Symptom
Fault only appears once the engine is hot
The car is perfect cold and misbehaves after twenty minutes, on a long run, or in traffic on a hot day. Heat is the classic exposer of a marginal connection, because metal expands: a joint that is just about making contact cold can open as it warms, and a semiconductor that is just about working can stop. It is also how a component that is slowly failing announces itself, since most are specified to work at temperature and fail their tolerance there first. Whether it comes back after cooling is the question to answer — one that does is thermal, one that does not has broken.
Also described as: only when hot, after twenty minutes, once its warmed up, worse when hot, happens on long journeys, only in traffic on hot days, فقط وقتی داغ میشود, بعد از گرم شدن موتور, solo falla en caliente, pasa cuando se calienta, solo con motor caliente, falla cuando se calienta, فقط بعد ما تسخن, المشكلة على الساخن, تظهر لما يحمى المحرك
Some causes mean you should stop driving
29 of the 142 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
Heat is the classic exposer of a marginal connection, because metal expands. A joint that is just about making contact cold can open as it warms, and a semiconductor that is just about working can stop. It is also how a component that is slowly failing announces itself, since most are specified to work at temperature and fail their tolerance there first.
The question to answer is whether it comes back after cooling. One that does is thermal — a connection or a device whose behaviour follows temperature. One that does not has broken, and the heat merely finished it.
Distinguish engine heat from ambient heat, because they implicate different places. A fault that appears after twenty minutes of running regardless of weather points at something close to the engine or exhaust — a sensor, a connector on the block, a harness section that gets radiated heat. A fault that only appears on hot days, or in traffic, points at underbonnet air temperature rather than at a specific hot component — and at anything cooled by airflow, which stops when the car does.
Reproduce it rather than waiting for it. A heat gun on a low setting, about 15 cm from one suspect area at a time while the signal is monitored, brings on in minutes what a road test takes an hour to find. The discipline is one area at a time, because heating a whole engine bay tells you nothing about where.
The crankshaft position sensor deserves naming. It is the archetypal heat-dependent failure on a petrol engine — perfect cold, absent hot, and it stops the engine outright rather than degrading — and it is checked in seconds by watching live engine speed during a hot crank.
Working through it
| What you find | Likely cause | How to confirm it | What fixes it |
|---|---|---|---|
| Appears after roughly twenty minutes of running, any weather | Something close to the engine or exhaust — a sensor, a connector, or a heated harness section | Heat gun on low, about 15 cm, on one suspect area at a time while monitoring the affected signal. One area at a time is the discipline. | Repair the joint or renew the component the test names. Do not diagnose this cold; a cold test passes. |
| Only on hot days or in slow traffic | Underbonnet air temperature, or something that depends on airflow which stops when the car does | Reproduce in traffic or with the vehicle stationary at temperature. Check cooling fans actually run when they should. | Repair the cooling or heat-shielding shortfall, or renew the heat-sensitive component. |
| Comes back to normal after the car stands and cools | Genuinely thermal — a connection or device whose behaviour follows temperature rather than having failed | Recovery on cooling is the discriminator. Log the fault against a temperature reading rather than against time. | Repair the connection or renew the device. Thermal faults get worse, not better. |
| Did not recover after cooling | It has broken rather than being thermal — the heat finished a component that was already going | Test normally now that the fault is permanent, which is much easier than chasing an intermittent. | Diagnose and repair conventionally. The heat pattern was the history, not the current state. |
| Engine cuts out when hot and will not restart until it cools | A heat-dependent crank position sensor, ignition module, or a fuel pump drawing more current warm | Watch live engine speed during a hot crank: an engine that plainly turns while reporting zero rpm is the sensor. | Renew what the hot test condemns. Inspect the reluctor and connector before fitting a sensor. |
| Appears at a repeatable point every time | A temperature threshold in the control strategy rather than a failing part — closed loop, a fan stage, or a protection limit | Log coolant, intake and where possible component temperatures against the moment it happens. A threshold shows as a step. | Diagnose what the threshold triggers. Repeatability at one temperature is a strategy, not a marginal joint. |
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Appears after roughly twenty minutes of running, any weather
- Likely cause
- Something close to the engine or exhaust — a sensor, a connector, or a heated harness section
- How to confirm it
- Heat gun on low, about 15 cm, on one suspect area at a time while monitoring the affected signal. One area at a time is the discipline.
- What fixes it
- Repair the joint or renew the component the test names. Do not diagnose this cold; a cold test passes.
-
Only on hot days or in slow traffic
- Likely cause
- Underbonnet air temperature, or something that depends on airflow which stops when the car does
- How to confirm it
- Reproduce in traffic or with the vehicle stationary at temperature. Check cooling fans actually run when they should.
- What fixes it
- Repair the cooling or heat-shielding shortfall, or renew the heat-sensitive component.
-
Comes back to normal after the car stands and cools
- Likely cause
- Genuinely thermal — a connection or device whose behaviour follows temperature rather than having failed
- How to confirm it
- Recovery on cooling is the discriminator. Log the fault against a temperature reading rather than against time.
- What fixes it
- Repair the connection or renew the device. Thermal faults get worse, not better.
-
Did not recover after cooling
- Likely cause
- It has broken rather than being thermal — the heat finished a component that was already going
- How to confirm it
- Test normally now that the fault is permanent, which is much easier than chasing an intermittent.
- What fixes it
- Diagnose and repair conventionally. The heat pattern was the history, not the current state.
-
Engine cuts out when hot and will not restart until it cools
- Likely cause
- A heat-dependent crank position sensor, ignition module, or a fuel pump drawing more current warm
- How to confirm it
- Watch live engine speed during a hot crank: an engine that plainly turns while reporting zero rpm is the sensor.
- What fixes it
- Renew what the hot test condemns. Inspect the reluctor and connector before fitting a sensor.
-
Appears at a repeatable point every time
- Likely cause
- A temperature threshold in the control strategy rather than a failing part — closed loop, a fan stage, or a protection limit
- How to confirm it
- Log coolant, intake and where possible component temperatures against the moment it happens. A threshold shows as a step.
- What fixes it
- Diagnose what the threshold triggers. Repeatability at one temperature is a strategy, not a marginal joint.
Codes that produce this symptom (142)
Listed with the codes that most typically present this way first — the likeliest place to start.
- C0072 Brake Temperature Too High Typical of this code High
- P0030 O2 Sensor Heater Control Circuit — Bank 1 Sensor 1 Typical of this code Moderate
- P0071 Ambient Air Temperature Sensor Circuit A Range/Performance Typical of this code Low
- P00B2 Radiator Coolant Temperature Sensor Circuit Range/Performance Typical of this code Moderate
- P00C6 Fuel Rail Pressure Too Low - Engine Cranking Bank 1 Typical of this code High
- P0127 Intake Air Temperature Too High Typical of this code Moderate
- P032F Combustion Engine Producing Insufficient Torque Typical of this code High
- P0350 Ignition Coil Primary/Secondary Circuit/Open Typical of this code Stop driving High
- P0426 Catalyst Temperature Sensor Circuit Range/Performance Bank 1 Sensor 1 Typical of this code Low
- P0441 Evaporative Emission System Incorrect Purge Flow Typical of this code Low
- P0526 Fan Speed Sensor Circuit Typical of this code Moderate
- P0528 Fan Speed Sensor Circuit No Signal Typical of this code Moderate
- P0554 Power Steering Pressure Sensor/Switch Circuit Intermittent Typical of this code Low
- P0786 Shift Timing Solenoid A Range/Performance Typical of this code High
- P079B Transmission Friction Element B Slip Detected Typical of this code High
- P0D70 Air Conditioning Compressor Control Module Internal Temperature Sensor A Circuit Typical of this code Moderate
- P0D71 Air Conditioning Compressor Control Module Internal Temperature Sensor A Performance Typical of this code Moderate
- P0D72 Air Conditioning Compressor Control Module Internal Temperature Sensor A Circuit High Typical of this code Moderate
- P0D73 Air Conditioning Compressor Control Module Internal Temperature Sensor A Circuit Low Typical of this code Moderate
- P0D74 Air Conditioning Compressor Control Module Internal Temperature Sensor A Circuit Intermittent/Erratic Typical of this code Moderate
- P0D75 Air Conditioning Compressor Control Module Output Driver Temperature Sensor Circuit Typical of this code Moderate
- P0D76 Air Conditioning Compressor Control Module Output Driver Temperature Sensor Performance Typical of this code Moderate
- P0D77 Air Conditioning Compressor Control Module Output Driver Temperature Sensor Circuit High Typical of this code Moderate
- P0D78 Air Conditioning Compressor Control Module Output Driver Temperature Sensor Circuit Low Typical of this code Moderate
- P0D79 Air Conditioning Compressor Control Module Output Driver Temperature Sensor Circuit Intermittent/Erratic Typical of this code Moderate
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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