P0183 Code: Fuel Temperature Sensor A Circuit High

What the P0183 code means

Fuel changes density with temperature: a gallon of cold fuel holds more mass than a gallon of hot fuel. Because the computer meters fuel by how long the injector stays open and not by mass, it needs to know that temperature to correct the calculation.

The fuel temperature sensor is a negative temperature coefficient thermistor, just like the coolant temperature sensor. Its resistance drops as the fuel heats up, and the computer works out the temperature from the voltage that is left.

The P0183 code is stored when that voltage stays above the upper limit. It does not match any real temperature. It means an open circuit, and the computer is reading its own reference voltage.

Its effects are milder than those of other sensor codes. The engine keeps running because the system falls back on a default value, but it loses some precision in metering. That shows up as slightly higher fuel consumption and, on a diesel, finer control of rail pressure is lost.

It helps to put into perspective how much this correction really matters. Diesel density changes by about one percent for every 10 °C (18 °F), so between fuel at 0 °C (32 °F) and fuel at 60 °C (140 °F) there is a noticeable difference in mass for a system that meters to the millisecond. It is not a decisive correction like fuel pressure or airflow, but it explains why, without it, you see a bit more fuel use and, on a diesel, slightly higher particulate emissions.

It is worth knowing where to look for the sensor, because its location varies more than most. It can be in the fuel return line, built into the fuel filter, inside the fuel pump module in the tank, or even on the rail itself. That spread explains why the repair bill swings so much: on some vehicles it is an easy $30 part, and on others you have to drop the whole pump module.

P0183 code symptoms

• Check engine light on.
• Slight increase in fuel consumption.
• Somewhat uneven idle on some vehicles.
• Slightly darker smoke when accelerating on diesel engines.
• The engine runs normally in most cases.
• Absurd fuel temperature reading on the scan tool.
• Cold starts that take a little longer.
• A repair quote that varies a lot depending on where the sensor is built in.

Likely causes of the P0183 code

1. Unplugged or poorly seated connector.
2. Signal wire cut or making a poor contact.
3. Sensor failed internally with an open circuit.
4. Corroded or backed-out connector pins.
5. Open sensor ground or one with high resistance.
6. Moisture in the connector, because it sits close to the fuel filter.
7. Wiring damaged by rubbing.
8. Wrong replacement sensor, with a different resistance curve.

How to diagnose the P0183 code step by step

1. Read the temperature in live data with the engine cold. It should be close to ambient. An absurdly low value confirms the open circuit.
2. Jumper the two connector pins with the key on. If the reading jumps to a very high temperature, the wiring is good and the sensor is the part that failed.
3. Measure the sensor resistance when cold and compare it with the specification.
4. Check the reference voltage at the signal pin with the sensor unplugged.
5. Verify ground continuity all the way to the computer.
6. Inspect the connector for moisture, green corrosion and backed-out pins.
7. Wiggle the harness with the key on while you watch the reading.
8. Locate the sensor before you quote the job. It can be in the return line, in the filter, in the pump module or on the rail, and the cost changes completely.

How to fix the P0183 code

• Plug the sensor back in if it was loose, and clean the pins with contact cleaner.
• Replace the sensor when the jumper test confirms the wiring is correct.
• Repair the damaged section of wire with solder and heat shrink.
• Clean or replace the corroded connector and protect it with dielectric grease.
• Fix the sensor ground by cleaning it down to bare metal.
• Use a sensor with the exact part number for the vehicle. The resistance curves are not interchangeable.
• Before you decide on the repair, check whether the sensor is sold separately or built into the filter or the pump module.

Technical reference data

• It is a negative temperature coefficient thermistor: resistance drops as the temperature rises.
• Typical resistance at 20 °C (68 °F): between 2 and 3 kilo-ohms.
• Typical resistance at 80 °C (176 °F): between 0.3 and 0.5 kilo-ohms.
• Voltage that sets the code: above 4.6 volts on a 5 volt reference.
• P0182 is the opposite code: low voltage, which is the same as absurdly hot fuel.
• The location varies: fuel return line, filter, pump module or rail, depending on the vehicle.

Brand-specific notes

This is one of the least serious codes in the fuel system. The engine runs, there is no mechanical risk, and the real effect is a loss of precision in fuel metering. That does not mean you should ignore it, but it does mean you can deal with it without urgency.

Before you order the part, unplug the sensor and plug it back in firmly. A connector that was not seated properly after a fuel filter change explains a good share of cases,.

Frequently asked questions about P0183