Engine Controls - Remove/install/overhaul GMC Sonoma Syclone

INTRODUCTION

Removal, overhaul and installation procedures (when given by (manufacturer) are covered in this article. If component removal and installation is primarily an unbolt and bolt-on procedure, only a simple torque specification may be supplied.

ON-VEHICLE ADJUSTMENTS

Note. For adjustments, see ADJUSTMENTS article.

CONTROL UNIT

STATIC CHARGE (VOLTS)

Replacing ECM While Using 3M Anti-Static Mat. Scheme 1

Note. Before replacing ECM, carefully inspect all wiring and control components. Ignition switch must be in OFF position when connecting or disconnecting ECM connector.

Removal

Disconnect negative battery terminal. Unplug connectors from ECM. (Scheme 1) Remove ECM from vehicle. Remove PROM and CALPAC (if equipped) or MEM-CAL from ECM. See CALPAC, MEM-CAL, or PROGRAMMABLE READ-ONLY MEMORY (PROM).

Installation

Install PROM and CALPAC (if equipped) or MEM-CAL in new ECM. See CALPAC, MEM-CAL, or PROGRAMMABLE READ-ONLY MEMORY (PROM). Install ECM into vehicle. Connect electrical connectors to ECM. Install access panels. Connect negative battery terminal to battery.

Removal & Installation

Some ECM's use a CALPAC as well as a PROM. (Scheme 2) The CALPAC must also be removed from old ECM and installed in new one. Removal and replacement procedures for CALPAC are the same as for the PROM. See PROGRAMMABLE READ-ONLY MEMORY (PROM) in this article. If units are installed improperly, grounding diagnostic test lead will set Code 52.

Scheme 2

Disconnect negative battery terminal. Remove ECM from vehicle. See REMOVAL under CONTROL UNIT. Using 2 fingers, push retaining clips back from MEM-CAL. At the same time, grasp it at both ends and lift out of socket. DO NOT remove MEM-CAL cover.

1. Carefully align MEM-CAL pins with ECM pin holes. DO NOT press in middle of MEM-CAL. Push downward evenly on ends of MEM-CAL until retaining clips on ends of MEM-CAL snap into place.
2. Install ECM. Reconnect negative battery terminal. Turn ignition on and ground ALDL terminal "B". Code 12 should be flashed at least 4 times. If Code 12 is not flashed at least 4 times, other codes are present. If Code(s) 42, 43, 51 or 52 are present, or if CHECK ENGINE light stays on constantly with code(s) present, MEM-CAL is not fully seated, or is defective.

1. Remove ECM from vehicle. See REMOVAL under ELECTRONIC CONTROL MODULE (ECM) REMOVAL & INSTALLATION. Position ECM so bottom cover is facing upward. Remove slide-off PROM access cover by depressing locking tab.
2. Using PROM removal tool, grasp PROM at narrow ends. Gently rock PROM from end to end while pulling up. If installing new PROM, remove old PROM from PROM carrier.

Note. Note reference notch locations in PROM, carrier and ECM for reassembly reference.

1. Ensure new PROM has same service number as old one. Place new PROM in PROM carrier, and position squarely over ECM PROM socket. Press on PROM carrier until PROM is firmly seated in ECM. NOTE: Ensure reference notches in ECM and PROM are properly aligned. If PROM is installed backwards and ignition is turned on, PROM will be destroyed.
2. Install PROM access cover on ECM. Install ECM in vehicle. See INSTALLATION under CONTROL UNIT. Start engine, and ground ALDL terminal "B". Watch for trouble Code 51 or 52.
3. If this occurs, PROM is not fully seated in ECM, installed backwards, has bent pins, or is defective. If bent pins are cracked while straightening, replace PROM. If PROM is installed backwards or is defective, it must be replaced.

ELECTRONIC SPARK CONTROL (ESC) MODULE

Note. The ESC is located on a bracket behind the distributor, mounted to firewall.

Turn ignition off. Remove bracket-to-firewall screws. Rotate bracket to access ESC module. Disconnect ESC module harness connector. Remove ESC mounting screws and remove ESC. To install, reverse removal procedure.

FUEL SYSTEM PRESSURE RELIEF

Fuel system is under pressure. Fuel pressure may be relieved by 2 different methods.

Method 1

Disconnect fuel pump electrical connector. Start engine and allow to run until it stops. Operate starter for 3 seconds to remove remaining fuel from fuel lines.

Method 2

Install Fuel Pressure Gauge (J-34730-1) on fuel pressure connection. Wrap shop towel around pressure connection when installing fuel pressure gauge to absorb fuel leakage. Place gauge bleed hose in container. Open bleed valve to bleed fuel pressure.

THROTTLE BODY REMOVAL & INSTALLATION

Note. Identification number is stamped on throttle body near throttle shaft. Identification number must be used for ordering replacement components.

1. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF under FUEL SYSTEM (PFI) . Disconnect negative battery terminal. Loosen charge air cooler mounting bolts, and reposition charge air cooler unit to access throttle body.
2. Disconnect electrical connectors, vacuum lines, accelerator cable, throttle valve cable, and cruise control cable (if equipped). Remove throttle body screws. Remove throttle body assembly from manifold.

1. To install, reverse removal procedure using new gasket. Ensure throttle and cruise control cables do not hold throttle valve open. Tighten retaining bolts to specification. See appropriate TORQUE SPECIFICATIONS TABLE at end of article. Reset IAC valve pintle position.
2. To reset IAC valve pintle position, depress accelerator pedal slightly. Start and run engine for 5 seconds. Turn ignition off for 10 seconds. Restart engine and check for proper idle operation.

FUEL RAIL & INJECTORS

Note. Upper intake manifold must be removed in order to remove fuel rail and injectors.

1. Move air cleaner and duct aside. Drain coolant from radiator. Drain charge air cooler radiator. Relieve fuel pressure. See FUEL PRESSURE RELIEF under FUEL SYSTEM (PFI).
2. Disconnect negative battery terminal. Disconnect charge air cooler ducts and hoses. Remove charge air cooler center support bracket. Disconnect electrical connectors and hoses from EVRV solenoid, ignition coil and MAP sensor.
3. Remove multi-use bracket from lower intake manifold. Disconnect upper manifold electrical connectors and hoses. Remove throttle body from upper manifold. See THROTTLE BODY under FUEL SYSTEM (PFI).
4. Remove upper intake manifold mounting bolts. Remove upper intake manifold assembly and gasket. Disconnect heater hose at lower intake manifold. Disconnect charge air cooler inlet pipe.
5. Disconnect fuel injector electrical connectors. Disconnect fuel line at fuel rail. Remove fuel rail retaining bolts. Remove fuel rail and injectors.

To install, reverse removal procedure. Lubricate injector "O" rings with oil. Tighten fuel rail retaining bolts. See appropriate TORQUE SPECIFICATIONS TABLE at end of article.

TBI Unit Model 700

Place transmission gear selector in Park (Neutral on M/T). Set parking brake and block drive wheels. Loosen fuel filler cap to relieve tank pressure. Disconnect 3-terminal electrical connector at fuel tank. Start engine and allow to run until engine stalls. Crank engine for 3 seconds to relieve any residual pressure left in fuel lines. Fuel lines are now safe for servicing.

TBI Unit Model 220

Fuel pressure is relieved and drops to zero when ignitions is turned off.

Identification

An 8-digit unit identification number is stamped on throttle body assembly. On TBI model 220, number is stamped vertically on front of throttle body, at Throttle Position Sensor (TPS) side. On TBI model 700, number can be found on TPS side of mounting flange. Letter codes are stamped on throttle body at external tube locations to identify vacuum hose connections.

1. Disconnect air cleaner (THERMAC) hose from engine vacuum fitting (if equipped). Remove air cleaner, adapter, and gasket. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF under FUEL SYSTEM (TBI).
2. Disconnect electrical leads at IAC valve, throttle position sensor, and fuel injector(s). Disconnect fuel lines from throttle body. Discard fuel line "O" rings. Disconnect grommet with wires from throttle body. NOTE: On TBI model 220, squeeze plastic tabs on injectors and pull connector straight up.
3. Disconnect throttle linkage, return spring and cruise control linkage (if equipped). Label and disconnect all vacuum hoses from throttle body. Remove throttle body mount bolts/nut. Remove throttle body.

Note. Disassembling throttle body unit for immersion in cleaning solvent requires removal of throttle body cover or fuel meter assembly, TPS and IAC assembly. Throttle valve screws are staked in position and should NOT be removed.

Disassembly (Throttle Body Cover - Model 220)

1. Place throttle body on Holding Fixture (J-9789-118 or BT 30-15) to prevent damage to throttle valve. Remove cover-to-throttle body screws; note location of 2 short screws. Remove throttle body cover. (Scheme 3) Throttle body cover and pressure regulator are serviced as an assembly. DO NOT remove pressure regulator-to-cover screws.
2. Remove TPS, IAC, fuel injector, fuel filter, rubber parts, and diaphragms. Clean all remaining (metal) parts in a cold immersion-type cleaner such as Carbon X (X-55). Blow dry with compressed air. Inspect mating surfaces for damage which may prevent gasket sealing. Repair or replace faulty components.

Disassembly (Fuel Meter Assembly - Model 700)

1. Remove fuel meter-to-throttle body retaining screws. Remove fuel meter assembly. (Scheme 3) Discard gasket. If fuel pressure regulator cover is removed, regulator diaphragm must be replaced to prevent fuel leaks.
2. Remove TPS, IAC, pressure regulator assembly, fuel injector, fuel filter, rubber parts, and diaphragms. Clean all remaining (metal) parts in a cold immersion-type cleaner such as Carbon X (X-55). Blow dry with compressed air. Inspect mating surfaces for damage which may prevent gasket sealing. Repair or replace faulty components.

Reassembly (Throttle Body Cover - Model 220)

1. Install new dust seal into recess of throttle body. Install fuel outlet passage gasket on cover. Install throttle body cover gasket on throttle body. Install cover, making sure pressure regulator dust seal and cover gaskets are in place.
2. Apply thread locking compound to cover attaching screws. Install cover screws and lock washers. Tighten screws. Connect electrical lead to fuel injector, and install air cleaner.

Reassembly (Fuel Meter Assembly - Model 700)

1. Install new fuel meter-to-throttle body assembly gasket. Match cutout portions of gasket with openings in throttle body assembly.
2. Place fuel meter assembly on throttle body. Install fuel meter-to-throttle body retaining screws and washers (screws should be coated with locking compound). Tighten screws to specification. See TORQUE SPECIFICATIONS TABLE at end of article.
3. Install new "O" rings on fuel lines. Using a back-up wrench on fuel fittings, tighten fuel line nuts to 20 ft. lbs. (27 N.m). To complete reassembly, reverse disassembly procedure.

To install, reverse removal procedure. Ensure throttle body and intake manifold sealing surfaces are clean. Always use new throttle body gasket and fuel line "O" rings. Check fuel system for leaks by turning ignition on, but DO NOT start engine.

Scheme 3

1. Relieve fuel pressure. See FUEL PRESSURE RELIEF under FUEL SYSTEM (TBI). Remove throttle body cover, leaving cover gasket in place. Using screwdriver and fulcrum, carefully pry injector out. (Scheme 4) Remove small "O" ring from nozzle end of injector.
2. Carefully rotate injector fuel filter back and forth to remove fuel filter from base of injector. Remove and discard throttle body cover gasket. Remove large "O" ring and steel back-up washer from top counterbore of throttle body injector cavity.

1. Install fuel filter on nozzle end of fuel injector. Ensure large end of filter faces injector so filter covers raised rib at base of injector. Lubricate small "O" ring with Automatic Transmission Fluid (ATF), and push "O" ring on nozzle end of injector until it presses against injector filter.
2. Install steel back-up washer in top counterbore of throttle body injector cavity. Lubricate large "O" ring with ATF, and install "O" ring directly over back-up washer. Ensure "O" ring is seated properly in cavity, and is flush with top of throttle body casting. CAUTION: Install back-up washer and large "O" ring before installing injector. Improper seating of "O" ring will cause fuel leak.
3. Install "O" ring on injector. Install injector into cavity by aligning raised lug on injector base with cast-in notch of throttle body cavity. Push down on injector until fully seated. Electrical terminals of injector will be approximately parallel with throttle shaft. Install throttle body cover.

Relieve fuel pressure. See FUEL PRESSURE RELIEF under FUEL SYSTEM (TBI). Remove fuel injector retainer screw and retainer. Using screwdriver and fulcrum on side of injector opposite connector terminals, carefully pry injector out. (Scheme 4) Remove upper and lower "O" rings and discard.

Scheme 4

1. Lubricate new upper and lower "O" rings with engine oil and place them on injector. Ensure upper ring is in groove and lower ring is flush against filter.
2. Position injector in fuel meter assembly with electrical connector facing cutout for wire grommet.
3. Push injector down to seat in cavity. Install injector retainer. Coat injector retainer screw with thread locking compound and install. Tighten screw to 27 INCH lbs. (3.0 N.m).

Remove air cleaner and related ducting. Remove Idle Air Control (IAC) electrical connector. On model 220, unscrew IAC valve. On model 700, remove IAC retaining screws and remove IAC valve. Replace if necessary.

1. Inspect gasket or "O" ring for damage. Replace if necessary. Measure distance from IAC contact flange to tip of pintle. Distance should not exceed 1 1/8" (28 mm). If valve is extended too far, damage to valve will result during installation.
2. To set IAC pintle length on a new IAC, use finger pressure to slowly retract pintle. Lubricate new "O" ring with ATF and install new gasket. Install IAC valve on throttle body. Tighten IAC valve to specification. See TORQUE SPECIFICATIONS TABLE at end of article. CAUTION: DO NOT extend or retract pintle if IAC valve has been in service, or damage to worm gear will result.
3. Connect electrical lead to IAC valve and install air cleaner. Start engine and allow it to reach normal operating temperature. Drive vehicle at 43 MPH minimum to allow ECM to reset idle speed. It may be necessary to cycle ignition off and restart vehicle before proper idle will be initialized.

Fuel Pump

1. Relieve fuel system pressure. See FUEL SYSTEM PRESSURE RELIEF under FUEL SYSTEM (TBI). Disconnect negative battery terminal. Raise vehicle and remove fuel tank. Remove sender unit and pump by turning cam lock counterclockwise using Tool (J-36608 or J-24187).
2. Remove fuel pump from sending unit by pulling pump up into attaching hose while pulling outward from the bottom support. DO NOT damage rubber insulator or strainer. To install, reverse removal procedure.

Note. When installing sending unit, DO NOT fold or twist strainer. This will restrict fuel flow.

Information is not available from manufacturer.

Disassembly & Reassembly

1. Disassembly procedure is not available from manufacturer. (Scheme 5)-7 for exploded views of distributors.
2. When reassembling, ensure pick-up assembly arm is correctly installed on pin. If not, arm can float and cause ignition timing to vary. To prevent corrosion, lubricate terminals with petroleum jelly before installation.
3. To prevent heat damage, coat bottom of module and module rest pad in housing with silicone grease. Before installing roll pin in driven gear, ensure timing mark on roll pin and rotor tip align. (Scheme 5)-7.

Scheme 5

Scheme 6

Scheme 7

1. Remove air cleaner assembly. Disconnect electrical lead from TPS. Remove attaching screws, lock washers, retainers, and TPS.
2. To install, reverse removal procedure. Adjust TPS to specification. See «ADJUSTMENTS»(/gmc/sonoma-syclone/1991-1992/remont/adjustments/#engine-controls-adjustments) article. When replacing a TPS, ensure correct part number is used. Use Loctite on TPS attaching screws.

OXYGEN (O2) SENSOR

1. O2 sensor is mounted in the exhaust pipe, below exhaust manifold. Ensure sensor is free of contaminants. DO NOT use cleaning solvents of any type. Sensor may be difficult to remove when engine temperature is less than 120°F (48°C). Excessive removal force may damage threads in exhaust manifold or pipe.
2. Disconnect negative battery terminal. Disconnect electrical connector from O2 sensor. Carefully remove O2 sensor from exhaust pipe.

1. Whenever O2 sensor is removed, coat threads with anti-seize compound before reinstalling. New O2 sensors already have this compound applied to threads.
2. Install O2 sensor in exhaust pipe and tighten sensor to 30 ft. lbs. (41 N.m). Reconnect electrical connector to O2 sensor. Reconnect negative battery terminal.

1. Drain coolant from radiator. Remove intake air duct and turbocharger air intake duct. Remove battery, battery tray, and vacuum reservoir tank.
2. Disconnect turbocharger oil feed line and electrical connector at solenoid. Remove turbocharger coolant return line assembly.
3. Raise and support vehicle. Remove wheel assembly. Remove right-hand wheelhouse panel. Remove turbocharger outlet pipe. Remove turbocharger oil return pipe, mounting nuts and coolant feed line assembly. Remove turbocharger assembly.
4. To install, reverse removal procedure. Ensure bolts and nuts are installed in same location from which they were removed. Tighten to specification. See appropriate TORQUE SPECIFICATIONS TABLE at end of article.

1. Drain charge air cooler radiator. Remove hoses from charge air cooler. Remove charge air cooler assembly.
2. To install, reverse removal procedure. Fill charge air cooler radiator through the charge air cooler with a 56/44 mixture of coolant and distilled water. Bleed charge air cooling system. See CHARGE AIR SYSTEM BLEEDING.

1. Drain charge air cooler radiator. Remove charge air cooler radiator. See CHARGE AIR COOLER RADIATOR REMOVAL & INSTALLATION.
2. Remove charge air cooler pump mounting bolts, coolant hoses, and charge air cooler radiator bracket. Remove charge air cooler pump assembly.
3. To install, reverse removal procedure. Refill charge air system with 56/44 mixture of coolant and distilled water. Bleed charge air system. See CHARGE AIR SYSTEM BLEEDING.

1. Drain charge air cooler radiator. Raise and support vehicle. Remove air deflector shield from front of vehicle. Disconnect electrical connectors.
2. Remove clamps and hoses from charge air cooler radiator and charge air cooler pump. Remove charge air cooler radiator.
3. To install, reverse removal procedure. Fill charge air cooler radiator with a 56/44 mixture of coolant and distilled water. Bleed charge air cooling system. See CHARGE AIR SYSTEM BLEEDING.

CHARGE AIR SYSTEM BLEEDING

1. Open petcock on charge air cooler radiator. Fill charge air cooler radiator with a 56/44 mixture of coolant and distilled water. When coolant flows out of drain hole, close petcock.
2. Add coolant mixture to air charge cooler until full. Remove charge air cooler pump relay located near coil assembly. Turn ignition on. Install jumper wire between charge air cooler relay terminals "A" and "B" to operate charge air cooler pump.
3. While pump is operating, add coolant mixture to system until system is full. Install charge air cooler pressure cap.

1. Remove passenger-side wheelhouse panel. Remove retaining pin to wastegate actuator rod. Remove vacuum hose to actuator, and remove bolts securing actuator to turbocharger unit.
2. Remove wastegate actuator from turbocharger unit. To install, reverse removal procedure.

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

See also:
• ADJUSTMENTS