Symptom
Transmission overheating warning
A dedicated warning that gearbox fluid temperature is too high, often with power or gear selection restricted at the same time. Genuine overheating is serious — heat is what destroys automatic transmission fluid, and the damage accumulates rather than resetting when things cool down. But it can equally be caused by a temperature sensor circuit shorted to ground, which reads as impossibly hot, so a warning after gentle, brief driving deserves suspicion of the reading before the gearbox.
Also described as: transmission hot, gearbox overheating, trans temp warning, transmission temperature warning, gearbox too hot, trans overheat, transmission overheating, transmission too hot, هشدار داغ شدن گیربکس, گیربکس داغ کرد, caja cambios caliente, aviso transmision sobrecalentada, temperatura caja alta, حرارة الجير عالية, تحذير سخونة ناقل الحركة, الجير سخن
Some causes mean you should stop driving
3 of the 10 codes that produce this symptom indicate a fault where continuing to drive risks damage or is unsafe. If the symptom is sudden or severe, treat it as one of those until a scan says otherwise.
What this usually means
Genuine overheating is serious, and the reason is that the damage accumulates rather than resetting when things cool down. Heat is what destroys automatic transmission fluid: it oxidises, loses its friction modifiers, and the clutches it serves begin to slip — which makes more heat. A transmission that has been hot repeatedly is a transmission with a shortened life, even if it works perfectly today.
But a warning after gentle, brief driving deserves suspicion of the reading before the gearbox. A temperature sensor circuit shorted to ground reads as impossibly hot, and the module acts on it exactly as it would on a real reading — restricting gear selection or power. So the first question is whether the reported temperature is plausible for what the car has just been doing.
When it is genuine, the causes divide into making too much heat and removing too little. Making too much: slipping elements, a torque converter clutch that is not locking so slip is never removed, or towing and heavy loads beyond what the cooler was sized for. Removing too little: a blocked or bypassed cooler, air blocked in front of the radiator, or low fluid so there is less of it to carry heat away.
Limp mode is itself a heat source, which is the trap. A transmission that has locked into one gear usually leaves the torque converter unlocked, so a long journey in limp mode generates exactly the heat this warning is about — and the two faults then feed each other.
Working through it
| What you find | Likely cause | How to confirm it | What fixes it |
|---|---|---|---|
| Warning after a short, gentle journey | The reading rather than the temperature — a sensor circuit shorted to ground reads impossibly hot | Compare the reported temperature against what the car has been doing, and against ambient after standing overnight. Implausibility is the finding. | Repair the sensor or its circuit. Do not service the transmission on a reading that cannot be true. |
| Warning while towing or climbing under load | More heat than the cooler was sized to remove | Correlate with load and gradient. Check the cooler is clear and, on a towing vehicle, whether an auxiliary cooler was ever fitted. | Clear or upgrade the cooling, and service the fluid — it has been heat-cycled hard. |
| Warning alongside slipping or a flare | Slipping elements generating the heat — the overheating is a symptom of the slip | Read for slip and flare alongside temperature. Inspect fluid for burnt smell and material. | Repair the slipping element. Cooling work alone treats the symptom. |
| Warning appeared while driving in limp mode | The unlocked torque converter — limp mode generates the heat the warning is about | Establish which came first. Limp mode plus a long journey explains the temperature without a cooling fault. | Repair the original limp-mode fault and stop driving it in that state. The two faults compound. |
| Cooler lines or the cooler itself blocked, or the radiator packed with debris | Removing too little heat rather than making too much | Check flow through the cooler lines and inspect the front of the radiator stack, which collects leaves and insects. | Flush or renew the cooler, clean the stack. Service the fluid afterwards. |
| Fluid low | Less fluid to carry heat away, and a pump closer to drawing air — both raise temperature | Check by the manufacturer's procedure at the specified temperature. | Find the leak and correct the level. Topping up without finding it repeats the warning. |
-
Warning after a short, gentle journey
- Likely cause
- The reading rather than the temperature — a sensor circuit shorted to ground reads impossibly hot
- How to confirm it
- Compare the reported temperature against what the car has been doing, and against ambient after standing overnight. Implausibility is the finding.
- What fixes it
- Repair the sensor or its circuit. Do not service the transmission on a reading that cannot be true.
-
Warning while towing or climbing under load
- Likely cause
- More heat than the cooler was sized to remove
- How to confirm it
- Correlate with load and gradient. Check the cooler is clear and, on a towing vehicle, whether an auxiliary cooler was ever fitted.
- What fixes it
- Clear or upgrade the cooling, and service the fluid — it has been heat-cycled hard.
-
Warning alongside slipping or a flare
- Likely cause
- Slipping elements generating the heat — the overheating is a symptom of the slip
- How to confirm it
- Read for slip and flare alongside temperature. Inspect fluid for burnt smell and material.
- What fixes it
- Repair the slipping element. Cooling work alone treats the symptom.
-
Warning appeared while driving in limp mode
- Likely cause
- The unlocked torque converter — limp mode generates the heat the warning is about
- How to confirm it
- Establish which came first. Limp mode plus a long journey explains the temperature without a cooling fault.
- What fixes it
- Repair the original limp-mode fault and stop driving it in that state. The two faults compound.
-
Cooler lines or the cooler itself blocked, or the radiator packed with debris
- Likely cause
- Removing too little heat rather than making too much
- How to confirm it
- Check flow through the cooler lines and inspect the front of the radiator stack, which collects leaves and insects.
- What fixes it
- Flush or renew the cooler, clean the stack. Service the fluid afterwards.
-
Fluid low
- Likely cause
- Less fluid to carry heat away, and a pump closer to drawing air — both raise temperature
- How to confirm it
- Check by the manufacturer's procedure at the specified temperature.
- What fixes it
- Find the leak and correct the level. Topping up without finding it repeats the warning.
Codes that produce this symptom (10)
Listed with the codes that most typically present this way first — the likeliest place to start.
- P0712 Transmission Fluid Temperature Sensor A Circuit Low Typical of this code Moderate
- P0740 Torque Converter Clutch Circuit/Open Moderate
- P0741 Torque Converter Clutch Circuit Performance/Stuck Off Moderate
- P079A Transmission Friction Element A Slip Detected High
- P079B Transmission Friction Element B Slip Detected High
- P07A7 Transmission Friction Element C Stuck On Stop driving High
- P0868 Transmission Fluid Pressure Low Stop driving High
- P0894 Transmission Component Slipping Stop driving High
- P0939 Hydraulic Oil Temperature Sensor Circuit Low Moderate
- P0C1B Electric/Auxiliary Transmission Fluid Pump Control Module Internal Temperature Too High High
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
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