P0168
Temperature Too HighP0168 is a generic OBD-II powertrain diagnostic trouble code: Temperature Too High. It is logged by the engine control unit when the o2/lambda monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0168 means
P0168 is set when the powertrain control module (PCM) detects that fuel temperature has exceeded a manufacturer-defined threshold for a sustained period. The fuel temperature sensor — often integrated into the fuel composition sensor assembly — communicates via a square-wave frequency signal, where higher frequencies correspond to higher fuel temperatures. The PCM uses this reading to adjust fuel delivery strategy: injection pulse width, timing, and enrichment corrections all depend on knowing how hot the fuel is. Excessively high fuel temperature reduces fuel density, lowers its energy content per unit volume, and can degrade injector spray patterns, leading to lean combustion events. On flex-fuel platforms the risk is compounded because the PCM must simultaneously compensate for ethanol content. Many calibrations respond to a confirmed over-temperature condition with a power-derate (limp) strategy to protect injectors and prevent pre-ignition. Prolonged operation with overheated fuel can also accelerate injector coking and fuel-line degradation, so prompt diagnosis is warranted even when driveability symptoms appear mild.
Common causes
Most-frequently reported root causes when P0168 is logged.
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1
Defective or drifted fuel temperature / fuel composition sensor reporting falsely high values
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2
Damaged, corroded, shorted, or open wiring and connectors in the sensor circuit
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3
Excessively contaminated, low-grade, or wrong-grade fuel raising actual fuel temperature
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4
Cooling system fault (e.g. failed thermostat, low coolant) causing excessive underhood heat soak to the fuel rail
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5
Restricted or partially blocked fuel return line trapping hot fuel near the injectors
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6
Failed PCM or ECM (rare; only after all other causes are eliminated)
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7
Extended idling or low-speed driving in high ambient temperatures with inadequate fuel circulation
Symptoms drivers notice
How to diagnose P0168
A typical diagnostic flow when this code is present.
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1
Connect a scan tool, record all stored DTCs and freeze-frame data, and note the fuel temperature value at the time the code set
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2
Inspect fuel quality — if the code appeared shortly after refuelling, drain and replace with fresh high-quality fuel before further electrical diagnosis
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3
Perform a thorough visual inspection of sensor wiring, connectors, and harness routing for chafing, corrosion, or heat damage; repair any faults found and retest
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4
With KOEO (key-on engine-off), back-probe the sensor signal wire and verify reference voltage (typically 5 V) and a clean ground; compare live sensor reading on the scan tool against an infrared thermometer pointed at the fuel rail
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5
Check cooling system operation: verify coolant level, thermostat function, and that the engine reaches normal operating temperature without overshooting — excessive engine heat can raise fuel rail temperature
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6
Inspect the fuel return line for kinks, blockages, or a stuck pressure regulator that could trap hot fuel; low fuel flow can cause heat soak at the sensor
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7
If wiring and cooling system are normal and sensor readings remain implausible, replace the fuel temperature / fuel composition sensor and clear codes; if the code returns immediately, proceed to PCM diagnosis
Related powertrain codes
- P0040 — Upstream Oxygen Sensors Swapped From Bank To Bank
- P0041 — Downstream Oxygen Sensors Swapped From Bank To Bank
- P0130 — O2 Sensor Circuit Malfunction (Bank 1 Sensor 1)
- P0131 — O2 Sensor Circuit Low Voltage (Bank 1 Sensor I)
- P0132 — O2 Sensor Circuit High Voltage (Bank 1 Sensor 1)
- P0133 — O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)
Frequently asked questions
Can filling up with bad or contaminated fuel trigger P0168?
Yes. Low-quality or contaminated fuel has different thermal properties and can cause the sensor to report temperatures outside the expected range. Draining and refilling with fresh branded fuel is a recommended first step before electrical diagnosis.
Will P0168 put my car into limp mode?
It depends on the vehicle calibration. Many manufacturers program a power-derate or reduced-performance mode when fuel temperature exceeds a safe threshold to protect the injection system. If you notice reduced power alongside the MIL, assume limp mode is active and address the fault promptly.
Is P0168 the same as a fuel temperature sensor circuit code like P0180?
Not exactly. P0180–P0183 indicate a fault in the sensor circuit itself (out-of-range voltage). P0168 means the circuit is functioning but the temperature value reported is above the programmed limit — the sensor may be working correctly and fuel really is too hot, or the sensor is drifting high.
Can I keep driving with a P0168 code?
Short distances are generally possible, but the code should not be ignored. If the vehicle enters limp mode or exhibits rough running, stop driving and diagnose immediately. Sustained high fuel temperature can damage injectors and accelerate fuel system wear.
Disabling P0168 in software
RaceTune can permanently disable P0168 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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