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Test P - Spark Timing Check

NOTE: Perform this test when Code 18 or 49 is displayed during QUICK TEST or when directed here by other test procedures. This test is intended to diagnose the following:
  • Harness circuits (SPOUT, SAW)
  • Base timing
  • Faulty ECA
NOTE: To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault:
  • Basic engine condition (valves, vacuum leaks, valve timing, EGR valve, etc.)
  • Distributor
  • TFI, DIS or EDIS module
  • Camshaft sensor (CID)
  • Single Hall Crankshaft Sensor (PIP signal)
  • Dual Hall Sensor
Fig 1: TFI Applications Spark Timing Check Circuit
G90D13295
Fig 2: MA PFI (EDIS) IDM Circuits
G90J13291
  1. KOER Code 18: Check Computed Spark Timing  On TFI vehicles, Code 18 indicates SPOUT circuit is open. Possible causes for this fault are: open harness circuit or faulty ECA or TFI module.

    On DIS vehicles, Code 18 indicates: SPOUT circuit is open or shorted to ground. Possible causes for this fault are: an open or shorted harness or faulty ECA or DIS module.

    On EDIS vehicles, Code 18 indicates SAW circuit is either open or shorted to ground or VBAT. Possible causes for this fault are: an open or shorted harness or faulty ECA or EDIS module.

    Perform KOER SELF-TEST  and verify that Self-Test is activated. Check and record timing while in KOER SELF-TEST. Self-Test mode locks timing during testing and for a period of 2 minutes after last code is displayed. Computed timing during these 2 minutes is equal to base timing plus 20 degrees (+/-3 degrees). If timing is not to specification, go to next step.

  2. Check Base Timing  Locate in-line Spark Output (SPOUT) connector or Spark Angle Word (SAW) connector and open the connection. Start engine and check for 10 degrees BTDC base timing +/- 3 degrees. Use specification on VECI decal. If base timing is correct, reconnect SPOUT and go to next step. If base timing is incorrect, on TFI equipped vehicles adjust base timing as necessary. See ADJUSTMENTS article. After timing is reset, reconnect SPOUT and perform Computed Timing Check. On DIS and EDIS equipped vehicles, base timing is not adjustable, diagnose ignition system. See SYSTEM/COMPONENT TESTS - EEC-IV article.
  3. Check For Power to ECA  Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box. With KOEO, and DVOM set on 20-volt scale, measure voltage between test pins No. 37 and 40, and between test pins No. 57 and 60 at the breakout box. If either reading is less than 10.5 volts, go to TEST A2, step 1. If both readings are 10.5 volts or more, go to next step.
  4. Check SPOUT/SAW Circuit For Continuity  Turn key off and wait 10 seconds. Install breakout box. Disconnect ECA and TFI, EDIS or DIS (pins No. 1-6) module. With DVOM set on 200-ohm scale, measure resistance between Test Pin No. 36 at breakout box and SPOUT/SAW terminal at TFI, DIS or EDIS module vehicle harness connector. If resistance is greater than 5 ohms, repair open circuit. Reconnect all components and check timing as described in step 1. If resistance is 5 ohms or less, go to next step for DIS/EDIS equipped vehicles, or step 6 for TFI vehicles.
    Fig 3: View of Module Connectors
    G90E13296
  5. Check SPOUT/SAW Circuit For Shorts To Power (Except VREF)  Turn key off and wait 10 seconds, Install breakout box and disconnect ECA and EDIS or DIS module (pins No. 1-6). Set DVOM on 20-volt scale. Perform the following measurements:
    • Shorts to VBAT - With key off, measure voltage between Test Pin No. 36 and test pins No. 4 or 60.
    • Shorts to KEYPOWER or VPWR - With key on engine off, measure voltage between Test Pin No. 36 and test pins No. 40, or 60.

      If any voltage is less than 10.5 volts, go to next step. If any voltage is greater than 10.5 volts, service short circuit, remove breakout box, reconnect components and rerun QUICK TEST PROCEDURES .

  6. Check SPOUT/SAW Circuit For Short To VREF, GROUND, or PIP  Turn key off and wait 10 seconds. Install breakout box. Disconnect ECA and EDIS or DIS module (pins No. 1-6). Set DVOM on 200-k/ohm scale. For shorts to ground, measure resistance between Test Pin No. 36 and test pins No. 16, 20, 40, 46 and 60.

    On vehicles equipped with EDIS, a short to SIG RTN (pin No. 46) may be indicated in conjunction with an actual PWR GND short when the 4-wire HEGO sensor is connected.

    To test for shorts to VREF, measure resistance between test pins No. 36 and 26, at the breakout box.

    To test for shorts to PIP, measure resistance between test pins No. 36 and 56, at the breakout box.

    If each resistance is greater than 10 k/ohms, go to next step. If not, repair short circuit. Remove breakout box, reconnect all components and repeat QUICK TEST PROCEDURES .

  7. Check SPOUT/SAW Voltage at ECA  With key off, and breakout box installed, connect ECA to breakout box. Reconnect TFI, DIS or EDIS module. Ensure timing switch on breakout box is in DIST position. Set DVOM on 20-volt AC scale. With KOEO, measure voltage between Test Pin No. 36 and battery negative post. If voltage is not to specification, replace ECA, remove breakout box and repeat QUICK TEST PROCEDURES . If voltage is within specification, EEC-IV system is okay, remove breakout box, reconnect ECA and check ignition system. See SYSTEM/COMPONENT TESTS - EEC-IV article.
    SPOUT/SAW VOLTAGE SPECIFICATIONS

    Application Voltage
    EDIS 0.3-2.1
    All Others 4.0-10.0
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