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Diagnostic Aids

WARNING: This page is about a different variant/trim than selected.

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

Fig 1: TA System Circuits & System Components
G95C12601
Fig 2: TP-B Operational Range
G95D12602
Fig 3: TA System Connectors & Test Circuits
G95E12603
  1. 1) DTC P0222: Verify TP-B Voltage  This DTC indicates TP-B voltage was below minimum during self-test. Possible causes are as follows:
    • Open or shorted TP-B circuit.
    • Open or shorted VREF circuit.
    • Faulty TP-B.
    • Faulty PCM.

    Turn ignition off. Connect scan tester to Data Link Connector (DLC). Turn ignition on. Using scan tester, access TPB PID. If TPB PID voltage is less than 0.2 volts, go to next step. If TPB PID voltage is 0.2 volt or more, go to step 6).

  2. 2)  Turn ignition off. Disconnect TP-B wiring harness connector. Inspect connector for damage and repair if necessary. Connect jumper wire between connector terminals TP-B (Yellow/White wire) and VREF (Brown/White wire). Turn ignition on. Using scan tester, access TPB PID. If PID cannot be accessed, go to step 5). If PID voltage is 4-6 volts, replace TP-B and repeat QUICK TEST . If voltage is not 4-6 volts, go to next step.
  3. 3)  Leave TP-B disconnected. Turn ignition on. Measure voltage between connector terminals SIG RTN (Gray/Red wire) and VREF (Brown/White wire). If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, go to CIRCUIT TEST C.
  4. 4) Check TP-B For Open Circuit  Turn ignition off. Disconnect PCM 104-pin connector. Inspect pins for damage and repair if necessary. Install EEC-V Breakout Box (014-000950), leaving PCM disconnected. Measure resistance between test pin No. 63 (TP-B) at the breakout box and TP-B (Yellow/White wire) terminal of TP-B wiring harness connector. If resistance is 5 ohms or more, repair open in TP-B circuit and repeat QUICK TEST . If resistance is less than 5 ohms, go to next step.
  5. 5) Check TP-B Circuit For Short To Ground Or SIG RTN  Turn ignition off. Measure resistance between test pin No. 63 (TP-B) and test pins No. 51, 91 and 103 (PWR GND) at the breakout box. If resistance 10,000 ohms or more, replace PCM and repeat QUICK TEST . If resistance is less than 10,00 ohms, repair TP-B circuit short to ground or SIG RTN and repeat QUICK TEST .
  6. 6) Wiggle Test  Turn ignition on. Using scan tester, access TPB PID. Observe PID for signs of fault. A fault will be indicated by change in PID voltage. Lightly tap on sensor. Wiggle wiring harness between TP-B and PCM. If fault is indicated, isolate and repair as necessary. If no faults are indicated, go to CIRCUIT TEST Z.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 6) to step 10). No test procedures have been omitted.
  7. 10) DTC P0222: Verify TP-B Voltage  This DTC indicates TP-B voltage was above maximum during self-test. Possible causes are as follows:
    • TP-B circuit shorted to VREF.
    • TP-B circuit shorted to PWR.
    • SIG RTN circuit open.
    • Faulty TP-B.
    • Faulty PCM.

    Turn ignition off. Disconnect TP-B wiring harness connector. Connect scan tester to Data Link Connector (DLC). Turn ignition on. Using scan tester, access TPB PID. If PID voltage is more than 4 volts, go to next step. If voltage is 4 volts or less, go to step 16).

  8. 11) Check TP-B For Short To Power  Turn ignition off. Disconnect TP-B sensor wiring harness connector. Inspect connector for damage and repair if necessary. Turn ignition on. Measure voltage between connector terminal TP-B (Yellow/White wire) and negative battery terminal. If voltage is 10.5 volts or more, go to next step. If voltage is less than 10.5 volts, go to step 13).
  9. 12)  Turn ignition off. Disconnect PCM 104-pin connector. Inspect pins for damage and repair if necessary. Install EEC-V Breakout Box (014-000950), leaving PCM disconnected. Turn ignition on. Measure voltage between test pin No. 63 (TP-B) and test pins No. 51 and 103 (PWR GND) at the breakout box. If voltage is 10.5 volts or more, repair short between PWR and TP-B circuit. Repeat QUICK TEST . If voltage is less than 10.5 volts, replace PCM and repeat QUICK TEST .
  10. 13)  Turn ignition off. Leave TP-B wiring harness connector disconnected. Turn ignition on. Using scan tester, access TPB PID. If PID voltage is less than 0.1 volt, go to next step. If voltage is 0.1 volt or more, go to step 15).
  11. 14)  Leave TP-B disconnected and ignition on. Measure voltage between connector terminals SIG RTN (Gray/Red wire) and VREF (Brown/White wire). If voltage is 4-6 volts, replace TP-B and repeat QUICK TEST . If voltage is not 4-6 volts, perform procedures under CIRCUIT TEST C.
  12. 15) Check TP-B Circuit For Short To VREF  Leave TP-B disconnected and ignition on. Measure resistance between test pin No. 63 (TP-B) and 90 (VREF) at the breakout box. If resistance is 10,000 ohms or more, replace PCM and repeat QUICK TEST . If resistance is less than 10,000 ohms, repair TP-B circuit short to VREF and repeat QUICK TEST .
  13. 16) Wiggle Test  Turn ignition on. Using scan tester, access TPB PID. Observe PID for signs of fault. A fault will be indicated by change in PID voltage. Lightly tap on sensor. Wiggle wiring harness between TP-B and PCM. If fault is indicated, isolate and repair as necessary. If no faults are indicated, go to CIRCUIT TEST Z.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 16) to step 20). No test procedures have been omitted.
  14. 20) DTC P1220: Inspect Series Throttle (ST) System  This DTC indicates series throttle control malfunctioned during self-test. Possible causes are as follows:
    • Stepper motor circuit fault.
    • PWR GND circuit open to Series Throttle Controller (STC).
    • SIG RTN circuit open to STC.
    • VPWR circuit open to STC.
    • TAPW circuit open or shorted.
    • Faulty Series Throttle (ST).
    • Faulty ST stepper motor.
    • Faulty STC.
    • Faulty PCM.

    Turn ignition off. Remove air tube from ST. Inspect ST assembly for loose components or restrictions. Check throttle plate for binding. If throttle plate binds, go to next step. If throttle does not bind, go to step 22).

  15. 21) Inspect ST Motor  Turn ignition off. Remove TA assembly (DO NOT  separate ST from main throttle body). Remove ST stepper motor. Cycle throttle plate through full range of travel. Throttle plate should travel freely and throttle gear should contact stop screws in both directions. If throttle plate binds, replace ST stepper motor and repeat QUICK TEST . If throttle does not bind, replace series throttle and repeat QUICK TEST .
  16. 22)  Turn ignition on. Using scan tester, access TPB PID. If PID voltage is less than 4.5 volts, go to next step. If voltage is 4.5 volts or more, go to step 33).
  17. 23) Measure ST Stepper Motor Coil Resistance  Turn ignition off. Disconnect ST stepper motor wiring harness connector. Check for 1-5 ohms resistance at the following ST stepper motor terminals:
    • TA-B1 and BCOMM.
    • TA-B2 and BCOMM.
    • TA-A1 and ACOMM.
    • TA-A2 and ACOMM.

    If each coil measurement 1-5 ohms, go to next step. If any measurement is not 1-5 ohms, replace ST stepper motor and repeat QUICK TEST .

    Fig 4: Stepper Motor Terminals
    G95F12604
  18. 24) Check ST Stepper Motor Coil For Short Circuit  Leave ignition off and ST stepper motor disconnected. Measure resistance between ST stepper motor terminals ACOMM and BCOMM. Measure resistance between ST stepper motor terminals ACOMM/BCOMM and motor housing. If either resistance measurement is 10,000 ohms or less, replace ST stepper motor and repeat QUICK TEST . If all resistance measurements are 10,000 ohms or more and DTC P1220 is present, go to next step. If DTC P1220 is not present, check brake system mechanical components for malfunction and repair as necessary.
  19. 25) Check ST Stepper Motor Circuit Continuity  Leave ignition off and ST stepper motor disconnected. Disconnect Series Throttle Controller (STC). Measure resistance of each circuit between ST stepper motor connector and STC connector. If any resistance measurement is 5 ohms or more, repair open circuit and repeat QUICK TEST . If all resistance measurements are less than 5 ohms, go to next step.
  20. 26) Check ST Stepper Motor Circuit For Short  Leave ignition off. Disconnect scan tester from DLC (if applicable). Measure resistance of each terminal of ST stepper motor connector and all other terminals of ST stepper motor connector. Measure resistance of each terminal of ST stepper motor connector and negative battery terminals. If all resistance measurements are 10,000 ohms or more, go to next step. If any resistance measurements is 10,000 ohms or less, go to next step.
  21. 27) Check Circuit Voltage To STC  Leave STC disconnected. Turn ignition on. Measure voltage between VPWR terminal of STC connector and chassis ground. If voltage is 10.5 volts or more, go to next step. If voltage is less than 10.5 volts, repair open in VPWR circuit and repeat QUICK TEST .
  22. 28)  Turn ignition off. Leave STC disconnected. Measure resistance between SIG RTN terminal of STC connector and chassis ground. Measure resistance between PWR GND terminal of STC connector and chassis ground. If both resistance measurements are less than 5 ohms, go to next step. If either resistance measurements are 5 ohms or more, repair open circuit and repeat QUICK TEST .
  23. 29)  Leave ignition off and STC disconnected. Disconnect PCM 104-pin connector. Inspect pins for damage and repair if necessary. Install EEC-V Breakout Box (014-000950), leaving PCM disconnected. Measure resistance between test pin No. 18 (TAPW) and TAPW terminal of STC wiring harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in TAPW circuit and repeat QUICK TEST .
  24. 30)  Leave STC disconnected. Measure voltage between test pin No. 18 and negative battery terminal. If voltage is less than .05 volt, go to next step. If voltage is .05 volt or more, repair TAPW circuit short to power and repeat QUICK TEST .
  25. 31)  Turn ignition off. Leave STC disconnected. Measure resistance between test pin No. 18 (TAPW) and test pins No. 51, 91 and 103 at the breakout box. If resistance is less than 10,000 ohms, repair short circuit and repeat QUICK TEST . If resistance is 10,000 ohms or more and DTC P1220 is present, go to next step. If resistance 10,000 ohms or more and DTC P1220 is not present, fault intermittent and cannot be duplicated at this time. Go to CIRCUIT TEST Z.
    NOTE: On every power-up, the series throttle is commanded to self-test from the PCM. To verify this signal, go to next step.
  26. 32)  Leave ignition off and STC disconnected. Connect DVOM between test pin No. 18 (TAPW) and 91 (SIG RTN) at the breakout box. While observing DVOM, turn ignition on. If DVOM indicates a brief change of voltage (2.0 volt minimum) as ignition is turned on, replace STC and repeat QUICK TEST . If DVOM does not indicate a brief change of voltage, replace PCM and repeat QUICK TEST .
  27. 33)  Leave ignition on. Disconnect TP-B sensor wiring harness connector. Measure voltage between connector terminals SIG RTN (Gray/Red wire) and VREF (Brown/White wire). If voltage is 4-6 volts, replace TP-B and repeat QUICK TEST . If voltage is not 4-6 volts, see procedures under CIRCUIT TEST C.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 33) to step 40). No test procedures have been omitted.
  28. 40) DTC P1224: Check ST Assembly  This DTC should be disregarded if any other DTCs are present. DTC P1224 indicates TP-B voltage was out of range during self-test. Possible causes are as follows:
    • TP-B sensor binding or sticking.
    • Throttle stop screw misadjusted.
    • Faulty TP-B.
    • Faulty ST.

    Check throttle linkage for binding or sticking. Repair if necessary. If throttle linkage is okay, go to next step.

  29. 41)  Turn ignition off. Disconnect air tube from ST assembly. Connect scan tester to Data Link Connector (DLC). Turn ignition on. Using scan tester, access TPB PID. While observing PID voltage, push throttle plate shut and then release. Throttle plate should not bind or stick. If TPB-PID is 0.3-0.9 volt at wide open throttle, go to next step. If TPB-PID is not 0.3-0.9 volt at wide open throttle, check ST stepper motor and TP-B for damage. If no damage is present, replace TP-B and repeat QUICK TEST .
  30. 42)  Turn ignition off. Disconnect TP-B wiring harness connector. Inspect connector for damage and repair if necessary. Turn ignition on. Measure voltage between SIG RTN and VREF terminal of TP-B wiring harness connector. If voltage is 4-6 volts, replace TP-B and repeat QUICK TEST . If voltage is not 4-6 volts, go to CIRCUIT TEST C.
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