Preliminary Checks

Most driveability problems in the engine control system result from faulty or poor wiring, or loose and/or leaking hose connections. To avoid unnecessary component testing, a visual check should be performed before beginning trouble shooting procedures to help spot these common faults. A preliminary visual check should be made of the following areas:

Electrical connections should be checked to ensure connector terminals lock together, and wiring between each connector and wiring harness is not pinched or frayed in such a way as to produce a short to ground condition. Check the following locations to ensure that electrical connections are okay:

• Single Module Engine Controller (SMEC).
• A/C cut-out relay (if equipped).
• Starter relay.
• Cooling fan relay.
• Distributor.
• Coolant temperature sensor.
• Spark plug and coil wires.
• Throttle position sensor.
• Manifold absolute pressure sensor.
• Fuel injector harness and injectors.
• Charge temperature sensor.
• Automatic idle speed motor.
• System ground connection at left side of cylinder head.
• Engine harness to main harness.
• Alternator.
• Battery cables.
• Battery ground on engine, and engine-to-firewall ground strap.
• Canister purge solenoid and cruise control vacuum solenoid (if equipped).
• Ignition coil.
• Oxygen sensor.
• Speed sensor.
• Cooling fan motor.
• A/C condenser motor, A/C clutch, and A/C damped pressure switch (if equipped).
• Neutral safety switch.
• Transaxle lock-up solenoid.
• In-tank fuel pump.

All hose and vacuum connections should be checked to ensure connectors are fully and firmly seated. Ensure hoses and lines are not pinched, melted, or cut anywhere along the routing. Check the following locations to ensure connections and lines are okay:

• Canister purge EGR vacuum signal lines at throttle body and vacuum lines at tee in canister purge signal line.
• PCV hose at valve cover and at air intake plenum.
• EGR signal hose at EGR backpressure valve, hoses at EGR valve, hose between backpressure valve and exhaust supply tube on EGR valve, and hose between backpressure valve and EGR valve.
• Purge hose and purge signal vacuum line connector at charcoal canister, fuel tank vapor hose at canister, fuel tank vapor hose at pressure relief/roll-over valve, purge signal vacuum line connectors at purge control solenoid, and vacuum line at air intake plenum.
• Vacuum line connector at MAP sensor and at intake manifold.
• Hose at power brake booster and filter, and hose at cruise control servo (if equipped), and at air intake plenum.
• Vacuum line at power brake booster to instrument panel controls for A/C-heating control and vacuum line connector at water valve.
• Vacuum lines at canister purge solenoid and at fuel pressure regulator (leads into canister purge signal line).