Pinpoint Test B - TFT Electrical Circuit

1) 4R44E & 4R55E Electronic Diagnostics Check transmission harness connector. Inspect connector for damaged pins, corrosion and loose wires. Ensure transmission connector is fully seated. Repair as necessary. Go to next step.
2) Check Electrical Signal Operation Ensure ignition is off. Disconnect transmission connector. Using DVOM, connect positive lead to transmission harness connector terminal No. 4 and negative lead to terminal No. 8. See Figure. Turn ignition on. If voltage is 4.75-5.25 volts, go to step 5). If voltage is not within specification, go to next step.
3) Check Continuity Of TFT Signal Return (SIG RTN) Circuits Turn ignition off. Disconnect PCM connector, and inspect it for damaged pins, corrosion and loose wires. Repair as necessary. Install breakout box, leaving PCM disconnected. On 1995 Explorer models, measure and record resistance between breakout box test pin No. 49 and transmission harness connector terminal No. 4. Measure and record resistance between test pin No. 46 and transmission harness connector terminal No. 8. On all other models, measure and record resistance between breakout box test pin No. 37 and transmission harness connector terminal No. 4. See Figure. Measure and record resistance between test pin No. 91 and transmission harness connector terminal No. 8. If each resistance is less than 5 ohms, go to next step. If any resistance is more than 5 ohms, repair open circuit. Connect all components. Disconnect breakout box. Erase all trouble codes. See CLEARING CODES. Repeat QUICK TEST.
4) Check TFT Circuit For Short To VPWR & Ground Ensure ignition is off. Disconnect PCM connector, and inspect it for damaged pins, corrosion and loose wires. Repair as necessary. Install breakout box, leaving PCM disconnected. On 1995 Explorer models, measure and record resistance between breakout box test pin No. 49 and test pins No. 37 and 57. On all other models, measure and record resistance between breakout box test pin No. 37 and test pins No. 71 and 97. If any resistance is less than 10 k/ohms, repair short circuit. Disconnect breakout box and repeat QUICK TEST. If resistance is 10 k/ohms or more, go to next step.
NOTE: DTC 637 or P0713 is set if resistance is above 869 k/ohms (open circuit). DTC 638 or P0712 is set if resistance is below 597 ohms (short circuit).

5) Check Resistance Of TFT Sensor Install transmission tester. Set tester Bench/Drive switch to BENCH position. Set Solenoid Selector switch to OHMS CHECK. Connect ohmmeter leads to appropriate TFT jacks. Measure and record resistance. Resistance should be within specification. See TFT TEMPERATURE/RESISTANCE TABLE . If resistance is within specification for specific temperature, either warm up transmission or allow transmission 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, replace internal harness. Erase all trouble codes. See CLEARING CODES. Repeat QUICK TEST.

TFT TEMPERATURE/RESISTANCE

Temperature °F (°C)	Resistance (k/Ohms)
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

6) Check TFT Sensor/Harness For Short To Ground Check continuity between BAT (-) tester jack and TFT jacks. If continuity exists, go to next step. If continuity does not exist, replace PCM. Erase all trouble codes. See CLEARING CODES. Repeat QUICK TEST.
7) Internal Electronic Diagnostics Drain transmission fluid. See TRANSMISSION SERVICING section. Remove transmission fluid pan. See VALVE BODY under ON-VEHICLE SERVICE in AUTO TRANS OVERHAUL - FORD 4R44E & 4R55E article. Inspect TFT internal wiring and harness connector. Ensure connector is fully connected and not damaged. Repair or replace as needed. Install all components in reverse order of disassembly. Fill transmission with fluid. Erase all trouble codes. See CLEARING CODES. Repeat QUICK TEST. If wiring and connectors are okay, replace internal harness.