Fuel Rail Pressure Sensor "A" Circuit High

What it means

The fuel rail pressure sensor signal voltage is above the normal range. The fuel rail pressure sensor measures fuel pressure in the fuel rail so the ECU can control the fuel pump and injector timing. A high signal is usually caused by an open circuit (unplugged, broken wire), a missing ground or a short to voltage.

Symptoms

• Check engine light on
• Hard starting or long cranking
• Hesitation and loss of power
• Stalling
• Engine in reduced power mode (common on diesels and direct injection)

Probable causes

Most likely first

1. 1Open sensor ground wire
2. 2Signal wire shorted to the 5V reference or to battery voltage
3. 3Corroded connector terminals
4. 4Failed sensor

How to diagnose it

Work through these in order before buying parts

1. 1Record the code and its freeze frame data (speed, load, temperature when it set), then clear it and see if it comes back.
2. 2Inspect the fuel rail pressure sensor connector and wiring (on the fuel rail feeding the injectors). Look for corrosion, bent or pushed-back pins, oil contamination and chafed insulation.
3. 3Watch the fuel rail pressure sensor reading on live data. Compare the reading with the specified pressure for your engine at idle and under load. A mechanical gauge confirms whether the sensor or the pressure is wrong.
4. 4With the key on and the sensor unplugged, check for about 5 volts on the reference wire and a good ground (under 0.1 V drop) on the ground wire. Back-probe the signal wire with the sensor connected and watch the voltage change smoothly.
5. 5If the wiring checks out, test the sensor itself against the specification in a service manual.
6. 6Check for technical service bulletins (TSBs) or software updates for your make and model; some codes have known factory fixes.

Common fixes

• Repair the damaged wiring or connector
• Replace the fuel rail pressure sensor
• Clear the code and test drive to confirm the repair