Diagnostic Aids

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

• TP sensor.
• Harness circuits: SIG RTN, TP and VREF.
• Powertrain Control Module (PCM).

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.

1. 1) DTC P0120
   
   DTC P0120 indicates TP circuit malfunction. Possible causes for this fault are:
   • Binding throttle shaft or linkage.
   • Faulty TP sensor.
   • TP sensor or throttle stop adjustment.
   • 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 fuse panel DLC. Turn ignition on. Access TP PID. If TP PID is 0.35-4.60 volts, go to step  30). If voltage is less than 0.35 volt, go to next step. If voltage is greater than 4.60 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
   
   Disconnect TP sensor. Turn ignition on. Measure voltage between VREF (Brown wire) and SIG RTN (Black/Yellow wire) terminals at TP sensor harness connector. See Fig 1. Also see CIRCUIT PIN IDENTIFICATION  table. If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, reconnect sensor and go to TEST C .
   Fig 1: Identifying TP Sensor Circuit & Harness Connector Terminals

   Courtesy of FORD MOTOR CO.
4. 11) Simulate High TP Signal
   
   With TP sensor disconnected, connect a jumper wire between TP (Red wire) and VREF (Brown wire) terminals at TP sensor harness connector. Connect NGS scan tool to fuse panel 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 Circuit Continuity
   
   Turn ignition off. Inspect PCM connector for pushed out pins, corrosion, loose wires, etc. Disconnect TP sensor. Measure resistance of Red wire circuit between TP sensor connector and PCM connector terminal No. 23. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit. Repeat QUICK TEST .
6. 13) Check TP Circuit For Short To Ground
   
   Leave TP sensor disconnected. Ensure PCM is disconnected. Measure resistance between PCM connector TP terminal No. 23 (Red wire) and SIG RTN terminal No. 58 (Black/Yellow wire) and GND terminal No. 96 (Black wire). If all resistance measurements are 10 k/ohms or more, replace PCM and repeat QUICK TEST . If any resistance measurement is less than 10 k/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 jumper wire between TP signal (Red wire) and SIG RTN (Black/Yellow wire) terminals at TP sensor harness connector. See Fig 1. Also see CIRCUIT PIN IDENTIFICATION  table. Connect NGS scan tool to fuse panel DLC. Turn ignition on. Access TP PID. If TP PID is greater than 0.2 volt, remove jumper wire and 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. Disconnect PCM. Disconnect TP sensor. Measure resistance between TP terminal (Red wire) at TP sensor connector and PCM connector terminal No. 23. Also measure resistance between SIG RTN terminal (Black/Yellow wire) at TP sensor connector and PCM connector terminal No. 58. 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 and PCM disconnected. Measure resistance between PCM connector terminals No. 23 (Red wire) and No. 57 (Brown wire). If resistance is 10 k/ohms or more, replace PCM. Reconnect all electrical connections and repeat QUICK TEST . If resistance is less than 10 k/ohms, repair short to VREF circuit. Restore all electrical connections 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 fuse panel 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 TEST Z  or TROUBLE SHOOTING - NO CODES - VILLAGER article.
    THROTTLE POSITION SENSOR OUTPUT
    
    

    Throttle Position	Volts
    Closed	.4
    1/4	1.3
    Half Open	2.2
    3/4	3.1
    Fully Open	4.1