P1299

Code

LAND ROVER P — Powertrain

Cylinder head protection failure

Brand: LAND ROVER

Type: P — Powertrain

Views: UK: 23 EN: 37 RU: 24

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Page language: EN

Causes

Faulty cylinder head temperature (CHT) or engine coolant temperature (ECT) sensor
Open, shorted or corroded wiring or poor connector to the sensor or ECM
Low coolant level, blocked coolant passages, or failed thermostat/water pump
Cooling fan failure or radiator blockage
Intermittent sensor signal or ECM software/hardware fault
Head gasket failure or internal coolant leak causing incorrect readings

Symptoms

Instrument cluster warning or specific cylinder head protection message
Check engine light illuminated and related DTC stored
Engine derate / limp-home mode or reduced power
Overheating indication on temperature gauge or sudden temperature spikes
Cooling fan running constantly or not running when expected
Possible coolant smell, visible leaks or white exhaust smoke (if head gasket)

What to check

Retrieve freeze frame and full DTC list with an OEM-capable scan tool; note related codes
Inspect coolant level and condition, radiator and reservoir for leaks
Visually inspect wiring and connectors to CHT/ECT sensor(s) and ECM for damage/corrosion
Monitor live sensor data (CHT/ECT) at idle and under load; compare to ambient
Confirm cooling fan operation, fan relays/fuses and thermostat function
Perform pressure test on cooling system and check for head gasket symptoms

Signal parameters

CHT/ECT sensor voltage typically varies ~0.3–4.5 V depending on temperature (sensor type dependent)
Resistance across thermistor sensor will change with temperature (refer to OEM spec tables)
Expected coolant temperature at warm idle: ~80–105 °C (manufacturer dependent)
No communication dropouts on CAN/diagnostic bus while monitoring

Diagnostic algorithm

Record all stored codes and freeze-frame data; note operating conditions when code set.
Visually inspect coolant level, hoses, radiator, fans, and look for leaks or contamination.
Using a scan tool, monitor cylinder head and coolant temperature sensors in real time while warming up and under mild load; watch for implausible or intermittent readings.
Backprobe the sensor connector. With ignition on, measure supply voltage and ground; verify signal voltage changes with temperature or when heating sensor with hot water (engine off) if safe.
Measure sensor resistance at ambient and compare to OEM chart; replace sensor if out of specification.
Inspect and continuity-test wiring from sensor to ECM; check for shorts to power/ground and for connectors damaged by heat near cylinder head.
Verify cooling fan operation, fan relay, fuses and thermostat operation; repair/replace as required.
Pressure-test cooling system and perform combustion leak (block) test if head gasket breach suspected.
If wiring/sensor/cooling system are good but fault persists, check for ECM software updates and consider ECM diagnosis/replacement per OEM procedures.
After repairs, clear codes and perform road test under conditions that previously caused the fault; confirm code does not return.

Likely causes

CHT/ECT sensor out of range or intermittent
Broken/chafed wiring harness near cylinder head (heat-damaged)
Coolant loss or airlock causing local overheating at head
Cooling fan not operating under load or relay/fuse fault
Failed thermostat stuck closed causing rapid head temperature rise

Fault status

⚠️ Status

Cylinder head protection failure detected. Possible overheating or sensor/circuit fault. Check coolant level, sensors, wiring, cooling fan and repair before further engine use to avoid damage.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1-4 hours

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P1299 — Cylinder head protection failure