Pinpoint Test B: Transmission Fluid Temperature (TFT) Sensor

WARNING: This page is about a different car, the 2009 Mercury Grand Marquis and 2009 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Refer to the Transmission Internal Harness Connector illustration in Transmission Connector Layouts .

B1 ELECTRONIC DIAGNOSTICS
WARNING: If equipped with fire suppression system, depower the system. For important safety warnings and procedures, refer to FIRE SUPPRESSION SYSTEM article.
- Vehicle in PARK.
- Key in OFF position.
- Check to make sure the transmission harness connector is fully seated, pins are fully engaged in connector and in good condition before proceeding.
- Connect the diagnostic tool.
- Key in ON position.
- Access the transmission PIDs.
- Is the scan tool able to access the transmission PIDs?
1. YES : Go to B2.
2. NO : REPEAT procedure to access the transmission PIDs. If the scan tool did not access the transmission PIDs, REFER to the INTRODUCTION - GASOLINE ENGINES article for diagnosis of PCM. If equipped with a fire suppression system, go to B5.
B2 WARM-UP/COOL-DOWN CYCLE
- While monitoring the TFT PIDs, carry out the following test: If transmission is cold, run transmission to warm it up. If transmission is warm, allow transmission to cool down.
- Do the TFT PIDs increase as the transmission is warmed up or decrease as the transmission is cooled, or does the TFT or TFT voltage drop in and out of range?
1. YES : If the TFT PIDs increase as the transmission is warmed or decrease as the transmission is cooled, CLEAR all DTCs. ROAD TEST to verify if concern is still present. If concern is still present, REFER to Diagnosis By Symptom in this article to diagnose transmission overheating.
  If the TFT or TFT voltage drop in and out of range, INSPECT for intermittent concern in the internal/external harness, sensor or connector. If equipped with a fire suppression system, go to B5.
2. NO : Go to B3.
B3 ELECTRICAL SIGNAL CHECK
- Key in ON position.
- Remove transmission fluid pan.
- Visually inspect the lead frame and connectors for damage.
- Measure the voltage with the positive lead to positive TFT at sensor pin and negative lead to a good ground.
- Is any voltage present?
1. YES : Go to B4.
2. NO : CHECK for open or short circuit in vehicle harness, internal harness or a PCM concern. If equipped with a fire suppression system, go to B5.

B4 CHECK THE RESISTANCE OF THE TFT SENSOR

Disconnect: Transmission Harness

Fig 2: Measuring Resistance

Courtesy of FORD MOTOR CO.

Measure the resistance between the positive TFT and negative TFT pins at transmission connector, using the following:

TRANSMISSION FLUID TEMPERATURE (TFT)

°C	°F	Resistance (Ohms)
-40 to -20	-40 to -4	967K-284K
-19 to -1	-3 to 31	284K-100K
0-20	32-68	100K-37K
21-40	69-104	37K-16K
41-70	105-158	16K-5K
71-90	159-194	5K-2.7K
91-110	195-230	2.7K-1.5K
111-130	231-266	1.5K-0.8K
131-150	267-302	0.8K-0.54K

Is the resistance correct?

YES : REFER to Diagnosis By Symptom in this article to diagnose an overheating concern. If equipped with a fire suppression system, go to B5.
NO : INSTALL a new internal harness (sensor is part of harness). If equipped with a fire suppression system, go to B5.

B5 REPOWER THE FIRE SUPPRESSION SYSTEM
WARNING: If equipped with fire suppression system, repower the system. For important safety warnings and procedures, refer to FIRE SUPPRESSION SYSTEM article.
- Verify that the fire suppression system is repowered. Refer to FIRE SUPPRESSION SYSTEM article.
- Is the fire suppression system repowered?
1. YES : Fire suppression system repowering is complete.
2. NO : REFER to FIRE SUPPRESSION SYSTEM article for fire suppression system depowering and repowering procedure.