Initial Inspection and Diagnostic Overview
EARLY MODEL VEHICLESA visual inspection for loose, disconnected, damaged, or improperly routed wires and hoses should be made before attempting to diagnose the fuel injection system. A visual check will help spot these faults and save unnecessary test and diagnostic time. A thorough visual inspection includes:
1. Check battery cable connections and battery condition (clean, properly charged, etc.).
Engine Control Unit Ground:
2. Check engine control system ground connections on side of frame rail between the air cleaner and the battery.
Relay Location/Identification:
3. Check all engine control system relays for good connections and proper seating. Also check relays for physical damage and corrosion.
4. Check primary and secondary ignition leads for proper connections, routing and condition.
5. Check the air intake for restrictions (dirty air filter).
Component Loctions:
6. Check the Thermal Vacuum Switch (TVS) vacuum lines for proper routing, condition, and connections at the air cleaner.
7. Check the EGR vacuum and electrical leads for proper routing, connections, and condition.
8. Check the speed control vacuum lines for proper routing, condition and connections.
9. Check the power brake booster hose connections and condition.
10. Check the pre-heated air tube condition and connections at the air cleaner and exhaust heat stove.
11. Check the air cleaner air inlet for restrictions and check the hot air valve motor for proper operation.
12. Check the Crank Case Ventilation (CCV) hoses for proper condition and connections.
Ignition Coil-Pack:
Throttle Position Sensor And Idle Speed Regulator:
13. Check the Throttle Position Sensor (TPS) and Idle Speed Regulator (ISR) electrical leads for proper routing, connections and condition.
14. Check the ISR hoses for proper condition and connections.
Manifold Absolute Pressure Sensor And Engine Harness Connector:
15. Check the engine harness connectors for proper connections.
16. Check the Manifold Absolute Pressure (MAP) electrical and vacuum leads for proper routing, condition, and connections.
17. Check the body to engine ground strap for proper condition and connections.
EGR Valve And Transducer:
18. Check the EGR valve and transducer vacuum lines for proper routing, condition and connections. Check the EGR valve and transducer for signs of physical damage or tampering.
19. Check the engine speed sensor (Crankshaft Position Sensor -- CPS) wiring harness for proper routing, condition, and connections.
20. Check the throttle linkage, accelerator cable, cruise control cable, and throttle cable for damage, binding or sticking.
21. Check the throttle return spring for damage or fatigue.
22. Check the primary and secondary ignition leads for proper condition, routing, and connections.
23. Check the fuel injector electrical and fuel connections.
24. Check the fuel pressure regulator vacuum line for wear and/or damage.
Coolant Temperature Sensor:
25. Check the coolant temperature sensor electrical connection.
Cooling Fan Switch:
26. Check the electric cooling fan circuit for proper wire routing and connections.
27. Check the starting system circuit for proper electrical wire routing and connections.
28. Check the fuel pump electrical and fuel line connections.
LATE MODEL VEHICLES
A visual inspection for loose, disconnected, damaged, or improperly routed wires and hoses should be made prior to attempting to diagnose the fuel injection system. A visual inspection will help find these faults and save unnecessary test and diagnostic time. A thorough visual inspection includes the following:
1. Inspect battery cable connections for cleanliness and tightness. The top of the battery should be free of corrosion and dirt.
SBEC System Ground:
2. Inspect the engine control system ground connections on the side of the frame rail underneath the battery.
Power Distribution Center (PDC) And Diagnostic Connector:
Relay Location/Identification:
3. Inspect all power distribution center electrical connections. Inspect relays and distribution housing for physical damage and corrosion.
4. Inspect ignition coil electrical connections. Check secondary cables for proper routing, condition, and connections.
Ignition Coil-Pack:
5. Check the air filter for obstructions and check the vacuum lines at the air cleaner cover for proper connections and condition.
6. Check the cruise control vacuum lines for connections, routing, and condition.
7. Check the brake booster vacuum hose connections and condition.
8. Check the air pre-heater hose connections and condition.
9. Check the air cleaner hot air door for obstructions and operation. Check the vacuum hose for proper connections, routing, and condition.
Air Cleaner Vacuum Motor:
10. Check the Crankcase Ventilation (CCV) fresh air and vacuum hoses for proper connections, condition, and routing.
Throttle Position Sensor (TPS)/Automatic Idle Speed (AIS) Motor:
11. Check the Throttle Position Sensor (TPS) and Automatic Idle Speed (AIS) motor electrical connections and check the wiring for damage.
12. Check the vacuum line connections at the intake manifold for proper connections and condition.
Manifold Absolute Pressure (MAP) Sensor:
13. Check the Manifold Absolute Pressure (MAP) sensor vacuum and electrical lines for proper connections and condition.
Engine Ground:
14. Check the engine ground strap connections.
EGR Control Valve and Electronic Transducer:
15. Check the EGR valve and Electric EGR Transducer (EET) vacuum hoses and electrical connections.
Crankshaft Timing Sensor:
Camshaft Timing Sensor:
16. Check the camshaft and crankshaft sensor wiring harnesses for proper connections and condition.
17. Check the throttle linkage, accelerator cable, throttle cable, and cruise control cable for binding, sticking, or damage.
18. Check the throttle return spring, replacing it if it is weak.
19. Check the injector harness connectors for proper connections and condition. Check the wiring harness for damage.
20. Check the fuel pressure regulator vacuum line for proper connection and condition, replacing it if necessary.
Coolant Temperature Sensor (CTS):
21. Check the coolant temperature sensor electrical connector for proper connection and condition.
Charge Temperature Sensor:
22. Check the charge temperature sensor electrical connector for proper connection and condition.
23. Check the radiator fan electrical connectors for proper connection and condition.
24. Check the starter motor electrical connections for looseness or corrosion.
25. Check the oxygen sensor connector for proper connection and condition.
26. Check the alternator wiring harness for proper connections and condition. Check the alternator drive belt for proper installation and adjustment.
27. Check the canister purge hoses for proper connections and condition.
28. Check the fuel pump electrical and fuel connectors for proper connections and condition.