Description
Fuel Temperature Sensor for Citroën and Peugeot vehicles with 2.0 HDi RHY engines with Siemens fuel injection.
Overview
This fuel temperature sensor (part number 1579AY) monitors the temperature of diesel fuel and supplies that signal to the engine control unit. Accurate fuel temperature information helps the ECU adapt injection timing and quantity, improve cold-start behavior, optimize combustion and support emission control strategies on 2.0 HDi RHY engines equipped with Siemens injection systems.
Why This Part Matters
The ECU uses fuel temperature data to compensate fuel metering and injection timing. A faulty fuel temperature sensor can cause poor starting, increased fuel consumption, unstable idle or longer DPF regeneration cycles. Replacing a damaged sensor restores reliable engine management and helps maintain fuel economy and emissions performance.
Compatibility
Commonly fitted to Citroën and Peugeot applications with the 2.0 HDi RHY engine and Siemens injection. Typical vehicle models where this sensor is used include:
Installation
Replacement is straightforward for a trained technician. General steps:
- Depressurize the fuel system according to the workshop manual before disconnecting fittings.
- Disconnect the electrical connector and remove any retaining clips.
- Unscrew the sensor from its seat using the correct socket or wrench; retain or replace sealing ring/O‑ring.
- Fit the new sensor with a new seal and tighten to the manufacturer’s torque specification.
- Prime the fuel system and carry out bleed/priming procedure to remove air (follow vehicle-specific instructions for HDi systems).
- Check for leaks and clear any stored fault codes; verify correct operation with a diagnostic tool if available.
Installation Recommendations
Use a new sealing washer or O‑ring when installing the replacement sensor. Keep the connector and wiring clean and free of corrosion. Avoid overtightening—always respect the manufacturer’s torque specification. Work in a well-ventilated area and follow standard safety precautions for handling diesel fuel. If air enters the high-pressure diesel system, perform priming and bleeding exactly as specified for the HDi system to prevent damage to the high-pressure pump and injectors.
Common Failure Causes
- Fuel Contamination: Particles, water or degraded fuel can contaminate the sensor and cause incorrect readings.
- Connector Corrosion: Moisture in the connector leads to poor electrical contact or intermittent signals.
- Mechanical Damage: Impact or improper removal can damage the sensor body or thread/seal.
- Thermal Aging: Long-term exposure to heat and vibration may degrade the sensing element.
Technical Information
- Manufacturer: Stellantis / Citroën Peugeot
- Model: Vehicles with 2.0 HDi RHY engine (Siemens Injection)
- Product Codes: 1579AY
- Other Numbers: NFP
Practical Notes For Mechanics
When diagnosing, corroborate temperature readings with live data from a diagnostic tool where available. Replace the sensor if data is erratic or contradicts expected values. After installation, verify system operation by checking for absence of fuel-related fault codes and confirming stable engine behavior during cold start and normal running.
Part Number 1579AY. Order now to restore accurate fuel temperature measurement and ensure correct ECU fuel management on affected Citroën and Peugeot HDi/RHY applications.
