Diagnostic Aids

Perform this test only when directed by QUICK TEST. This test is intended to diagnose the following:

• TP sensor.
• Idle (IDL) switch.
• Wiring harness circuits (IDL, SIG RTN, TP and VREF).
• Powertrain Control Module (PCM).

Normal range of throttle angle measurement for TP sensor is 0-85 degrees. To pass QUICK TEST procedure, range of throttle rotation (in degrees) must be within 3 percent of specification.

To prevent replacement of good components, be aware the following non-EEC related areas may be at fault:

• Idle speed.
• Binding throttle shaft or linkage.
• TP sensor not seated.

Fig 1: Identifying TP Sensor Circuit & Connector Terminals

1. 1) DTC P0120  DTC P0120 indicates TP circuit may be out of range. Possible causes for this fault are:
   • Binding throttle shaft or linkage.
   • Faulty TP sensor.
   • Open or short in harness.
   • Faulty Powertrain Control Module (PCM).

   If throttle plate binds, repair and repeat QUICK TEST. If throttle plate and linkage is okay, go to next step.

2. 2) Check TP PID  Turn ignition off. Connect NGS scan tool to OBD-II DLC. Turn ignition on. Access TP PID. If TP PID is between 0.4-4.3 volts, go to step 30). If voltage is less than 0.4 volt, go to next step. If voltage is greater than 4.3 volts, go to step 20).
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 2) to step 10). No test procedures have been omitted.
3. 10) Check VREF Circuit Voltage  With TP sensor disconnected, turn ignition on. Measure voltage between VREF and SIG RTN terminals at TP sensor wiring harness connector. If voltage is greater than 4.5 volts, go to next step. If voltage is 4.5 volts or less, reconnect sensor and go to CIRCUIT TEST C .
4. 11) Simulate High TP Signal  Disconnect TP sensor. Connect a jumper wire between TP signal and VREF terminals at TP sensor harness connector. Connect NGS scan tool to OBD-II DLC. Turn ignition on. Access TP PID. If TP PID is less than 4.5 volts, go to next step. If TP PID is greater than 4.5 volts, replace TP sensor. Restore all electrical connections and repeat QUICK TEST.
5. 12) Check TP & SIG RTN Circuit Continuity  Turn ignition off. Inspect PCM connector for pushed out pins, corrosion, loose wires, etc. Install breakout box (leave PCM disconnected). Disconnect TP sensor. Measure resistance between TP terminal at TP sensor connector and breakout box test pin TP. Also measure resistance of SIG RTN circuit between sensor connector SIG RTN terminal and breakout box test pin SIG RTN. If both resistance measurements are less than 5 ohms, go to next step. If either resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST.
6. 13) Check TP Circuit For Short To Ground  Leave TP sensor disconnected and breakout box installed. Measure resistance between test pin TP and test pin SIG RTN and GND. If all resistance measurements are 10,000 ohms or more, replace TP sensor and repeat QUICK TEST. If any resistance measurement is less than 10,000 ohms, repair short circuit and repeat QUICK TEST.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 13) to step 20). No test procedures have been omitted.
7. 20) Simulate Low TP Signal  Turn ignition off. Disconnect TP sensor. Connect a jumper wire between TP signal and SIG RTN terminals at TP sensor harness connector. Connect NGS scan tool to OBD-II DLC. Turn ignition on. Access TP PID. If TP PID is greater than 0.2 volt, go to next step. If TP PID is less than 0.2 volt, replace TP sensor. Restore all electrical connections and repeat QUICK TEST.
8. 21) Check TP & SIG RTN Circuit Continuity  Turn ignition off. Inspect PCM connector for pushed out pins, corrosion, loose wires, etc. Install breakout box (leave PCM disconnected). Disconnect TP sensor. Measure resistance between TP terminal at TP sensor connector and breakout box test pin TP. Also measure resistance of SIG RTN circuit between TP sensor connector SIG RTN terminal and breakout box test pin SIG RTN. If both resistance measurements are less than 5 ohms, go to next step. If either resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST.
9. 22) Check TP Circuit For Short To VREF  Turn ignition off. Leave TP sensor disconnected and breakout box installed (PCM disconnected). Measure resistance between test pin TP and test pin VREF. If resistance is 10,000 ohms or more, replace TP sensor and repeat QUICK TEST. If resistance is less than 10,000 ohms, repair short circuit and repeat QUICK TEST.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 22) to step 30). No test procedures have been omitted.
10. 30) Check TP Sensor Signal To PCM  Turn ignition off. Connect NGS scan tool to OBD-II DLC. Turn ignition on. Access TP PID. While slowly opening throttle, observe TP PID value and compare with THROTTLE POSITION SENSOR OUTPUT table. If voltage is not as specified, replace TP sensor and repeat QUICK TEST. If voltage is as specified, fault may be intermittent. Go to CIRCUIT TEST Z  or TESTS W/O CODES - 2.5L article.
    THROTTLE POSITION SENSOR OUTPUT
    
    

    Throttle Position	Voltage
    Closed	.5
    1/4	1.3
    Half Open	2.2
    3/4	2.9
    Fully Open	3.7

    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 30) to step 40). No test procedures have been omitted.
11. 40) DTC P0510: Idle Switch Fault  DTC P0510 indicates idle (IDL) switch or circuit fault. Possible causes for this fault are as follows:
    • Faulty IDL switch (integrated with throttle position sensor).
    • Open or short in harness.
    • Faulty PCM.

    Turn ignition off. Connect NGS scan tool to OBD-II DLC. Turn ignition on. Access IDL SW PID. Observe PID value while depressing and releasing throttle. PID should indicate IDL SW ON with accelerator pedal released, and OFF with accelerator pedal depressed. If idle switch operates as specified, fault is intermittent. Go to CIRCUIT TEST Z  or TESTS W/O CODES - 2.5L article. If idle switch does not operate as specified, go to next step.

12. 41) Check Idle Switch Circuit At PCM  Turn ignition off. Install breakout box. Leave PCM disconnected. Inspect PCM connector for pushed out pins, corrosion, loose wires, etc. Measure voltage between breakout box test pin IDL and test pin SIG RTN while depressing accelerator pedal. If voltage is less than one volt with accelerator pedal released and greater than 10 volts with accelerator pedal depressed, replace PCM. Restore wiring connections and repeat QUICK TEST. If voltage is not as specified, go to next step.
13. 42) Check IDL & SIG RTN Circuit Continuity  Turn ignition off. Install breakout box. Leave PCM disconnected. Inspect PCM connector for pushed out pins, corrosion, loose wires, etc. Disconnect idle switch connector (TP sensor connector). Measure resistance between IDL terminal at sensor harness connector and breakout box test pin IDL. Also measure resistance between SIG RTN terminal at sensor connector and breakout box test pin SIG RTN. If both resistance measurements are less than 5 ohms, go to next step. If either resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST.
14. 43) Check IDL Circuit For Short To Ground  Disconnect idle switch (TP sensor) connector. With breakout box installed (PCM disconnected), measure resistance between test pin IDL and test pin SIG RTN. Also measure resistance between breakout box test pin IDL and GND. If all resistance measurements are 10,000 ohms or more, go to next step. If any resistance measurement is less than 10,000 ohms, repair short circuit and repeat QUICK TEST.
15. 44) Check Circuit For Short To Power  Turn ignition off. Leave breakout box installed (PCM disconnected). Turn ignition on. Measure voltage between breakout box test pin IDL and GND. If voltage is greater than one volt, repair short to power in IDL circuit. Restore electrical connections and repeat QUICK TEST. If voltage measurement is less than one volt, replace TP sensor (includes idle switch). Restore electrical connections and repeat QUICK TEST.