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Test W

NOTE: See HOW TO USE CIRCUIT TESTS  before performing this test. Fuel contaminated engine oil may affect service codes 41 and 42. If this is suspected, remove PCV valve from valve cover and repeat QUICK TEST  . If problem is corrected, change engine oil and filter.
  1. Turn key off and wait 10 seconds. Install fuel pressure gauge. Start and run engine. Fuel pressure must be 28-38 psi (1.9-2.7 kg/cm2). If engine does not start, cycle switch from off to on several times to pressurize the system. If fuel pressure is okay, go to next step. If not, check electric fuel pump and fuel pressure regulator.
  2. Turn key off. Fuel pressure must remain within specifications for 60 seconds after key is turned off. If fuel pressure does not stay within specifications for 60 seconds, go to step 21). If fuel pressure is correct, go to next step.
  3. Turn key off. With pressure gauge installed, cycle key from off to on several times to pressurize fuel system. Locate and disconnect inertia switch. Crank engine for 5 seconds and take pressure reading immediately after cranking engine. If pressure reading drops 5-8 psi (0.4-0.6 kg/cm2 ) after cranking, EEC system is NOT at fault for no start. If problem is rough running, missing, fuel code, or if pressure does not drop, go to next step.
    NOTE: Make sure that fuel is of good quality and not contaminated by air or water as pressure readings may be incorrect with bad or contaminated fuel. Also, pressure drop will be greater when engine is cold than when engine is warm. If coolant temperature is 200°F (93°C), pressure should drop approximately 10 psi (.7 kg/cm2 ) in 5 seconds, while a pressure drop of 20 psi (1.4 kg/cm2 ) should occur in 5 seconds with engine coolant at 60°F (15.6°C).
  4. Turn key off. Set DVOM on 200-ohm range. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA disconnected. Measure resistance between test pins No. 57 and 58. If reading is less than 1.0 ohm or higher than 2.0 ohms, service harness and/or connectors on suspect injector for opens or shorts. If okay, replace injector. If reading is between 1.0 and 2.0 ohms, go to next step.
  5. With key off, breakout box installed and ECA connected, connect a non-powered, 12-volt test light between test pins No. 37 and 58. Crank or start engine. If test light does not light, check for 12 volts at test pins No. 37 and 57. If test pins No. 37 and 57 have 12 volts, replace ECA and repeat QUICK TEST  . If test light is bright, check injector circuit for shorts to ground. If no short is found, replace ECA and repeat QUICK TEST  . If test light glows dimly, fuel delivery system is okay. Problem is in area common to all cylinders such as vacuum leak, fuel contamination, EGR, etc.
  6. Start and run engine at 2000 RPM for 2 minutes. Turn key off and wait 10 seconds. Perform ENGINE RUNNING SELF-TEST. If code 41 is not present, go to step 18). If code 41 is present, go to next step.
  7. Always Lean: Code 41 Displayed. Turn key off. Set DVOM on 20-volt scale. Disconnect HEGO sensor from vehicle harness. Connect DVOM between HEGO signal at HEGO sensor and engine ground. Apply 14 in. Hg vacuum to MAP sensor. Start and run engine at 2000 RPM. If reading is less than 0.5 volts within 60 seconds, replace HEGO sensor. Repeat QUICK TEST  . If reading is greater than 0.5 volts within 60 seconds, go to next step.
  8. Turn key off. Install breakout box, leaving ECA disconnected. Disconnect HEGO sensor and set DVOM on 200-ohm scale. Measure resistance between test pin No. 49 and engine ground. Also measure resistance between HEGO circuit at HEGO harness connector and test pin No. 29. If any reading is higher than 5 ohms, repair circuit(s) having a resistance greater than 5 ohms. Repeat QUICK TEST  . If both readings are less than 5 ohms, go to next step.
  9. With key off, breakout box installed and ECA disconnected, set DVOM on 200,000-ohm scale. Disconnect HEGO sensor at harness. Measure resistance between test pins No. 29 and 40. If reading is less than 10,000 ohms, correct cause of resistance to ground and repeat QUICK TEST  . If reading is 10,000 ohms or higher, go to next step.
  10. With key off and HEGO sensor disconnected, measure resistance between power ground and HEGO signal at HEGO sensor. If reading is less than 10,000 ohms, replace HEGO sensor and repeat QUICK TEST  . If reading is 10,000 ohms or greater, go to next step.
  11. Turn key off and reconnect HEGO sensor. Apply 14 in. Hg vacuum to MAP sensor. Start and run engine at 2000 RPM for one minute. Allow engine to return to idle. Perform ENGINE RUNNING SELF-TEST. If code 41 is present, inspect ECA connector for corrosion or damaged pins. If connector is okay, replace ECA and repeat QUICK TEST  . If code 41 is not present, HEGO input circuit is okay. Go back to step 1).
  12. Always Rich: Code 42 Displayed. Turn key off and wait 10 seconds. Disconnect vehicle harness at HEGO sensor. Set DVOM on 20 volt scale. Turn key on. Measure voltage between HEGO signal and power ground at HEGO harness connector. If voltage is less than 0.5 volts, go to next step. If voltage is 0.5 volts or greater, repair short to power in HEGO circuit and repeat QUICK TEST  . If code 41 is now present, replace HEGO sensor.
  13. Turn key off and disconnect HEGO sensor. Set DVOM on 200,000-ohm scale. Measure resistance between key power input and HEGO circuit at HEGO sensor. If reading is 10,000 ohms or less, replace HEGO sensor and repeat QUICK TEST  . If reading is more than 10,000 ohms, go to next step.
  14. Turn key off and wait 10 seconds. Disconnect vehicle harness at HEGO sensor. Using jumper wire, ground HEGO circuit at HEGO sensor harness connector to engine block. Repeat ENGINE RUNNING SELF-TEST. If code 41 is present, remove jumper wire and go to next step. If code 41 is not present, disconnect ECA connector. Inspect connector for corrosion or damage. If connector is okay, replace ECA and repeat QUICK TEST  .
  15. Turn key off and wait 10 seconds. Disconnect vacuum hose from MAP sensor and connect vacuum pump to sensor. Apply 18 in. Hg vacuum to MAP sensor. If MAP sensor hold vacuum, release vacuum and go to next step. If MAP sensor does not hold vacuum, replace sensor. Connect vacuum hose and repeat QUICK TEST  .
  16. Using vacuum "T", connect vacuum gauge in intake manifold vacuum hose at MAP sensor. Start engine and note vacuum gauge. Reconnect hose to MAP sensor. Connect vacuum gauge at a different intake manifold location. Start engine and note vacuum reading. If readings differ by more than 1 in. Hg, inspect vacuum hoses for leaks, kinks, or blockage. Repair as required. If readings are within 1 in. Hg of each other, remove gauge and go to next step.
  17. Set DVOM on 20-volt scale. With HEGO sensor disconnected from harness, connect DVOM between HEGO circuit at HEGO sensor and engine ground. Disconnect PCV hose. Start and run engine at 2000 RPM. If reading is less than 0.4 volts within 30 seconds, HEGO sensor is okay. Go back to step 1). If reading is more than 0.4 volts within 30 seconds, replace HEGO sensor and repeat QUICK TEST  .
  18. Turn key on, leaving engine off. Set DVOM on 200-ohm scale. With HEGO circuit disconnected, measure resistance between run circuit and ground at HEGO sensor. With HEGO sensor hot or warm, resistance should be 5-20 ohms. If HEGO sensor is at room temperature, resistance should be 2-5 ohms. If readings are within specifications, go to next step. If not, replace HEGO sensor.
  19. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Connect positive lead to run circuit and negative lead to ground at HEGO harness connector. If reading is 10.5 volts or greater, HEGO sensor system is okay. Connect HEGO sensor and go back to step 1). If reading is less than 10.5 volts, go to next step.
  20. Turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Measure resistance of ground circuit from HEGO harness connector to battery ground. If reading is less than 5 ohms, repair open in run circuit. If reading is more than 5 ohms, repair open in ground circuit.
  21. Remove air inlet tube at fuel charging assembly. Cycle key from off to on several times to pressurize fuel system. Turn key off. Look through air horn inlet and check for fuel leaks and/or weeping at injector discharge area. If leaks are visible, replace "O" ring and/or injector. After repairs, repeat QUICK TEST  . If no leaks are visible, go to next step.
  22. Pressurize fuel system by cycling key from off to on several times. Turn key off. Look for external fuel leaks at fuel charging assembly, fuel lines, or at fittings. If leaks are found, repair fuel system as required. If no leaks are visible, replace "O" ring and/or injector. After repairs, repeat QUICK TEST  . If no leaks are visible, go to next step.
  23. Continuous Code 41 Displayed. Code 41 indicates that fuel system has not switched during closed loop fuel control. Code 41, in this situation, DOES NOT necessarily indicate a lean condition. Before attempting to correct code 41, first diagnose all other complaints such as rough idle, missing, etc. Areas to check to isolate fuel control problems are as follows:
    • Vacuum/Air Leaks. Vacuum or intake air leaks in canister purge system, PCV system, or engine sealing.
    • EGO Sensor Fuel Fouled. If fuel fouled spark plugs are observed, make complete check of ignition system. If EGO sensor is fuel fouled (low output and/or slow response), run vehicle at high (but legal) sustained speeds. Follow speed run with a few hard accelerations to burn off contamination and restore EGO sensor to correct operation.
    • Fuel Pressure. Perform step 1) and step 2).
    • Ignition System. If always in default spark (10 degrees), perform TIMING CHECK  .
    • If at this point, driveability problem is still present, perform steps 2) through 5) only.
Fig 1: Fuel Control Circuits
G6043
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