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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 116 (Engine Controls - Self-Diagnostics - 2.2L) >> Diagnostic Tests >> DTC P0300-P0304: Cylinders No. 1-4 Misfire Detected >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ensure fuel level is more than 10 percent. Connect scan tool. Operate engine for one minute while monitoring scan tool MISFIRE CURRENT CYLS #1-4. If paired cylinders No. 1 and 4, or cylinders No. 2 and 3 misfire counters dominant or cylinders No. 1 through 4 are randomly filling up, go to next step. If a specific cylinder misfire is dominant, go to step  8 . If a specific cylinder misfire is not dominant, problem is intermittent. See DIAGNOSTIC AIDS  .
  2. If paired cylinders No. 1 and 4 or cylinders No. 2 and 3 are dominate, go to next step. If misfire is random, check the following for possible causes:
    • Large vacuum leak.
    • Fuel pressure (cycle ignition 3 times) 50-60 psi (345-414 kPa).
    • Leaking injectors (injector leakdown test) maximum 8 psi leakdown within 5 minutes.
    • Clogged fuel injectors (injector balance test) plus or minus 1.5 psi (10 kPa).
    • Fouled plugs or incorrect gap. Gap should be 0.45" (1.1 mm).
    • Sticking valves.
  3. Turn ignition off. Remove EI module from ignition coil housing and install interconnect to EI module and ensure connection is tight. Connect Noid Light (J-34730-2A) between primary ignition coil voltage pin (Pink wire) and White wire (cylinders No. 1 and 4) or Orange wire (cylinders No. 2 and 3) at EI module interconnect. Crank engine. If noid light pulses, check connector at ignition coil housing. If connector is okay, replace ignition coil housing. If noid light does not pulse, go to next step.
  4. Turn ignition off. Disconnect ECM connector J2. Turn ignition on. Touch test light between battery voltage and ECM connector J2 terminal No. 27 (White wire) for cylinders No. 1 and 4, or terminal No. 56 (Orange wire) for cylinders No. 2 and 3, for one second. If noid light pulses when circuit is connected to battery voltage, check ECM connector J1. If connector is okay, replace ECM. If noid light does not pulse when circuit is connected to battery voltage, go to next step.
  5. Disconnect EI module connector. Check continuity on White wire (cylinders No. 1 and 4) or Orange wire (cylinders No. 2 and 3) between EI module and ECM. If continuity does not exist, repair open in appropriate circuit. If continuity exists, go to next step.
  6. Check continuity between ground and ECM connector J2 terminal No. 27 (White wire) for cylinders No. 1 and 4, or terminal No. 56 (Orange Wire) for cylinders No. 2 and 3. If continuity exists, repair short to ground in White wire or Orange wire. If continuity does not exist, go to next step.
  7. Turn ignition OFF. Reconnect ECM connector J2. Turn ignition on. Measure voltage on EI module connector terminal "B" (White wire) for cylinders No. 1 and 4, or terminal "G" (Orange wire) for cylinders No. 2 and 3. If voltage is present, repair short to voltage on White wire or Orange wire. If voltage is not present, check EI module connector. If connector is okay, replace EI module.
  8. Using scan tool, monitor CALC COMPRESSION OUTPUT. If pattern is consistently stable at 00000110 or 00001001 with engine running, go to step  11 . If pattern is not stable at 00000110 or 00001001 with engine running, go to next step.
  9. Turn ignition off. Remove ignition coil housing. Check boot and spring of suspect cylinder. Replace as necessary. If boot and spring are okay, go to next step.
  10. Remove spark plug. Ensure spark plug gap is 0.045" (1.1 mm). Replace as necessary. If spark plug is okay, perform compression test. Compression should not be less than 100 psi. If compression is okay, replace spark plug. If compression is low, repair internal engine failure.
  11. Turn ignition on, engine off. Perform injector balance test. See appropriate SYSTEM & COMPONENT TESTING article. If pressure drop is within 1.5 psi (10 kPa), misfiring cylinder is flooded or spark plug is fouled. If pressure drop is not within 1.5 psi (10 kPa), go to next step.
  12. Using DVOM, measure fuel injector resistance on misfiring cylinder. If resistance is 12-13 ohms, clean fuel system and/or replace injector. Retest engine for misfire. If resistance is not 12-13 ohms, replace fuel injector.
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