Engine Control System - Basic Diagnostic Procedures: Other Pontiac Vibe I

Cylinder Compression Pressure

Ensure battery is fully charged and starter motor is in good operating condition. Remove engine cover from engine. Remove 4 ignition coils from the cylinder head cover. Remove spark plugs. Remove EFI main relay from fuse/relay block 1. Install a compression gauge into a spark plug hole. Depress the clutch pedal on vehicles equipped with manual transmission. Hold throttle in Wide Open Throttle (WOT). Crank engine through 4 compression strokes for each cylinder being tested. Measure the highest pressure reading. See ENGINE COMPRESSION SPECIFICATIONS table.

ENGINE COMPRESSION SPECIFICATIONS

After testing all cylinders, install all parts removed. Compare results with the following for diagnosis

1. Normal Operation The pistons, piston rings and valves are operating normally if the cylinder compression pressure increases quickly and evenly to the compression specification.
2. Faulty Piston Rings If cylinder compression is low on the first stroke or cylinder compression increases on the following strokes but does not reach the compression specification, this indicates that the piston rings are faulty.
3. Faulty Valves If cylinder compression is low on the first stroke or cylinder compression does not increase on the following strokes, this indicates that the valves are faulty.

Exhaust System Backpressure

Before replacing any components, check exhaust system for restrictions. The exhaust system has very low back pressure under normal conditions. For dual exhaust systems a quick check of exhaust flow will help determine which side of the exhaust system is restricted. The side that has less exhaust flow is the side that will be suspect, and diagnosis should begin there. Use a vacuum gauge or a low-pressure (0-5 psi) gauge to check exhaust system.

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

1. Check At AIR Check Valve Remove AIR check valve. Install backpressure tester in place of AIR check valve.
2. Check At Oxygen Sensor Remove heated oxygen sensor in front of catalytic converter, then at post-catalyst heated oxygen sensor. Install backpressure tester in place of HO2S. Test as specified. After test is completed, coat oxygen sensor threads with anti-seize compound before installation.

Removing the AIR check valve or HO2S sensor may set a DTC. When finishing this diagnostic procedure, ensure to clear all codes.

ENGINE CRANKS BUT DOES NOT RUN

Note. For circuit reference, see WIRING DIAGRAMS . For component locations, see COMPONENT LOCATIONS in SELF-DIAGNOSTICS - 1.8L VIBE article. For connector identification, see CONNECTOR IDENTIFICATION in SELF-DIAGNOSTICS - 1.8L VIBE article.

FUEL SYSTEMS

Note. For fuel pump circuit testing, see FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 1.8L VIBE article.

FUEL SYSTEM PRESSURE RELIEF

Note. Circuit opening relay may also be called the fuel pump relay.

Fuel system is under pressure. Pressure must be relieved prior to servicing fuel system. Fuel pressure may be relieved by using one of the following methods

1. Loosen fuel filler cap to relieve the fuel tank pressure.
2. Remove the Instrument Panel (IP) storage compartment.
3. Reach in through the IP storage compartment opening and remove the circuit opening relay from the fuse block IP. (Scheme 1)
4. Start the engine and allow the engine to stall.
5. Crank the engine for an additional 3 seconds after stalling in order to assure relief of any remaining fuel pressure.
6. Disconnect and isolate the negative battery cable in order to avoid re-pressurizing fuel system. Make necessary checks or repairs. Cover the fuel system components with a shop towel before disconnecting.
7. To activate fuel system, reverse disable procedures. Check fuel system for leaks.
8. Install the IP storage compartment.
9. Install and tighten the fuel filler cap.

Scheme 1

Installing Fuel Gauge

1. Relieve the fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(ref-152426-S18326915182003020400000).
2. Remove engine cover bolts.
3. Remove engine cover.
4. Remove the quick connect coupling cover of the fuel feed hose.
5. Using the Fuel Line Disconnect Tool (J 43178), disconnect the quick connect coupling of the fuel feed hose from the fuel feed pipe of the fuel rail. (Scheme 2) Use a shop towel to catch any remaining fuel that may leak.
6. Install the Fuel Pressure Gauge Adapter (J 42982) between the fuel feed pipe of the fuel rail and of the fuel feed hose.
7. Install Fuel Pressure Gauge (J 34730-1A) to fuel pressure gauge adapter, and tighten securely. (Scheme 3)
8. Connect negative battery cable.
9. Turn ignition switch to RUN position to pressurize the fuel system. Read fuel pressure.
10. Turn ignition switch to OFF position.
11. Check for any fuel leaks.

Removing Fuel Gauge

1. Release the fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(ref-152426-S18326915182003020400000).
2. Remove the Fuel Pressure Gauge (J 34730-1A) from the Fuel Pressure Gauge Adapter (J 42982).
3. Using the Fuel Line Disconnect Tool (J 43178), disconnect the quick connect coupling of the fuel pressure gauge adapter from the fuel feed pipe of the fuel rail. (Scheme 3) Use a shop towel to catch any remaining fuel that may leak.
4. Disconnect the quick connect coupling of the fuel feed hose from the fuel pressure gauge adapter, and remove the adapter. Use a shop towel to catch any remaining fuel that may leak.
5. Connect the quick-connect fitting of the fuel feed hose to the fuel rail fuel feed pipe.
6. Install the cover for the quick connect coupling of the fuel feed hose.
7. Connect the negative battery cable. Tighten clamp bolt to specification. See «TORQUE SPECIFICATIONS»(ref-153233-S09576916932003032600000) in REMOVAL & INSTALLATION - 1.8L VIBE article.
8. Turn ignition switch to RUN position to pressurize the fuel system.
9. Turn ignition switch to OFF position.
10. Check for any fuel leaks.
11. Install engine cover.
12. Install engine cover bolts. Tighten bolts to specification. See «TORQUE SPECIFICATIONS»(ref-153233-S09576916932003032600000) in REMOVAL & INSTALLATION - 1.8L VIBE article.

Scheme 2

Scheme 3

IGNITION SYSTEMS

Note. For circuit identification, see WIRING DIAGRAMS .

Note. Some vehicles are equipped with anti-theft systems (VATS or PASS-Key(R)) which will not allow vehicle to be started if improper starting procedures or improperly coded ignition keys are used. Both fuel injection and cranking systems will be disabled. Loss of fuel enable signal from anti-theft decoder module should set a diagnostic trouble code in PCM memory.

EFI Relay

Note. The EFI relay may also be referred to as ignition relay.

See EFI RELAY under MOTORS, RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING - 1.8L VIBE article.

Crankshaft Position Sensor

If there is a fault in the CKP sensor circuits, the ignition system can malfunction. See DTC P0335: CKP SENSOR CIRCUIT under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 1.8L VIBE article.

Camshaft Position Sensor

If there is a fault in the CMP sensor circuits, the ignition system can malfunction. See DTC P0340: CMP SENSOR CIRCUIT under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 1.8L VIBE article.

IDLE SPEED & IGNITION TIMING

Ensure idle speed and ignition timing are set to specification. For specifications and adjustments, see SERVICE & ADJUSTMENT SPECIFICATIONS - VIBE and ON-VEHICLE ADJUSTMENTS - CARS articles.