. Remove the fuel tank shield, if equipped.
5. Loosen the fuel hose clamp (1) at the fuel tank. see scheme 108
6. Separate the fuel hose (2) from the fuel tank.
7. Disconnect the fuel tank pressure sensor electrical connector (3). see scheme 109
8. Disconnect the evaporative emission (EVAP) vent valve electrical connector (2).
9. Disconnect the fuel feed, return and EVAP pipes. See «FUEL LINE DISCONNECT FITTINGS (5.3L)»(ref-159085-S42498279002003111900000).
10. Cap the fuel and EVAP pipes in order to prevent possible fuel system contamination.
11. With the aid of an assistant, support the fuel tank.
12. Remove the fuel tank strap bolts (1). see scheme 110 NOTE: Do not bend the fuel tank straps. Bending the fuel tank straps may damage the straps.
13. Remove the fuel tank straps (2).
14. Carefully lower the fuel tank.
15. Disconnect the fuel sender electrical connector (1). see scheme 109
16. Remove the fuel tank.
17. Place the fuel tank in a suitable work area.
18. If the fuel tank is not being replaced, go to the installation procedure. See «INSTALLATION»(ref-159085-S16893822292003111300000).

Turn ignition off. Disconnect negative battery cable. Remove 2 air cleaner resonator mounting bolts. Loosen air cleaner resonator-to-throttle body clamp. Move air cleaner resonator aside. Disconnect harness connector(s) from ignition coil(s). Remove retaining bolt(s) from ignition coil(s). Remove ignition coil(s) from engine.

1. Install ignition coil(s) into engine. Ensure ignition coil(s) are properly seated to the valve cover. Install and tighten ignition coil retaining bolt(s) to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000) .
2. Reconnect ignition coil(s) harness connector(s). Reinstall air cleaner resonator. Tighten air cleaner resonator mounting bolts and air cleaner resonator-to-throttle body clamp to specification. Connect negative battery cable and tighten negative battery cable-to-battery bolt to specification.

1. Turn ignition off. Remove spark plug wire(s) from appropriate ignition coil(s). Twist the spark plug boot 1/2 turn. Pull only on the boot in order to remove the wire from the ignition coil.
2. Disconnect harness connector(s) from appropriate ignition coil(s). Remove retaining bolts from appropriate ignition coil(s). Remove ignition coil(s) from engine.

1. Install ignition coil. Install the ignition coil bolts. Tighten the bolts to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000) . Connect harness connector(s) to appropriate ignition coil(s).
2. Inspect the wire for proper installation. Push sideways on the boot(s) in order to inspect the seating. Reinstall any loose boot(s).

1. Turn OFF the ignition switch. NOTE: Allow the engine to cool before removing the spark plugs. Attempting to remove the spark plugs from a hot engine may cause the plug threads to seize, causing damage to cylinder head threads.
2. Remove the ignition coils. See «IGNITION COILS»(ref-159085-S05803187002003111100000).
3. Remove the spark plugs from the engine. (Scheme 98) NOTE: Clean the spark plug recess area before removing the spark plug. Failure to do so could result in engine damage because of dirt or foreign material entering the cylinder head, or by the contamination of the cylinder head threads. The contaminated threads may prevent the proper seating of the new plug. Use a thread chaser to clean the threads of any contamination.

Note. Use only the spark plugs specified for use in the vehicle. Do not install spark plugs that are either hotter or colder than those specified for the vehicle. Installing spark plugs of another type can severely damage the engine.

Note. Check the gap of all new and reconditioned spark plugs before installation. The pre-set gaps may have changed during handling. Use a round feeler gage to ensure an accurate check. Installing the spark plugs with the wrong gap can cause poor engine performance and may even damage the engine.

1. Measure the spark plug gap on the spark plugs to be installed. Compare the measurement to the gap specifications. Adjust each plug as needed. See SPARK PLUGS under IGNITION SYSTEMS in appropriate SERVICE & ADJUSTMENT SPECIFICATIONS article. NOTE: Be sure that the spark plug threads smoothly into the cylinder head and the spark plug is fully seated. Use a thread chaser, if necessary, to clean threads in the cylinder head. Cross-threading or failing to fully seat the spark plug can cause overheating of the plug, exhaust blow-by, or thread damage.
2. Install the spark plugs to the engine. (Scheme 98) Tighten the spark plugs to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000).
3. Install the ignition coils. See «IGNITION COILS»(ref-159085-S05803187002003111100000).

Scheme 98

Remove the spark plug wires. Loosen each spark plug 1 or 2 turns. Brush or air blast away any dirt from around the spark plugs. Remove the spark plugs one at a time. Place each plug in a tray marked with the corresponding cylinder numbers.

Scheme 99

1. Ensure that the correct spark plug is installed. Ensure that the spark plug has the correct heat range. Colder range spark plug causes fouling. Hotter range causes pre-ignition, causing spark plug and/or engine damage. Inspect for a bent or broken terminal post. (Scheme 99) Test for a loose terminal post by twisting and pulling the post. The terminal post should not move.
2. Inspect the insulator for flashover or carbon tracking soot. This is caused by the electrical charge traveling across the insulator between the terminal post and ground. Inspect the insulator for cracks. All or part of the electrical charge may arc through the crack instead of the electrodes.
3. Inspect for evidence of improper arcing. Measure the gap between the center electrode and the side electrode terminals. An excessively wide electrode gap can prevent correct spark plug operation. Inspect for the correct spark plug torque. Insufficient torque can prevent correct spark plug operation. An over torqued spark plug, causes the insulator to crack. Inspect for signs of tracking that occurred near the insulator tip instead of the center electrode. Inspect for a broken or worn side electrode. Inspect for a broken, worn, or loose center electrode by shaking the spark plug. A rattling sound indicates internal damage. A loose center electrode reduces the spark intensity. Inspect for bridged electrodes. Deposits on the electrodes reduce or eliminates the gap. Inspect for worn or missing platinum pads on the electrodes (if equipped). Inspect for excessive fouling. Inspect the spark plug recess area of the cylinder head for debris. Dirty or damaged threads can cause the spark plug not to seat correctly during installation.
4. A spark plug with Brown to Grayish-Tan color with small amounts of White powdery deposits are normal combustion by-products from fuels with additives. Carbon Fouled plugs with dry, fluffy Black carbon, or soot are caused by rich fuel mixtures or reduced ignition system voltage output. Excessive idling or slow speeds under light loads can keep spark plug temperatures so low that normal combustion deposits may not burn off. deposit fouling, such as oil, coolant, or additives that include substances such as silicone, (which produces very White coating), reduces the spark intensity. Most powdery deposits will not effect spark intensity unless they form into a glazing over the electrode.

Properly position each spark plug washer. Inspect each spark plug gap. Adjust each plug as needed. See SPARK PLUGS under IGNITION SYSTEMS in appropriate SERVICE & ADJUSTMENT SPECIFICATIONS article. Hand start the spark plugs in the corresponding cylinders. Tighten the spark plugs to specification. See TORQUE SPECIFICATIONS .

1. Remove the spark plug wire from the spark plug. (Scheme 100) Twist each spark plug 1/2 turn. Pull only on the boot in order to remove the wire from each spark plug.
2. Remove the spark plug wire from the ignition coil. Twist each spark plug boot 1/2 turn. Pull only on the boot in order to remove the wires from the ignition coil.

1. Install the spark plug wire to the ignition coil. (Scheme 100)
2. Install the spark plug wire to the spark plug.
3. Inspect the wires for proper installation: Push sideways on each boot in order to inspect the seating. Reinstall any loose boot.

Scheme 100

1. Raise and support vehicle. Remove fuel tank shield (if equipped). (Scheme 85) Disconnect EVAP vapor pipe and EVAP vent valve pipe from EVAP canister. (Scheme 97)
2. Disconnect EVAP purge pipe from EVAP canister. (Scheme 101) Move rear of EVAP canister forward in the EVAP canister bracket to release EVAP canister bracket rear tabs. (Scheme 102) Remove EVAP canister from EVAP canister bracket front tab and remove EVAP canister.

1. Install EVAP canister into EVAP canister bracket front tab and press rear of EVAP canister into the EVAP canister bracket rear tabs. (Scheme 102)
2. Reconnect EVAP vapor pipe and EVAP vent valve pipe to EVAP canister. (Scheme 97) Reconnect EVAP purge pipe to EVAP canister. (Scheme 101)
3. Reinstall fuel tank shield (if equipped). (Scheme 85) Tighten fuel tank shield bolts to specification. See «TORQUE SPECIFICATIONS»(ref-159085-S35886898402003111100000). Lower vehicle.

Scheme 101

Scheme 102

Removal (Envoy XL & TrailBlazer EXT

1. Raise the vehicle.
2. Remove the fuel tank. See «FUEL TANK»(ref-159085-S41505104902003111100000).
3. Disconnect the evaporative emission (EVAP) vapor pipe (2) from the EVAP canister. (Scheme 103)
4. Disconnect the EVAP vent pipe (1) from the EVAP canister.
5. Disconnect the EVAP purge pipe from the EVAP canister. The purge pipe is the small pipe next to the vapor pipe (2). CAUTION: Do not pry against the surface of the evaporative emissions canister. This could damage the canister.
6. Remove the EVAP canister from the tabs of the canister bracket by inserting a flat head screwdriver into the center slots of the tabs as indicated in the illustration. (Scheme 104)
7. Pry the canister away from the tabs as indicated in the illustration.
8. Slide the canister away from the single tab side to disengage the EVAP canister from the bracket.

1. Slide the EVAP canister into the single tab side and press the canister into the two tab side. Ensure the tabs have completely engaged.
2. Connect the EVAP purge pipe to the EVAP canister. The purge pipe is the small pipe next to the vapor pipe (2). (Scheme 103)
3. Connect the EVAP vent pipe (1) to the EVAP canister.
4. Connect the EVAP vapor pipe (2) to the EVAP canister.
5. Install the fuel tank. See «FUEL TANK»(ref-159085-S41505104902003111100000).
6. Lower the vehicle.

Scheme 103

Scheme 104

See EVAP CANISTER PURGE SOLENOID under MOTORS, RELAYS & SOLENOIDS.

See EVAP CANISTER VENT VALVE under MOTORS, RELAYS & SOLENOIDS.