Diagnostic Aids

Enter this test only when all steps under QUICK TEST have been successfully completed and engine still does not start or if directed here from another test or chart. This test is only intended to diagnose:

• FTT sensor.
• FTT and FTT ground (FTT GND) circuits.
• Compuvalve.

1. 1) Check FTT Sensor Connector For Damage
   
   Turn ignition switch to OFF position. Check FTT sensor harness connector for damage and good connection. Repair or replace connector as necessary, then go to step  3). If FTT sensor harness connector is okay, go to next step.
NOTE: A non-functioning FTT sensor will give a constant reading of 59°F (15°C) on F150 and 32°F (0°C) on Contour.
2. 2) Check FTT Sensor PID Default
   Ensure ignition switch is turned to OFF position. With scan tool connected, turn ignition switch to ON position (engine off). Access FTTMP PID. If FTTMP PID is defaulted to 59°F (15°C) on F150 or 32°F (0°C) on Contour, replace FTT sensor. If FTTMP is not defaulted to 59°F (15°C) on F150 or 32°F (0°C) on Contour, go to next step.
3. 3) Check FTT PID Value
   
   With scan tool connected, turn ignition switch to ON position (engine off). Access FTTMP PID. If FTTMP PID value is more than -58°F (-50°C) for F150 CNG, more than -38°F (-39°C) for Contour and less than 140°F (60°C), system is operating normally, see INTERMITTENT TESTS . If FTTMP PID value is less than -58°F (-50°C) for F150 CNG, less than -38°F (-39°C) for Contour, go to next step. If FTTMP PID value is more than 140°F (60°C), go to step  5).
4. 4) Check FTT Sensor & Circuits For Short To Ground
   
   With scan tool connected, turn ignition switch to ON position (engine off). Access FTTMP PID. Disconnect FTT sensor connector. If FTTMP PID value is about 140°F (60°C), replace FTT sensor. If FTTMP PID value is not about 140°F (60°C), go to step  7).
5. 5) Check FTT Circuit For Open
   
   With scan tool connected, turn ignition switch to ON position (engine off). Access FTTMP PID. Disconnect FTT sensor connector. Connect a jumper wire between both FTT sensor harness connector terminals. If FTTMP PID value is about -58°F (-50°C) for F150 CNG or about -38°F (-39°C) for Contour, replace FTT sensor. If FTTMP PID value is more than 140°F (60°C), remove jumper wire and go to next step.
6. 6) Check FTT Circuit To Compuvalve For Open
   
   Turn ignition switch to OFF position. Ensure FTT sensor is disconnected. Disconnect compuvalve harness connector C4025. Measure resistance between specified compuvalve harness connector C4025 terminals and FTT sensor terminals. See COMPUVALVE TO FTT SENSOR OPEN CIRCUIT CHECK  table. If both resistance measurements are less than 5 ohms, replace compuvalve. If either resistance measurement is 5 ohms or more, repair affected circuit between FTT sensor and compuvalve. See WIRING DIAGRAMS article.
   COMPUVALVE TO FTT SENSOR OPEN CIRCUIT CHECK
   
   

   Compuvalve Harness Connector Terminal No. (Wire Color)	FTT Sensor Harness Connector Terminal No. (Wire Color)
   8 (White) (1)	1 (Black)
   26 (White) (1)	2 (Orange)
   (1) Wire colors from compuvalve are all White, except ground circuits which are Black. For compuvalve terminal locations, see Figure.

7. 7) Check FTT Circuits For Short To Ground
   
   Turn ignition switch to OFF position. Ensure FTT sensor is disconnected. Disconnect compuvalve harness connector C4025. Measure resistance between chassis ground and compuvalve harness connector C4025 terminals No. 8 (White wire) and 26 (White wire). See Figure. If resistance is 10 k/ohms or more, replace compuvalve. If resistance is less than 10 k/ohms, repair short to ground in affected circuit. See WIRING DIAGRAMS article.