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Test B: Transmission Fluid Temperature Sensor

  1. Electronic Diagnostics

    Check transaxle harness connector. Inspect connector for damaged terminals, corrosion and loose wires. Ensure transaxle connector is fully seated. Repair as necessary. Go to next step.

  2. Check Electrical Signal Operation

    Ensure ignition switch is turned to OFF position. Disconnect transaxle harness connector. Measure voltage between transaxle harness connector terminal No. 5 and 9. See Figure . Turn ignition switch to ON position. If voltage is 4.75-5.25 volts, go to step  6 . If voltage is not within specification, go to next step.

  3. Check Continuity Of TFT Sensor Signal Return (SIG RTN) Circuits

    Turn ignition switch to OFF position. Disconnect PCM 104-pin connector, and inspect it for damaged terminals, corrosion and loose wires. Repair as necessary. Install breakout box, leaving PCM disconnected. Measure and record resistances between specified breakout box test pin and transaxle harness connector terminal. See TFT SENSOR HARNESS OPEN CIRCUIT TEST  table. If each resistance reading is less than 5 ohms, go to next step. If any resistance reading is 5 ohms or more, repair open circuit. Connect all components. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES  under DIAGNOSIS & TESTING. Repeat QUICK TEST  under DIAGNOSIS & TESTING.
    TFT SENSOR HARNESS OPEN CIRCUIT TEST

    Breakout Box TFT Sensor Circuit Test Pins No. Transaxle Connector Terminals No. (1)
    37 5
    91 9
    (1) See Figure .

  4. Check TFT Sensor Circuit For Short To VPWR & Ground

    Ensure ignition switch is turned to OFF position. Measure and record resistance between specified breakout box test pins. See TFT SENSOR SHORT CIRCUIT TEST  table. If any resistance reading is less than 10 k/ohms, repair short circuit. Connect all components. Disconnect breakout box. If each resistance reading is 10 k/ohms or more, go to next step.
    TFT SENSOR SHORT CIRCUIT TEST (1)

    Breakout Box TFT Sensor Test Pin No. Breakout Box Test Pins No.
    Continental
    37 71 & 97
    37 3, 25, 51, 77, 91 & 103
    37 Ground
    Sable & Taurus
    37 71
    37 24, 25, 51, 76, 77, 91 & 103
    37 Ground
    (1) Measure between breakout box test pins.
    5. NOTE: DTC P0712 is set if TFT sensor resistance falls below 597 ohms (short circuit). DTC P0713 is set if TFT sensor resistance exceeds 869 k/ohms (open circuit).

  5. Check Resistance Of TFT Sensor/Harness
    Ensure engine is at normal operating temperature. Install transmission tester. Set transmission tester Bench/Drive switch to BENCH position. Set gear select switch to OHMS CHECK. Measure and record resistance between TFT sensor jacks on transmission tester. Resistance should be within specification. See TFT SENSOR TEMPERATURE/RESISTANCE  table. If resistance reading is within specification for specific temperature, either warm up transaxle or allow transaxle to cool to check resistance at different temperatures. If resistances measured remain within specification, go to next step. If resistances measured are not within specification, go to step  7 .
    TFT SENSOR TEMPERATURE/RESISTANCE

    Temperature °F (°C) K/Ohms)
    -40 To -4 (-40 To -20) 284-967
    -3 To 31 (-19 To -1) 100-284
    32-68 (0-20) 37-100
    69-104 (21-40) 16-37
    105-158 (41-70) 5-16
    159-194 (71-90) 2.7-5
    195-230 (91-110) 1.5-2.7
    231-266 (111-130) .8-1.5
    267-302 (131-150) .5-.8

  6. Check TFT Sensor/Harness For Short To Ground

    Check continuity between BAT (-) jack and TFT sensor (-) and (+) jacks on transmission tester. If continuity exists, go to next step. If continuity does not exist, replace PCM. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES  under DIAGNOSIS & TESTING. Repeat QUICK TEST  under DIAGNOSIS & TESTING. If DTC is still present, go to next step.

  7. Internal Electronic Diagnostics

    Drain transaxle fluid. Remove transaxle side cover. Inspect internal harness connector at TFT sensor. Ensure all connectors are fully connected and not damaged. Repair as needed. Install all components in reverse order of disassembly. Fill transaxle with fluid. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES  under DIAGNOSIS & TESTING. Repeat QUICK TEST  under DIAGNOSIS & TESTING. If all connectors are okay, go to next step.

  8. Check Internal Harness Continuity

    Disconnect internal harness from TFT sensor. Connect positive lead of ohmmeter to transmission tester TFT (+) jack and negative lead to TFT sensor connector Black wire. Measure and record resistance. Connect positive lead of ohmmeter to transmission tester TFT (-) jack and negative lead to TFT sensor connector White wire. If both resistance readings are .5 ohm or less, go to next step. If either resistance reading is more than .5 ohm, replace internal harness. Go to step  10 .
    9. NOTE: Reading should be performed with a low current tester less than 200 milliamps.

  9. Check Internal Harness For Shorts To Ground
    Using transmission tester, check continuity between each TFT sensor connector terminal and BAT (-) terminal of transmission tester. If continuity does not exist in any circuit, go to next step. If continuity exists in any circuit, replace internal harness. Go to next step.

  10. Check TFT Sensor Resistance

    Using ohmmeter, check resistance between TFT sensor terminals. See TFT SENSOR TEMPERATURE/RESISTANCE  table. If resistance readings are within specification for specific temperature, go to next step. If resistance readings are not within specification, replace TFT sensor. Install all components in reverse order of disassembly. Fill transaxle with fluid. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES  under DIAGNOSIS & TESTING. Repeat QUICK TEST  under DIAGNOSIS & TESTING.

  11. Check TFT Sensor For Short To Ground

    Using ohmmeter, check continuity between each TFT sensor terminal and BAT (-) terminal of transmission tester. If continuity exists, replace TFT sensor. If continuity does not exist, install all components in reverse order of disassembly. Fill transaxle with fluid. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES  under DIAGNOSIS & TESTING. Repeat QUICK TEST  under DIAGNOSIS & TESTING. See SYMPTOM DIAGNOSIS under TROUBLE SHOOTING in FORD AX4N OVERHAUL article.
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