Tranny coolant temp sensor??

[Hermyclaus]

As soon as the outside temp. drops below 50 deg F. The torque converter will not lock up untill about 15 miles of driving. Less if it is around town, not highway. When it's the middle of winter (30 deg or lower) the converter never locks up on the highway. Pulled codes and got an ECT out of range. Replaced ECT and thermostat and still have problem. Is there a tranny coolant temp sensor somewhere? The converter works fine in the summer. Only when it gets cold outside does it screw up.
Thanks, Chris

 

[Rob94]

I don't know much about automatic transmissions. I do know that if the engine was not at normal operating temperature when you pulled the codes, you may have gotten an erroneous ECT sensor code.

 

[Slo-Sho]

http://www.autosafety.org/article.php?scid=100&did=564

 

[Rockledge]

Article No. 96-7-13

TORQUE CONVERTER - AX4S - NO TORQUE CONVERTER CLUTCH ENGAGEMENT IN COLD WEATHER - 3.2L SHO MODELS

Publication Date: MARCH 25, 1996

FORD: 1993-95 TAURUS

This TSB is being republished in its entirety to include 1995 model year vehicles.

ISSUE:
Some customers may experience overdrive not engaging which is related to no torque converter clutch engagement in cold weather.

ACTION:
Inform the customer that the condition is normal. Refer to the following statement for specific details.

The torque converter clutch is designed not to engage until the transaxle has reached normal operating temperature. This is due to the higher efficiency transaxle cooler used for the 3.2L applications.

If the vehicle has been parked for some time in cold weather, it may require several miles of driving to warm the transaxle.

If the vehicle had been previously driven and restarted while still warm, engagement of the torque converter clutch will occur much sooner.

Both conditions are normal and are intended to optimize both cold and warm weather driveability and fuel economy.

Torque converter clutch engagement may occur anywhere between 19°C (66°F) (3.095 volts) and 49°C (120°F) (1.710 volts) Transmission Oil Temperature (TOT) providing Engine Coolant Temperature (ECT) is greater than 54°C (130°F) (1.513 volts).

OTHER APPLICABLE ARTICLES:
NONE

SUPERSEDES:
94-12-12

WARRANTY STATUS:
INFORMATION ONLY

 

[Hermyclaus]

Rockledge:
Thanks, But this problem just started last year. Prior to that it would be normal to drive the car 5 miles or so before converter engagement. ( wintertime) Now it's all the way to work 22 miles at 40 deg. and no engagement. Is it possible that the TOT sensor is malfunctioning and not throwing a code? And if so ,where is it located?

 

[Rockledge]

Sounds like a logical possibility. Here is what my Ford Manual says about the TOT:

Transmission Oil Temperature (TOT) Sensor

The transmission oil temperature sensor (TOT sensor) (7H141) is located on the transmission main control valve body. It is a temperature-sensitive device called a thermistor. The resistance value of the TOT will vary with transmission fluid temperature change. The powertrain control module monitors the voltage across the TOT to determine the temperature of the transmission fluid.Transmission Function: The powertrain control module uses this signal to determine whether a cold start shift schedule is necessary. The cold start shift schedule allows quicker shifts when the transmission fluid is cold. The PCM also inhibits torque converter clutch operation at low transmission fluid temperatures. Corrects EPC pressures for temperature.

Symptoms: Torque converter clutch engagement and stabilized shift schedules happen too soon after a cold start. Harsh or soft shifts.

 

[Hermyclaus]

OK sounds good so far.
If I can locate the 2 wires coming from the trans wiring harness that are the 2 leads from the TOT sensor, I could check the resistance across them after the engine and tranny are warm but, still not engaging the converter. That would confirm it as being the problem. The range looks to be 3.095 or lower. if it's above 3.1volts,then it's the problem. If it falls in the operating voltage range, then I'm not sure where to go next.

I'ts due for another tranny fluid change soon. So I might just replace the TOT at that time, Depending on cost.
Thanks, Chris