Transmission Fluid Temperature (TFT) Sensor

1994 PCED OBDI-A

SECTION 6A: EEC-IV Pinpoint Test
Procedures

TE: Transmission Fluid Temperature (TFT) Sensor

TE1 DIAGNOSTIC TROUBLE CODES (DTCS) 26 OR 636: INCREASE/DECREASE TRANSMISSION FLUID TEMPERATURE

DTCs 26/636 indicate the output of the Transmission Fluid Temperature (TFT) sensor was out of Self-Test range. The sensor output shows a failure occurred at either the low or high end of the acceptable range. The correct range of measurement is from 0.76 to 4.69 volts for Escort/Tracer and from 0.21 to 3.50 volts for all others.

Possible causes:

Fluid levels not to specification.
Transmission fluid not at operating temperature.
Sensor resistance out of limits.
Damaged Powertrain Control Module (PCM).

Drive vehicle through normal city traffic to bring transmission oil temperature to at least 10°C (50°F).
Rerun Quick Test.

Is DTC 26 or 636 present?

Yes	No
GO to TE2.	TFT sensor OK. SERVICE other DTCs as necessary. RETURN to Quick Test to SERVICE other DTCs as necessary.

TE2 CHECK FOR VREF AT THROTTLE POSITION SENSOR

Key off.
Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.
Install breakout box and connect PCM to breakout box.
Disconnect TP sensor.
Key on, engine off.
Measure voltage between VREF and SIG RTN at the sensor vehicle harness connector. Refer to schematic in Pinpoint Test DH or DQ.

Is the voltage between 4.0 and 6.0 volts?

Yes	No
RECONNECT TP sensor. GO to TE3.	GO to Pinpoint Test Step C1.

TE3 CHECK TFT SENSOR RESISTANCE CHANGE AS TRANSMISSION FLUID TEMPERATURE VARIES

Key off.
Breakout box installed, PCM disconnected.
Key on, engine off.
Verify that transmission fluid pan is warm to the touch.
IF IT IS TOO HOT TO TOUCH:

Measure and record TFT sensor resistance between TFT test pin (refer to chart) and Test Pin 46 at breakout box, then let transmission cool down and repeat measurement. The last resistance measurement should be greater than the first.

IF IT IS COLD:

Measure and record the TFT sensor resistance between TFT test pin (refer to chart) and Test Pin 46 at the breakout box, then reconnect PCM and drive vehicle for short time to elevate oil temperature. Disconnect PCM and repeat the measurements at the breakout box. The last resistance should be less than the first.

Did resistance measurement differ and was last measurement within specifications? (Refer to applicable chart at the beginning of this Pinpoint Test for the resistance specifications).

Transmission Type	CD4E 4R70W AODE AX4S E4OD (5.0L SFI)	E4OD (except 5.0L SFI and 7.3L diesel)	E4OD (7.3L diesel)	4EAT
TFT TEST PIN	49	42	7	2

Yes	No
REPLACE PCM. REMOVE breakout box. RERUN Quick Test.	REMOVE breakout box. RECONNECT PCM. For Escort/Tracer: GO to TE25. For all others: REFER to Transmission Group in the Service Manual for TFT sensor service.

TE10 DIAGNOSTIC TROUBLE CODES (DTCS) 56 OR 637: ATTEMPT TO GENERATE DTC 66 OR 638

DTCs 56 and 637 indicate the TFT sensor output is greater than Self-Test maximum value of 4.8 volts.

Possible causes:

Fluid levels not to specification.
Damaged TFT sensor.
Open harness circuit(s).
Damaged Powertrain Control Module (PCM).

Key off.
Disconnect transmission connector at TFT sensor. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.
Insert a jumper wire from the TFT circuit to SIG RTN circuit at transmission vehicle harness connector.
Run Key On Engine Off Self-Test.

Is DTC 66 or 638 present?

Note: Disregard any other DTC generated at this time. If no DTCs are generated (module not responding), go to TE12.

Yes	No
REMOVE jumper wire. For Escort/Tracer: GO to TE25. For all others: REFER to Transmission Group in the Service Manual for TFT sensor service.	REMOVE jumper wire. GO to TE11.

TE11 CHECK CONTINUITY OF TFT AND SIG RTN CIRCUITS

Key off.
Transmission connector disconnected.
Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.
Install breakout box, leave PCM disconnected.
Measure resistance between TFT circuit at transmission vehicle harness connector and TFT test pin (refer to chart) at breakout box.
Measure resistance between SIG RTN circuit at transmission vehicle harness connector and Test Pin 46 at the breakout box.

Are both resistances less than 5.0 ohms?

Transmission Type	CD4E 4R70W AODE AX4S E4OD (5.0L SFI)	E4OD (except 5.0L SFI and 7.3L diesel)	E4OD (7.3L diesel)	4EAT
TFT TEST PIN	49	42	7	2

Yes	No
GO to TE12.	SERVICE open circuit(s). REMOVE breakout box. RECONNECT all components. RERUN Quick Test.

TE12 CHECK TFT CIRCUIT FOR SHORT TO VPWR

Key off.
Transmission connector disconnected.
Breakout box installed, PCM disconnected.
Measure resistance between TFT Test Pin (refer to chart in TE11) and Test Pins 37/57 at breakout box.

Is each resistance greater than 10,000 ohms?

Yes	No
REPLACE PCM. REMOVE breakout box. RECONNECT all components. RERUN Quick Test.	SERVICE short circuit(s). REMOVE breakout box. RECONNECT all components. RERUN Quick Test.

TE20 DIAGNOSTIC TROUBLE CODES (DTCS) 66 OR 638: ATTEMPT TO GENERATE DTCS 56 OR 637

DTCs 66 and 638 indicate that TFT sensor output was less than the allowed Self-Test minimum value of 0.57 volts for Escort/Tracer and 0.15 volts for all others.

Possible causes:

Fluid levels not to specification.
Damaged TFT sensor.
TFT shorted to ground.
Damaged Powertrain Control Module (PCM).

Key off.
Disconnect transmission connector. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.
Run Key On Engine Off (KOEO) Self-Test (transmission connector remains disconnected for KOEO Self-Test).

Is DTC 56 or 637 present?

Note: Disregard any other DTC generated at this time.

Yes	No
For Escort/Tracer: GO to TE25. For all others: REFER to Transmission Group in the Service Manual for TFT sensor service.	GO to TE21.

TE21 CHECK VREF AT THE THROTTLE POSITION SENSOR

Key off.
Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.
Install breakout box and connect PCM to breakout box.
Disconnect TP sensor.
Key on, engine off.
Measure voltage between VREF and SIG RTN circuits at TP sensor vehicle harness connector. Refer to schematic in Pinpoint Test DH or DQ.

Is voltage between 4.0 and 6.0 volts?

Yes	No
RECONNECT TP sensor. GO to TE22.	GO to Pinpoint Test Step C1.

TE22 CHECK TFT CIRCUIT FOR SHORT TO GROUND

Key off.
Transmission connector disconnected.
Breakout box installed, disconnect PCM.
Measure resistance between TFT test pin (refer to chart) and Test Pins 40, 60 and 46 at the breakout box.

Is each resistance greater than 10,000 ohms?

Transmission Type	CD4E 4R70W AODE AX4S E4OD (5.0L SFI)	E4OD (except 5.0L SFI and 7.3L diesel)	E4OD (7.3L diesel)	4EAT
TFT TEST PIN	49	42	7	2

Yes	No
REPLACE PCM. REMOVE breakout box. RECONNECT all components. RERUN Quick Test.	SERVICE short circuit. REMOVE breakout box. RECONNECT all components. RERUN Quick Test.

TE25 CHECK TRANSMISSION WIRING

Key off.
Check transmission connector/external wiring for opens or shorts. Service as necessary.
Check internal transmission wiring for opens or shorts. Refer to Transmission Group in the Service Manual for disassembly procedures.

Is transmission wiring OK?

Yes	No
REPLACE TFT sensor. REASSEMBLE/ RECONNECT all components. RERUN Quick Test.	SERVICE as necessary. REASSEMBLE/ RECONNECT all components. RERUN Quick Test.

TE90 DIAGNOSTIC TROUBLE CODES (DTCS) 637/638: CHECK HARNESS AND CONNECTORS FOR INTERMITTENT OPENS OR SHORTS

Continuous Memory DTCs 637 or 638 indicate that sometime during the last 80 warm-up cycles, a fault has been detected in Transmission Fluid Temperature circuit.

Possible causes:

Fluid levels not to specification.
Intermittent open/short in harness.
Intermittent fault in TFT sensor.

Key off.
Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.
Install breakout box and reconnect PCM.
Connect DVOM between Test Pin 2 and Test Pin 46 at breakout box.
DVOM on 20 volts scale.
Key on, engine off.
Note TFT sensor voltage.
Perform the following while observing DVOM for a TFT/SIG RTN fault indication (voltage should remain stable or change gradually. A short to ground will be indicated by a reading of zero volts, an open by a reading of five volts and a short to power by a reading of greater than five volts):

Shake, wiggle and bend TFT and SIG RTN wires between transmission and PCM.

Is a fault indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. REMOVE breakout box. RECONNECT all components. RE-EVALUATE symptom.	For further diagnosis using the EEC-IV monitor box or Scan Tool, REFER to Section 7A. If an EEC-IV monitor box or Scan Tool is not available, GO to Pinpoint Test Step TD22 to check the TFT circuits).

TE100 DIAGNOSTIC TROUBLE CODES (DTCS) 68/657: RERUN KEY ON ENGINE OFF SELF-TEST

DTCs 68/657 indicate a transmission over temperature condition occurred.

Possible causes:

Damaged transmission cooling system.
Excessive loading, e.g. trailer towing.
Damaged clutch.
Improper transmission fluid level.
Damaged transmission connector.
Damaged TFT sensor circuit.

Key off.
Disconnect transmission connector. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary and reconnect.
Run Key On Engine Off Self-Test, record all DTCs.

Any transmission related DTC generated?

Note: If DTCs 68/657 repeat and no other DTC is generated, refer to Transmission Group in Service Manual for transmission over temperature condition.

Yes	No
ADDRESS any transmission related DTC by referring to the DTC charts in Dianostic Routines, Section 2A.	REFER to Transmission Group in Service Manual for over temperature condition (check clutch transmission fluid level etc.).