P2740

Code

Generic P — Powertrain

Transmission Fluid Temperature Sensor B Circuit

Brand: Generic

Type: P — Powertrain

Views: UK: 27 EN: 115 RU: 27

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Page language: EN

Causes

Open or short in TFT sensor B wiring (to power, signal, or ground)
Corroded, loose or damaged connector/pin at sensor or control module
Failed transmission fluid temperature sensor B (internal fault)
Short to 5V reference or to chassis ground
Fluid contamination or internal sensor damage
Faulty PCM/TCM (rare) or poor module ground/power

Symptoms

Check Engine Light / MIL illuminated
Stored P2740 and possibly related transmission codes
Incorrect transmission temperature reading in live data or erratic values
Transmission may enter limp mode or exhibit abnormal shifting (in some vehicles)
Possible failed readiness for emissions monitors

What to check

Retrieve freeze frame and full code list; note related codes and readiness status
Scan tool: monitor transmission fluid temperature B live data and compare to sensor A (if present)
Visually inspect sensor connector, wiring harness, and nearby components for damage or fluid contamination
Backprobe connector and measure sensor voltage with ignition on and engine off/running as required
Check for continuity and shorts to ground or battery voltage between harness pins and module
Wiggle harness and connector while observing live data or watching for code set to identify intermittent faults

Signal parameters

Typical sensor is a thermistor type: signal varies with temperature (resistance changes as fluid temp changes)
Expected signal voltage range: approximately 0.1–4.9 V (varies by vehicle) — low voltage at one extreme, high at the other
Open-circuit condition often reads near battery/ignition reference (~4.5–5V) or scanner shows 'open'
Short-to-ground condition often reads near 0–0.2 V
Sensor response should change smoothly with temperature (no jumpy or frozen values); response time depending on sensor design

Diagnostic algorithm

Connect an OBD-II scanner and confirm P2740 and any related codes; record freeze frame/live data for TFT Sensor B.
Visually inspect transmission area for fluid leaks, damaged wiring, corroded connectors, or harness chafing.
With ignition ON (engine off unless manufacturer requires running), backprobe the TFT B connector and measure signal voltage vs. ground. Compare to expected range. Note open or short conditions.
Measure sensor resistance (if service info provides values) by disconnecting connector and checking across sensor terminals; verify resistance changes with temperature (warm/cold).
Check continuity from sensor signal pin to the PCM/TCM pin; check for short to battery voltage or chassis ground. Repair any harness faults found.
If wiring and connector are good but signal is incorrect, replace the TFT sensor B and retest.
If a new sensor still shows incorrect readings and wiring is verified, inspect PCM/TCM power and ground circuits and consider module fault (consult manufacturer procedures before replacement).
After repair, clear codes, perform a road or heater-soak test to confirm proper sensor response and that P2740 does not return.

Likely causes

Damaged wiring harness near transmission (chafing, heat, or rodent damage)
Connector corrosion from fluid leak or moisture intrusion
Sensor failure after high mileage or fluid contamination
Poor ground at transmission or module
Intermittent fault caused by vibration or loose terminal

Fault status

⚠️ Status

P2740 - Transmission Fluid Temperature Sensor B Circuit: signal out-of-range (open, short to ground/5V, intermittent) detected by PCM/TCM. Check sensor, wiring, connector, and module circuits.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours