P273F

Code

Generic P — Powertrain

Transmission Fluid Temperature Sensor B Over Temperature Condition

Brand: Generic

Type: P — Powertrain

Views: UK: 48 EN: 62 RU: 37

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Page language: EN

Causes

Actual transmission fluid overheating (internal or external cooling issue)
Failed or drifted transmission fluid temperature sensor (Sensor B)
Open, short, or high resistance in the sensor signal/ground wiring
Poor connector contact or corrosion at the sensor harness
Incorrect or contaminated transmission fluid (low level, wrong fluid)
Thermostat/cooler or radiator issue reducing cooling efficiency

Symptoms

Transmission may go into limp/ failsafe mode (reduced performance)
Transmission slipping, harsh shifts, or unusual shift timing
Illuminated MIL/Check Engine Light and/or Transmission warning lamp
Possible high transmission fluid temperature gauge reading (if equipped)
Noises from transmission if overheating is severe

What to check

Read and record freeze frame and live data — confirm sensor B temperature and compare to sensor A and coolant temps
Inspect sensor B connector and wiring for damage, corrosion, bent pins, or poor sealing
Check transmission fluid level, color, smell (burnt odor), and condition
Verify transmission cooler lines, cooler, and radiator cooling system are functioning
Backprobe sensor signal and ground with a multimeter or scope while warming vehicle
Measure sensor resistance at ambient and while heated/cooled and compare to manufacturer spec

Signal parameters

Sensor type: typically a thermistor (NTC or PTC) producing a variable resistance; some systems provide a 0–5 V signal to PCM
Expected signal range: 0–5 V depending on temperature and design (refer to vehicle specification for exact values)
Typical behavior: NTC resistance decreases as temperature rises (PTC increases); check manufacturer chart
Fault indications: open circuit → very high resistance or voltage at extreme end; short to ground → near 0 V; short to 5 V → near 5 V
Over-temperature threshold: varies by application (many systems flag fault above roughly 120–150 °C) — consult vehicle spec

Diagnostic algorithm

Retrieve freeze frame, I/M readiness, and all stored codes. Note conditions when fault set (load, temperature, vehicle speed).
Visually inspect sensor B harness and connector for damage, corrosion, or loose pins. Repair as needed.
With ignition ON (engine off) backprobe the sensor signal and ground. Verify wiring has reference voltage or proper circuit behavior per service data.
Start engine and monitor live data for sensor B temperature vs sensor A and engine coolant temp. Look for unrealistic jumps or constant extreme values.
Measure sensor resistance at ambient and while applying heat (hot water) or cold (ice) and verify resistance changes correctly. Compare to specification if available.
Check for shorts: disconnect sensor and measure continuity to power and ground to confirm no unintended shorts.
Inspect transmission fluid level/condition and cooling system (cooler, lines, radiator). Repair leaks, replace fluid if contaminated, and correct level.
If wiring and fluid/cooling check OK but sensor readings remain out of range, replace sensor B and retest.
After repairs clear codes, perform a test drive under similar conditions and monitor for return of P273F and any related codes.
If fault persists after sensor replacement and wiring verified, consider PCM/TCM diagnostic or replacement per manufacturer procedures.

Likely causes

Wiring or connector fault (open, short to voltage/ground, corrosion)
Failed/shorted temperature sensor B (thermistor failure)
Low transmission fluid level or degraded fluid causing overheating
Transmission cooler restriction or external cooling failure

Fault status

⚠️ Status

Transmission Fluid Temperature Sensor B Over Temperature Condition — PCM/TCM detected sensor B reporting temperature above allowable limit or a circuit condition consistent with over‑temperature. Inspect sensor, wiring, fluid level/condition, and cooling system.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-4.0 hours