Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSFORD1994RANGER 2WD L4-140 2.3L SOHCREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSTESTING AND INSPECTIONPINPOINT TESTSTE - TRANSMISSION FLUID TEMPERATURE (TFT) SENSORTE10 - ATTEMPT TO GENERATE DTC 66 OR 638
1994 Ford Ranger 2WD L4-140 2.3L SOHC
TE10 - Attempt To Generate DTC 66 or 638
1994 Ford Ranger 2WD L4-140 2.3L SOHCSECTION TE10 - Attempt To Generate DTC 66 or 638
Diagnostic Trouble Code (DTC) 56 and 637 indicate the Transmission Fluid Temperature (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. Quick Test Appendix (Detailed Testing Instructions)
- 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 -- Remove jumper wire.
Refer to Transmission and Drivetrain for TFT sensor service.
No -- Remove jumper wire. Go to TE11.
RENDER: 1.0x
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.