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Diagnostic Aids

Perform this test when instructed during QUICK TEST or if directed by other test procedures. This test is used to diagnose the following:

    NOTE: If directed here for a part throttle engine running problem, go to step  4).

  1. 1) Check For Incorrect Idle Speed
    Ensure engine is at normal operating temperature. Start engine and allow to idle for one minute. Using vehicle tachometer to read engine RPM or using scan tool, access RPM PID and check idle speed. See PIN VOLTAGE/PID VALUE TABLES in PIN VOLTAGE/PID VALUE CHARTS article. If idle speed is correct, turn ignition switch to OFF position and go to next step. If idle speed is high, ensure throttle arm fully returns and contacts return stop. Repair as necessary and go to step  6). For other idle speed problems, go to step  7).

  2. 2) Check For Sticking Or Binding Accelerator Linkage Problem

    Manually operate throttle from fully open to fully closed. Check for binding or sticking. If linkage sticks, binds or grabs, go to next step. If linkage does not stick, bind or grab, go to step  4).

  3. 3) Isolate Sticking Or Binding Problem

    Turn ignition switch to OFF position. Disconnect accelerator and speed control cables from throttle body. Check operation of throttle body by rotating throttle body linkage. If throttle body linkage moves freely, replace control cables. If throttle body linkage does not move freely, replace throttle body.

  4. 4) Check Functionality Of Throttle Position Sensor

    Connect scan tool to Data Link Connector (DLC). Turn ignition switch to ON position. Using scan tool, select TP V PID from PID/DATA MONITOR & RECORD menu. Monitor TP V PID voltage reading while slowly depressing accelerator pedal from closed throttle position to Wide Open Throttle (WOT) position. If TP V PID voltage reading is smooth during accelerator movement, go to next step. If TP V PID voltage reading is not smooth during accelerator movement, replace TP sensor.

  5. 5) Check Air Filter & Inlet For Restrictions

    Check air filter and inlet tube for restrictions. Check for plugging or blockage through air inlet to throttle body. Clean inlet and filter or replace filter as necessary. If air filter and inlet tube are okay, go to next step.

  6. 6) Check For Positive Crankcase Ventilation Problem

    A high idle may indicate incorrect PCV valve size or a vacuum leak. Check PCV valve connections for leaks or cracks. Remove PCV valve and check for plugged or incorrect valve. Repair as necessary. If PCV valve is okay, reinstall PCV valve and go to step  9) for high idle problems, or go to next step for all others.

  7. 7) Check IAC Solenoid Function

    Reconnect PCV valve if disconnected previously. Ensure all accessories are off. Ensure engine is at operating temperature. Start engine and allow to idle for one minute. Disconnect IAC solenoid harness connector. If engine idle speed decreases or engine almost stalls, go to next step. If engine idle speed is low and does not change when disconnecting IAC solenoid, replace IAC solenoid. If engine idle speed is high and does not change when disconnecting IAC solenoid, go to step  9).
    8. NOTE: Not all applications have a throttle plate hole. If not equipped, go to SYMPTOMS in TROUBLE SHOOTING - NO CODES article.

  8. 8) Check Throttle Body Plate Hole For Plugging
    Remove resonator from throttle body assembly. Inspect throttle plate hole for restriction. Repair as necessary. If throttle plate hole is not restricted, go to SYMPTOMS in TROUBLE SHOOTING - NO CODES article and diagnose by symptom.

  9. 9) Check For Vacuum Leaks

    Start engine and allow to idle. Listen for vacuum leaks. Inspect inlet air system from Mass Airflow (MAF) sensor to intake manifold for cracks, loose connections or faulty gaskets. Inspect intake manifold, EGR diaphragm, seal to intake manifold and vacuum hoses for leaks. Repair as necessary. If no faults are found, disconnect IAC valve harness connector. If idle speed does not drop, replace IAC valve. If idle speed drops, go to next step.

  10. 10) Check Throttle Body For Excessive Wear

    Turn ignition switch to OFF position. Remove throttle body. With throttle fully closed, hold throttle body up to light source. Check for excessive gap between throttle bore and plate. Rotate throttle lever to WOT and inspect bore for wear or grooving. If faults are present, replace throttle body. If throttle body is okay, fault cannot be duplicated or identified at this time. Reinstall throttle body and go to SYMPTOMS in TROUBLE SHOOTING - NO CODES article and diagnose by symptom.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 10) to step 15). No test procedures have been omitted.
    11. NOTE: Intake Manifold Runner Control (IMRC), Intake Manifold Swirl Control (IMSC) and Swirl Control Valve Monitor (SCVM) will be referred to as IMRC, IMSC or SCVM throughout diagnostic procedures. See Fig 2.
    WARNING: Be careful when operating IMRC or IMSC by hand. IMRC or IMSC return springs are strong and cause plates to close suddenly.

  11. 15) DTC P1512, P1513, P1516-P1520, P1537 Or P1538
    DTCs P1512, P1513 and P1519 indicate IMRC or IMSC may be stuck closed. KOEO or Continuous Memory self-test failed when IMRC or IMSC monitor circuit signal exceeded expected calibrated range with IMRC or IMSC activated. Possible causes are:
    • Faulty Vacuum Hoses
    • Faulty Vacuum Solenoid
    • Faulty Vacuum Actuator
    • IMRC Or IMSC Actuator Cable, Lever Or Gears Binding Or Seized
    • Cables Improperly Routed, Binding Or Seized
    • Faulty IMRC Or IMSC Actuator
    • Damaged Or Disconnected IMRC Or IMSC Housing Return Springs
    • Lever Return Stop Obstructed Or Bent
    • Lever Wide Open Stop Obstructed Or Bent
    • IMRC Or IMSC Monitor Circuit Open Or Shorted To VREF
    • IMRC Or IMSC SIG RTN Circuit Open Or Shorted To VPWR Or GND
    • IMRC Or IMSC VPWR Circuit Open

    DTCs P1516 (IMRC or IMSC input error bank No. 1) and P1517 (IMRC or IMSC input error bank No. 2) indicate KOEO or Continuous Memory self-test failed when IMRC or IMSC monitor circuit signal falls below or exceeds expected calibrated range. Possible cause is binding, seizing, damage or obstruction of IMRC or IMSC mechanical system.

    DTCs P1518, P1537 and P1538 may indicate IMRC or IMSC stuck open. KOEO or Continuous Memory self-test failed when IMRC or IMSC monitor circuit signal falls below expected calibrated range at closed throttle. Possible causes are:

    • IMRC Or IMSC SIG Circuit Shorted To PWR GND Or SIG RTN
    • Faulty IMRC Or IMSC Actuator
    • Faulty Powertrain Control Module (PCM)

    On models equipped with cable operated IMRC or IMSC, check IMRC or IMSC cables for correct routing and possible binding. Ensure cable core wire (if equipped) has slack at IMRC or IMSC housing and that lever contacts close plate stop screw. Ensure return springs operate properly and plates open and close fully. On models with vacuum operated systems, engine must run for 20 seconds then perform KOEO ON-DEMAND SELF-TEST. On all models, operate IMRC or IMSC plates at intake manifold while checking for binding and sticking. If any faults are found, go to next step. If no faults are found, go to step  17).

  12. 16) Perform IMRC Or IMSC Physical Test

    On B2300, remove actuator assembly. On all other models,disconnect IMRC or IMSC linkage or cable(s) from intake runner(s). Rotate IMRC or IMSC lever(s) to fully open and back to fully closed positions while checking for binding or sticking. Feel for return spring tension. Levers should fully open and close without obstruction. If any faults are found, clean or repair as necessary. If no faults are found, replace IMRC or IMSC actuator.

  13. 17) Perform IMRC or IMSC Functional Test

    Connect scan tool to Data Link Connector (DLC). Turn ignition switch to ON position. On B2300, monitor IMRCM or SCVM PID voltage. If IMRCM or SCVM PID voltage reading is less than one volt, go to step  23). On all other models, if IMRC or IMSC plates open immediately when ignition switch is turned to ON position, go to step  23). If IMRCM or SCVM PID voltage reading is one volt or more on B2300, or if IMRC or IMSC plates do not open immediately on all other models, use scan tool and access OUTPUT TEST MODE. See OUTPUT TEST MODE  under ADDITIONAL SYSTEM FUNCTIONS. Select START to turn all outputs ON. When IMRC or IMSC is commanded ON, lever(s) should rotate to full open position. One or both levers should contact wide open stop (one lever being slightly off is acceptable). On B2300, listen for IMRC or IMSC to actuate. On all models, IMRC or IMSC levers should cycle from fully closed and remain in fully open position while outputs are ON. If IMRC or IMSC levers do not operate as specified, go to next step. If IMRC or IMSC levers operate as specified, go to step  25).

  14. 18) Check IMRC Or IMSC Actuator VPWR Circuit For An Open In Harness

    Turn ignition switch to OFF position. Disconnect IMRC or IMSC actuator harness connector. Turn ignition switch to ON position. Using a DVOM, measure voltage of VPWR circuit between negative battery terminal and IMRC or IMSC actuator harness connector. See Fig 1 and Fig 2 . If voltage is more than 10.5 volts, go to step  20) for B2300, or go to next step for all other models. If voltage is 10.5 volts or less, repair open in VPWR circuit.
    Fig 1: Identifying IMSC Wiring Harness Connector Terminals (B2300)
    G00035656Courtesy of FORD MOTOR CO.
    Fig 2: Identifying SCVM Wiring Harness Connector Terminals (B2300)
    G00035657Courtesy of FORD MOTOR CO.

  15. 19) Check IMRC Or IMSC GND Circuits For Open In Harness

    Using a DVOM, measure voltage between IMRC or IMSC actuator harness connector GND circuits and VPWR circuit terminal. See Fig 1. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, repair open in affected GND circuit.

  16. 20) Verify Driver (SIG) Circuit Function

    Turn ignition switch to OFF position. Ensure scan tool is connected to DLC. Connect a test light between IMRC or IMSC actuator harness connector VPWR and IMRC or IMSC SIG circuit terminals. Test light should be off. Using scan tool, access OUTPUT TEST MODE. See OUTPUT TEST MODE  under ADDITIONAL SYSTEM FUNCTIONS. Select START to turn all outputs ON. If test light illuminates, go to step  32). If test light does not illuminate, go to next step.

  17. 21) Check For Open IMRC Or IMSC Driver (SIG) Circuit For Open In Harness

    Disconnect PCM connector(s). Using a DVOM, measure resistance of IMRC or IMSC SIG circuit between PCM harness connector and IMRC or IMSC actuator harness connector. See Fig 1. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in IMRC or IMSC SIG circuit.

  18. 22) Check IMRC Or IMSC Driver (SIG) Circuit For Short To VPWR In Harness

    Turn ignition switch to ON position. Using a DVOM, measure voltage between chassis ground and IMRC or IMSC actuator harness connector SIG circuit terminal. See Fig 1. If voltage is 10.5 volts or more, repair short to VPWR. If voltage is less than 10.5 volts, fault may be intermittent. Go to TEST Z, step  1). If no intermittent faults are found, replace PCM.

  19. 23) Check IMRC Or IMSC Driver (SIG) Circuit For Short To GND Or Monitor Circuit (PCM Connected)

    Turn ignition switch to OFF position. Using a DVOM, measure resistance between IMRC or IMSC actuator harness connector SIG circuit terminal and PWR GND, SIG RTN and IMRCM or SCVM (monitor) circuit terminals. See Fig 2. If all resistance measurements are more than 10 k/ohms, replace IMRC or IMSC actuator. If any resistance measurement is 10 k/ohms or less, go to next step.

  20. 24) Check IMRC Or IMSC Driver (SIG) Circuit For Short To GND Or Monitor Circuit (PCM Disconnected)

    Ensure ignition switch is turned to OFF position. Disconnect PCM connector(s). Using a DVOM, measure resistance between IMRC or IMSC actuator harness connector SIG circuit terminal and PWR GND, SIG RTN and IMRCM or SCVM circuit terminals. See Fig 2. If all resistance measurements are more than 10 k/ohms, replace PCM. If any resistance measurement is 10 k/ohms or less, repair short between affected circuits.

  21. 25) Check IMRCM Or SCVM PID To Determine Path For Possible Short

    Ensure ignition switch is turned to ON position. Using scan tool, select IMRCM or SCVM PID from PID/DATA MONITOR & RECORD menu. Voltage reading should be about 4.5 volts. If IMRCM or SCVM PID voltage reading is as specified, go to next step. If IMRCM or SCVM PID voltage reading is not as specified, go to step  30).

  22. 26) Check IMRCM Or SCVM PID To Determine A Short To VPWR

    Using scan tool, access OUTPUT TEST MODE. See OUTPUT TEST MODE  under ADDITIONAL SYSTEM FUNCTIONS. Select IMRCM or SCVM PID from PID/DATA MONITOR & RECORD menu. Select START to turn all outputs ON. If IMRCM or SCVM PID voltage reading is less than one volt, go to next step. If IMRCM or SCVM PID voltage reading is one volt or more, go to step  32).

  23. 27) Check IMRCM or SCVM Circuit For Short To VPWR At Harness Connector

    Disconnect IMRC or SCVM harness connector. Turn ignition switch to ON position. Using a DVOM, measure voltage of IMRCM or SCVM circuit between chassis ground and IMRC or SCVM harness connector. See Fig 2. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, go to step  29).

  24. 28) Determine Short To PWR (PCM Disconnected)

    Turn ignition switch to OFF position. Disconnect PCM connector(s). Turn ignition switch to ON position. Using a DVOM, measure voltage between chassis ground and IMRC or SCVM harness connector IMRCM or SCVM terminal. If voltage is less than 10.5 volts, replace PCM. If voltage is 10.5 volts or more, repair short to PWR in IMRC or SCVM circuit.

  25. 29) Check Monitor For Short To VPWR At IMRC Or IMSC Actuator

    Turn ignition switch to OFF position. Using a DVOM, measure resistance between IMRC or SCVM harness connector VPWR and IMRCM or SCVM terminals. See Fig 2. If resistance is 10 k/ohms or less, replace IMRC or IMSC actuator. If resistance is more than 10 k/ohms, fault may be intermittent. Go to TEST Z, step  1). If no intermittent faults are found, replace PCM.

  26. 30) Check IMRCM Or SCVM Circuit For Short To Ground

    Ensure ignition switch is turned to ON position. Using scan tool, select IMRCM or SCVM PID from PID/DATA MONITOR & RECORD menu. Observe IMRCM or SCVM PID voltage reading while disconnecting IMRC or SCVM harness connector. If IMRCM or SCVM PID voltage reading changed from less than one volt to VREF voltage, replace IMRC or IMSC actuator. If voltage does not change from less than one volt to VREF voltage, go to next step.

  27. 31) Check IMRCM Or SCVM Circuit Harness For Short To Ground

    Turn ignition switch to OFF position. Disconnect PCM connector(s). Using a DVOM, measure resistance between IMRC or SCVM harness connector IMRCM or SCVM and SIG RTN circuit terminals, and between IMRCM or SCVM terminal and chassis ground. See Fig 2. If resistance is more than 10 k/ohms, replace PCM. If resistance is 10 k/ohms or less, repair short to SIG RTN or chassis ground in IMRCM or SCVM circuit.

  28. 32) Check IMRCM Or SCVM Circuit Response

    Turn ignition switch to OFF position. Disconnect IMRC or SCVM harness connector. Ensure scan tool is connected to DLC. Turn ignition switch to ON position. Using scan tool, select IMRCM or SCVM PID from PID/DATA MONITOR & RECORD menu. Observe IMRCM or SCVM PID voltage reading while connecting a jumper wire between chassis ground and IMRC or SCVM harness connector IMRCM or SCVM terminal. See Fig 2. If IMRCM or SCVM PID voltage reading cycled from VREF voltage to less than one volt, go to next step. If IMRCM or SCVM PID voltage reading does not change from VREF voltage to less than one volt, go to step  36).

  29. 33) Check SIG RTN Or Chassis GND Circuit Continuity (PCM Connected)

    Turn ignition switch to OFF position. Reconnect PCM harness connector(s). Using a DVOM, measure resistance between negative battery terminal and IMRC or SCVM harness connector SIG RTN or chassis GND circuit terminal. See Fig 2. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, go to step  35).

  30. 34) Check IMRCM Or SCVM Circuit For Intermittent Open

    Ensure ignition switch is turned to OFF position. Using a DVOM, measure resistance of IMRCM or SCVM circuit between PCM harness connector and IMRC or SCVM harness connector. Wiggle and bend wiring harness between IMRC or SCVM harness connector and PCM harness connector. A fault will be indicated by a change in resistance measurement. If fault is indicated, isolate fault and repair as necessary. If no faults are indicated, replace IMRC or IMSC actuator.

  31. 35) Check SIG RTN Or Chassis GND Circuit Continuity (PCM Disconnected)

    Disconnect PCM connector(s). Using a DVOM, measure resistance of SIG RTN or chassis GND circuit between IMRC or IMSC actuator harness connector and PCM harness connector. If resistance is 5 ohms or more, repair open in SIG RTN or chassis GND circuit. If resistance is less than 5 ohms, fault may be intermittent. Go to TEST Z, step  1). If no intermittent faults are found, replace PCM.

  32. 36) Check IMRCM Or SCVM Circuit Continuity

    Turn ignition switch to OFF position. Disconnect PCM connector(s). Using a DVOM, measure resistance of IMRCM or SCVM circuit between PCM harness connector and IMRC or SCVM harness connector and PCM harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in IMRCM or SCVM circuit.

  33. 37) Check IMRCM Or SCVM Circuit For Intermittent Open

    Ensure ignition switch is turned to OFF position. Using a DVOM, measure resistance of IMRCM or SCVM circuit between PCM harness connector and IMRC or IMSC actuator harness connector while wiggling wiring harness between IMRC or IMSC actuator connector and PCM harness connector. A fault will be indicated by change in resistance measurement. If fault is indicated, isolate fault and repair as necessary. If no faults are indicated, replace PCM.

  34. 38) IMRC Or IMSC Repair Verification Drive Cycle

    Connect scan tool to Data Link Connector (DLC). Turn ignition switch to ON position. Perform PCM RESET PROCEDURE  under CLEARING CODES under SELF-DIAGNOSTIC SYSTEM. Using scan tool, access appropriate IMRC or IMSC, and IMRCM or SCVM PIDs. Test drive vehicle. Complete 3 accelerations from a complete stop to a speed requiring engine speed of more than 3500 RPM. Observe PID voltage reading changes. Stop vehicle. Perform QUICK TEST  and retrieve all DTCs. If any DTCs are present, go to appropriate system test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are present, testing is complete.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 38) to step 65). No test procedures have been omitted.

  35. 65) KOEO & Continuous Memory DTC P1549: Perform Visual Inspection

    DTC P1549 indicates Intake Manifold Tuning Valve (IMTV) monitor failed during KOEO or Conitnuous Memory self-test when PCM detected a problem with IMTV output circuit. Possible causes are:
    • VPWR Circuit Open
    • Open Or Shorted IMTV SIG Circuit
    • Faulty IMTV
    • Faulty Powertrain Control Module (PCM)

    Turn ignition switch to OFF position. Check IMTV system. Ensure harness connector is installed properly. Repair as necessary. If no faults are found, go to next step.

    36. NOTE: Vehicle must be driven if rev limiter does not allow engine speed to exceed 3500 RPM while performing this step.

  36. 66) Check PCM Driver Command
    Connect scan tool to Data Link Connector (DLC). Start engine and allow to idle. Using scan tool, access IMTV PID from PID/DATA MONITOR & RECORD menu. Observe IMTV PID value while increasing engine speed slowly to about 4000 RPM. IMTV PID value should indicate 100 percent then drop to 50 percent when engine RPM is more than 3500. If IMTV PID value operates as specified, PCM driver command is okay. Go to next step. If IMTV PID value does not operate as specified, replace PCM.

  37. 67) Check IMTV Actuator VPWR Circuit For Open In Harness

    Turn ignition switch to OFF position. Disconnect IMTV actuator harness connector. Turn ignition switch to ON position. Using a DVOM, measure voltage of VPWR circuit between negative battery terminal and IMTV actuator harness connector. If voltage is more than 10.5 volts, go to step  69). If voltage is 10.5 volts or less, repair open in VPWR circuit.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 67) to step 69). No test procedures have been omitted.

  38. 69) Check For Open IMTV SIG Circuit Between PCM & IMTV Actuator

    Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect for damaged terminals and repair if necessary. Using a DVOM, measure resistance of IMTV SIG circuit between PCM harness connector and IMTV actuator harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in IMTV SIG circuit.

  39. 70) Check IMTV Actuator Signal Circuit For Short To PWR GND

    Using a DVOM, measure resistance between PCM harness connector IMTV SIG circuit terminal and PWR GND circuit terminals. See PCM PWR GND, SIG RTN & VREF TERMINAL IDENTIFICATION  table. See Figure. If resistance is more than 10 k/ohms, go to next step. If resistance is 10 k/ohms or less, repair short between IMTV SIG and PWR GND circuit(s).

  40. 71) Check IMTV SIG Circuit For Short To VPWR

    Turn ignition switch to ON position. Using a DVOM, measure voltage between PCM harness connector IMTV SIG and VPWR circuit terminals. See WIRING DIAGRAMS article. See Figure. If voltage is one volt or more, repair short between IMTV SIG and VPWR circuit(s). If voltage is less than one volt, go to next step.

  41. 72) Check PCM Driver For IMTV Actuator

    Turn ignition switch to OFF position. Reconnect PCM harness connector. Connect scan tool to Data Link Connector (DLC). Connect a test light between negative battery terminal and IMTV actuator harness connector VPWR terminal. Turn ignition switch to ON position. Using scan tool, access OUTPUT TEST MODE. See OUTPUT TEST MODE  under ADDITIONAL SYSTEM FUNCTIONS. Command all outputs ON. If test light was off with all outputs OFF and illuminates with all outputs ON, go to next step. If test light does not operate as specified, replace PCM. Verify symptom is no longer present.

  42. 73) Check IMTV Shutter For Damage

    Remove IMTV. Check IMTV shutter for damage. Rotate shutter and check for binding. Replace IMTV as necessary. Verify symptom is no longer present. If IMTV is okay, leave IMTV disassembled and go to next step.

  43. 74) Check IMTV Actuator For Coil Damage

    Reconnect IMTV actuator harness connector. Turn ignition switch to ON position. Using scan tool, access OUTPUT TEST MODE. See OUTPUT TEST MODE  under ADDITIONAL SYSTEM FUNCTIONS. Observe IMTV shutter while turning all outputs ON. If shutter rotates, fault may be intermittent. Go to TEST Z, step  1). If shutter does not rotate, replace IMTV actuator. Verify symptom is no longer present.
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