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Transmission Fluid Temperature Sensor Circuit Malfunction

Jump to the fix

Severity

High

Can I keep driving?

Avoid extended driving; visit a service soon.

First step

A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training. 1. Read the codes and watch live transmission fluid temperature on a scan tool while the engine is cold, a sensor reading sat at minus 40C or an impossible high value tells you it's the circuit and not real heat 2.

  • PPowertrain
  • 0Generic code
  • 7Transmission
  • 10Sequence number

What does it mean?

The TFT (transmission fluid temperature) sensor is part of the automatic transmission fluid pressure (TFP) manual valve position switch and is a thermistor that changes value based on temperature. The TFT is an NTC (negative-temperature coefficient), which means that as the temperature increases, the resistance decreases, and as the temperature decreases, the resistance increases.

The PCM (powertrain control module) supplies a 5-volt reference signal to the sensor and measures the voltage drop in the circuit. When the transmission fluid is cold, the sensor resistance is high and the PCM detects high signal voltage. As the fluid temperature warms to a normal operating temperature, the resistance becomes less and the signal voltage decreases. This sensor is used by the PCM or TCM to detect the temperature of the automatic transmission fluid.

This signal is used to determine the best shift points and to regulate line pressure. It will cause the control module (PCM or TCM) to engage the TCC (torque converter clutch) sooner and disable overdrive, to help reduce the fluid temperature if it reaches higher than normal.

NOTE: Whenever diagnosing a 700 series DTC (Diagnostic Trouble Code) with a transmission, transfer case or other driveline components, check for a DTC under chassis and body systems, not just under “P” or powertrain/engine or emission control type codes. Module communications DTCs are “U” codes. These are most often found when looking for DTCs under chassis or body systems.

Chassis related codes are labeled “C” and body system related codes are labeled “B” codes and these can cause drivetrain issues if they affect a sensor that is also used by the heating and air conditioning system. Figure 1 TFT Circuit Wiring Diagram When the control module (PCM or TCM) detects one of the following unusual conditions, then DTC P0710 sets.

Unrealistically large change in transmission temperature Transmission temperature which remains constant for a period of time in which a measurable amount of change is expected and is a type C DTC

Symptoms

Likely causes

How to fix it

Codes From the Same System

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This information follows the generic OBD-II definition and does not replace a vehicle-specific diagnosis. The severity rating is rule-based; an authorised diagnostic reading is required for a definitive answer.