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Test R - 2.3L EFI Fuel Control

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 25-35 psi (1.8-2.5 kg/cm2 ). If engine will not run, cycle key from off to on several times to build up fuel pressure. If fuel pressure is outside range, check electric fuel pump and fuel pressure regulator. If fuel pressure is correct, go to next step.
  2. With pressure gauge installed, cycle key from off to on several times to pressurize system. Pressure must remain at 35-45 psi (2.5-3.2 kg/cm2 ) for 60 seconds after key is turned off. If pressure is not maintained, go to step 7). If pressure is maintained, go to next step.
  3. With pressure gauge installed, cycle key from off to on several times to pressurize system. Disconnect fuel pump relay. Crank engine for 5 seconds and take pressure reading immediately after cranking. If pressure reading is 10-20 psi (0.7-1.4 kg/cm2 ) after cranking, EEC-IV system is NOT at fault for no start. If problem is rough running, missing, fuel code, or if pressure is incorrect after cranking, 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 is 200°F (93°C) pressure should drop approximately 10 psi (0.7 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 and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pins 37 and 58 for injector bank 1. Measure resistance between test pins 37 and 59 for injector bank 2. If both readings are between 7.0 and 9.5 ohms, go to step 6). If both readings are not between 7.0 and 9.5 ohms, go to next step.
  5. With key off, breakout box installed and ECA disconnected, set DVOM on 200-ohm scale. Disconnect all injectors on suspect bank. Connect each injector individually and test resistance between test pins 37 and 58 for bank 1 or between test pins 37 and 59 for bank 2. If all readings are not between 15.0 and 19.0 ohms, check harness and connectors on injector for shorted or open circuits. If circuits are okay, replace injector(s) and repeat QUICK TEST . If all readings are between 15.0 and 19.0 ohms, go to next step.
  6. With key off, breakout box installed and ECA connected, connect all injectors. Connect non-powered 12-volt test lamp between test pins 37 and 58. Crank or start engine. Repeat procedure with test lamp between test pins 37 and 59. If test lamp does not light on one or both tests, check for 12 volts at test pins 37 and 57. If test pins 37 and 57 have 12 volts, replace ECA and repeat QUICK TEST . If test lamp is bright on one or both tests, check circuits to banks 1 and 2 for short to ground. If no short is found, replace ECA and repeat QUICK TEST . If test lamp glows dimly on both tests, go to next step.
  7. Connect tachometer and run engine at idle. Disconnect and reconnect one injector at a time. Note RPM drop for each injector. If each injector does not produce at least 100 RPM drop when disconnected, replace faulty injector(s) and repeat QUICK TEST . If RPM drop is correct for all injectors, problem is in an area common to all cylinders such as vacuum leaks, fuel contamination, EGR, etc. Fuel delivery is okay.
  8. Code 42 Displayed. This code indicates an always rich condition. Turn key off and wait 10 seconds. Disconnect vehicle harness at EGO sensor. Set DVOM on 20-volt scale. Turn key on. Measure voltage between HEGO signal and ground at HEGO connector. If voltage is less than .5 volts, service short to power in HEGO circuit. If voltage reading is more than .5 volt, go to next step.
  9. Turn key off and disconnect HEGO. Set DVOM on 200,000-ohm scale. Measure resistance from key power input to HEGO circuit at the HEGO. If resistance is 10,000 ohms or less, replace HEGO and repeat QUICK TEST . If reading is 10,000 ohms or more, go to next step.
  10. Turn key off and wait 10 seconds. Disconnect vehicle harness at HEGO sensor. These non-EEC areas can cause a code 42:
    • Engine oil contaminated with fuel.
    • Misfire caused by ignition.
    • CANP malfunction.

    Disconnect vehicle harness at HEGO sensor. Ground HEGO circuit at HEGO sensor vehicle harness connector to engine block. Repeat ENGINE RUNNING SELF-TEST. If code 41 is not present, remove jumper and disconnect ECA and inspect pins for damage or corrosion. If okay, replace ECA and repeat QUICK TEST . If code 41 is present, go to next step.

  11. Turn key off, wait 10 seconds. Remove vacuum line from MAP sensor and install vacuum pump. Apply 18 in. Hg vacuum to MAP sensor. If MAP sensor does not hold vacuum, replace MAP sensor and repeat QUICK TEST . If it does hold vacuum, go to next step.
  12. Install vacuum gauge at MAP sensor and at manifold source. Start and run engine. Compare vacuum readings between MAP sensor and engine manifold. If readings are not the same, inspect vacuum lines for leaks, holes or blockage. If readings are the same, go to next step.
  13. HEGO Check. Set DVOM on 20-volt scale. With HEGO sensor disconnected from harness, connect a DVOM from HEGO sensor to engine ground. Disconnect PCV hose. Start engine and run at about 2000 RPM. If DVOM reads more than .4 volts within one minute, replace HEGO sensor and repeat QUICK TEST . If DVOM reads less than .4 volts, HEGO sensor is okay. Repeat step 1).
  14. Code 41 Verification. Run vehicle at 2000 RPM for 2 minutes. Turn key off, wait 10 seconds. Perform ENGINE RUNNING QUICK TEST . If code 41 is not present, go to step 20). If code 41 is present, go to next step.
  15. With key off, set DVOM on 20-volt scale. Remove HEGO sensor from vehicle harness. Connect DVOM to HEGO sensor and engine ground. Apply 14 in. Hg vacuum to MAP. Start engine and run at approximately 2000 RPM. If DVOM does not read greater than .5 volts within one minute, replace HEGO sensor and repeat QUICK TEST . If DVOM does read greater, go to next step.
  16. Turn key off. Install breakout box and disconnect ECA. Measure resistance between pin No.49 at breakout box and engine block ground and between HEGO circuit at HEGO vehicle harness connector and test pin No. 29 at breakout box. If both readings are more than 5 ohms, fix circuit with greater than 5 ohms resistance and repeat QUICK TEST . If both readings are less than 5 ohms, go to next step.
  17. Turn key off. Disconnect HEGO. Install breakout box and disconnect ECA. Set DVOM to 200,000-ohm scale. Measure resistance between pins No. 29 and 40 at breakout box. If resistance is 10,000 ohms or less, fix cause of resistance to ground and repeat QUICK TEST . If resistance is 10,000 ohms or greater, go to next step.
  18. Turn key off. Disconnect HEGO and set DVOM on 200,000-ohm scale. Measure resistance from ground to HEGO signal at HEGO sensor. If resistance is 10,000 ohms or less, replace HEGO and repeat QUICK TEST . If reading is 10,000 or more, go to next step.
  19. Turn key off. Reconnect HEGO sensor. Apply 14 in. Hg vacuum to MAP sensor. Start engine and run at about 2000 RPM for one minute. Allow engine to return to idle. Perform ENGINE RUNNING SELF-TEST. If code 41 is present, inspect wiring for corrosion or damage. If code 41 is not present, HEGO is okay. Go to step 1).
  20. Turn key off. Set DVOM on 200-ohm scale. Disconnect HEGO. Measure resistance between run circuit and ground at HEGO sensor. At room temperature, resistance specification is 2-5 ohms. Hot-to-warm resistance is 5 to 20 ohms. If resistance is not within specification, replace HEGO sensor. If okay, go to next step.
  21. Turn key on, engine off. Set DVOM on 20-volt scale. Connect positive lead to run circuit and negative lead to ground at HEGO vehicle harness connector. If voltage reading is 10.5 volts or greater, HEGO system is okay. Go to step 1). If reading was not 10.5 volts or greater, go to next step.
  22. Turn key off, wait 10 seconds. Set DVOM on 200-ohm scale. Measure resistance of ground circuit from HEGO vehicle harness connector to battery ground. If resistance is less than 5.0 ohms, service open in run circuit. If more than 5.0 ohms, service open ground circuit.
Fig 1: 2.3L EFI Fuel Control Circuits
G11091
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