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Home >> Ford >> 1990 >> Escort GT >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 1.9L >> PFI Service Code Definitions >> Test KE - Idle Speed Control (Air By-Pass)

Test KE - Idle Speed Control (Air By-Pass)

NOTE: Perform this test when Code 12, 13, 16, 17, 19, 47 or 48 is displayed during QUICK TESTS or when directed here by other test procedures. If engine is running rough or has rough idle, correct these conditions before performing test. Causes may be in ignition system, fuel system or EGR system. This test is intended to diagnose only the following:
  • RPM during Self-Test mode
  • ISC solenoid
  • Harness circuits (ISC and VPWR)
  • Faulty ECA
NOTE: To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault:
  • Engine temperature not up to operating temperature
  • Engine over operating temperature
  • A/C input (electrical problem)
  • Incorrect idle speed or throttle stop adjustment
  • Faulty cruise control linkage
Fig 1: Idle Speed Control (Air By-Pass) Circuit
G90G13140
  1. 1) Code 12: Check For RPM Drop  On 1.9 PFI engine, Code 12 indicates that during KOER SELF-TEST, engine was unable to reach maximum self-test RPM.

    On all other models, Code 12 indicates that during KOER SELF-TEST engine RPM could not be controlled within self-test upper RPM limit.

    Possible causes for this fault are:

    • Open or shorted circuit
    • Sticking or binding throttle linkage
    • Incorrect idle adjustment
    • Throttle body or ISC solenoid contaminated
    • Faulty ISC solenoid
    • Faulty ECA
    • Non-ECC mechanical faults that could affect RPM

      Turn key off. Connect engine tachometer and start engine. Disconnect Idle Speed Control (ISC) harness. If RPM drops or if engine stalls, go to next step. If not, go to step 3.

  2. 2) Check For EGR Codes  If EGR service codes 31, 32, 33 or 34 are displayed, reconnect ISC solenoid and go to KOER CODE CHART and perform appropriate test under CIRCUIT TESTS . If these codes are not displayed, go to next step.
  3. 3) Check For Other EEC-IV Codes  If Codes 22, 41, 42, 91, or 92 are displayed, reconnect ISC solenoid, go to KOER CODE CHART and perform appropriate CIRCUIT TESTS  (except PFI, go to next step). If these codes are not displayed, go to next step.
  4. 4) Measure ISC Solenoid Resistance  Turn key off. Disconnect ISC solenoid. Set DVOM on 200-ohm scale, and measure resistance of ISC solenoid. Connect DVOM positive (+) lead to VPWR terminal and DVOM negative lead to ISC terminal as ISC solenoid is equipped with a diode. If resistance is between 7 and 13 ohms, go to next step. If resistance is less than 7 ohms or greater than 13 ohms, replace ISC solenoid and repeat QUICK TEST PROCEDURES .
    Fig 2: ISC Solenoid Connector
    G90H13141
  5. 5) Check For Internal Short to ISC Solenoid Case  With key off and ISC solenoid disconnected, set DVOM on 200-k/ohm scale. Measure resistance from either ISC terminal pin to ISC solenoid housing. If reading is greater than 10 k/ohms, go to next step. If reading is 10 k/ohms or less, replace ISC solenoid. Repeat QUICK TEST PROCEDURES .
  6. 6) Check VPWR Circuit Voltage  Leave ISC harness disconnected. With KOEO, set DVOM on 20-volt scale. Measure voltage between VPWR circuit at ISC harness connector and battery ground terminal. If reading is less than 10.5 volts, repair open in circuit and repeat QUICK TEST PROCEDURES . If reading is 10.5 volts or more, go to next step.
  7. 7) Check ISC Circuit Continuity  Turn key off and wait 10 seconds. Leave ISC solenoid disconnected. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA disconnected. With DVOM on 200-ohm scale, measure resistance between test pin No. 21 and ISC circuit at ISC vehicle harness connector. If reading is greater than 5 ohms, repair open circuit, remove breakout box and reconnect all components. Repeat QUICK TEST PROCEDURES . If reading is less than 5 ohms, go to next step.
  8. 8) Check ISC Circuit For Short to Ground  Turn key off and wait 10 seconds. Leave ISC solenoid disconnected. Install breakout box, leaving ECA disconnected. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 21 and test pins No. 40, 46, and 60. If any reading is less than 10 k/ohms, repair short to ground and repeat QUICK TEST PROCEDURES . If all readings are 10 k/ohms or more, go to next step.
  9. 9) Check ISC Circuit For Short to Power  Turn key off and wait 10 seconds. Leave breakout box installed. Leave ECA and ISC solenoid disconnected. Set DVOM on 200-k/ohm scale. Measure resistance by connecting DVOM negative lead to test pin No. 21 and positive lead to test pin No. 37. If reading is greater than 10 k/ohms, go to next step. If reading is 10 k/ohms or less, repair short circuit and remove breakout box. Reconnect all components and repeat QUICK TEST PROCEDURES . If code or symptom is still present, replace ECA.
  10. 10) Check ISC Signal From ECA  With key off, reconnect ECA and ISC. Leave breakout box installed and set DVOM on 20-volt scale. Connect DVOM between test pins No. 21 and 40. Start engine and observe DVOM while slowly increasing and decreasing engine RPM. If DVOM voltage reading varies, go to next step. If DVOM voltage reading does not vary, replace ECA and repeat QUICK TEST PROCEDURES .
  11. 11) Check Base Idle  Verify base idle speed, see ADJUSTMENTS article. If base idle speed is within specifications, remove ISC solenoid and inspect for contamination, service as necessary. Rerun QUICK TEST PROCEDURES . If code or symptom is still present, replace ISC solenoid. If curb idle speed is incorrect, reset idle speed to specification. Rerun QUICK TEST. If unable to set idle to specification, go to next step.
  12. 12) 12) Check Faults Which Affect Idle Speed  Check the following mechanical items for faults:
    • Throttle linkage and/or cruise control linkage for sticking or binding
    • Throttle body for contamination
    • Vacuum hoses (check emission decal)
    • Check for leaks around ISC solenoid (gaskets, etc.)

    If all of the above items are okay, remove ISC solenoid and inspect for contamination. Service as necessary and rerun QUICK TEST PROCEDURES . If code or symptom is still present, replace ISC. If any of the above items are faulty, service as needed. Remove breakout box. Reconnect components. Rerun QUICK TEST.

    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 12 to step 15. No test procedures have been omitted.
  13. 15) Code 13: Verify Idle Speed is Within Specification  On PFI engines, Code 13 indicates that during KOER SELF-TEST, engine RPM did not reach lower limit. On all other engines, Code 13 indicates engine could not be controlled within lower RPM range during self-test. Possible causes for this fault are:
    • Incorrect idle setting
    • Vacuum leaks
    • Sticking or binding throttle linkage
    • Throttle plates open
    • Incorrect ignition timing (TFI ignition only)
    • Throttle body or ISC solenoid contamination
    • ISC circuit shorted to ground
    • Faulty ISC solenoid

    If all of the above components are okay and idle is set to specification, remove ISC solenoid and inspect for contamination. Service as necessary and rerun QUICK TEST PROCEDURES . If code or symptom is still present, replace ISC solenoid. If idle speed is not set to specification, reset and rerun QUICK TEST. If idle speed cannot be reset to specification, go to next step.

  14. 16) Check For Conditions Affecting Idle Speed  Check the following mechanical components for faults:
    • Engine vacuum hoses (refer to emission decal)
    • Throttle linkage and/or cruise control linkage for sticking or binding
    • Ensure throttle plates are fully closed
    • Check for vacuum leaks in induction system
    • Check throttle body for contamination
    • Ensure base ignition timing is to specification on emission decal (TFI vehicles only)

    If all above checks are okay, go to next step. If a fault has been found, service as necessary and rerun QUICK TEST PROCEDURES .

  15. 17) Check For Internal Short to ISC Solenoid Case  With key off and ISC solenoid disconnected, set DVOM on 200-k/ohm scale. Measure resistance from either ISC terminal pin to ISC solenoid housing. If reading is greater than 10 k/ohms, go to next step. If reading is 10 k/ohms or less, replace ISC solenoid. Repeat QUICK TEST PROCEDURES .
  16. 18) Check ISC Circuit For Short to Ground  Turn key off and wait 10 seconds. Leave ISC solenoid disconnected. Disconnect ECA 60-pin connector. Inspect for damaged or corroded terminal pins. Service as necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 21 and test pins No. 40, 46, and 60. If any reading is less than 10 k/ohms, repair short to ground and remove breakout box. Reconnect components and repeat QUICK TEST PROCEDURES . If all readings are 10 k/ohms or more, go to next step.
  17. 19) Check ISC Signal From ECA  With key off, connect ECA and ISC. Leave breakout box installed and set DVOM on 20-volt scale. Connect DVOM between test pins No. 21 and 40. Start engine and observe DVOM while slowly increasing and decreasing engine RPM. If DVOM voltage reading varies, remove ISC solenoid and inspect for contamination, service as necessary. Rerun QUICK TEST PROCEDURES . If code or symptom is still present, replace ISC solenoid. If DVOM voltage does not vary, replace ECA and rerun QUICK TEST.
  18. 20) Code 47: Check For Low Flow of Unmetered Air  Code 47 indicates that measured airflow at base idle was lower than ECA specification. Possible causes for this fault are: air/vacuum leaks in fuel charging system or faulty or leaking purge solenoid and/or leaking injector "O" rings. Check for holes, cracks and or disconnections in fuel charging assembly. Check for a stuck open purge solenoid or injector "O" rings. Service any faults as necessary and rerun QUICK TEST PROCEDURES . If no faults are present, EEC-IV system is okay. Service other codes as necessary.
  19. 21) Code 48: Check For High Flow of Unmetered Air  Code 48 indicates that measured airflow at base idle was higher than ECA specification. Possible causes for this fault are: air/vacuum leaks in fuel charging system or loss of ignition or fuel.

    Check for and repair holes, cracks, and/or bad connections at air cleaner outlet tube (between vane airflow meter and fuel charging assembly). Check for loss of ignition or injection on one or more cylinders. If any faults are found, service as necessary. Rerun QUICK TEST PROCEDURES . If no faults are found, EEC-IV system control of metered airflow is okay. Service other codes as necessary.

  20. 22) Code 16: High ISC RPM  Code 16 indicates that with ISC off, engine RPM was greater than self-test specification limit. Possible causes for this fault are:
    • Incorrect idle adjustment
    • Faulty purge solenoid
    • Air or vacuum leaks

    If Code 48 is also present, reset throttle plate. Refer to Vehicle Emission Control Decal for curb idle set procedure. Rerun QUICK TEST PROCEDURES . If Code 48 is still present, go back to step 21 of this test. If Code 48 is not present, go to TEST KD, step 15.

    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 22 to step 25. No test procedures have been omitted.
  21. 25) Code 19: ISC RPM Low  Code 19 indicates that with ISC off, engine RPM dropped below self-test limit (about 600 RPM). Possible causes for this fault are:
    • Engine below normal operating temperature
    • Throttle body/air inlet contamination
    • Incorrect idle speed adjustment

    Turn key off and wait 10 seconds. Deactivate KOER SELF-TEST. Start and run engine at 2000 RPM for 2 minutes or until top radiator hose is hot and pressurized. Turn key off and wait 10 seconds. Rerun KOER SELF-TEST . If engine stumbles and/or Code 19 is still displayed, inspect throttle body and air inlet for contamination, service as necessary and adjust base idle. Rerun QUICK TEST PROCEDURES . If Code 19 has been cleared, service other codes as necessary.

  22. 26) Code 17: ISC RPM Low  Code 17 indicates that with the ISC off, engine RPM was below self-test limit. Possible causes for this fault are:
    • Excessive engine accessory load
    • Engine temperature below normal operating temperature
    • Throttle body/air inlet contamination
    • Incorrect idle adjustment

    Check and correct excessive engine load conditions, cooling fans, lights, etc. Run engine at 2000 RPM for 2 minutes, or until top radiator hose is hot and pressurized. Turn key off and wait 10 seconds. Rerun KOER SELF-TEST . If Code 17 is displayed, inspect throttle body and air inlet for contamination and clean as necessary. If okay, adjust base/curb idle speed and repeat QUICK TEST PROCEDURES . If Code 17 is not displayed, service other codes as necessary.

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