P0183 on the LB7 Duramax is a fuel temperature sensor A circuit high input fault. The LB7 monitors fuel temperature so the ECM can correct injection quantity and timing as fuel density changes with heat. When the ECM reads a fuel temperature voltage too high, corresponding to an implausibly cold reading, it stores P0183.
Fuel temperature compensation helps the LB7 deliver consistent power and economy across a range of conditions, from a cold winter start to hot fuel returning from the injectors on a summer tow. A skewed reading throws off that correction, so while P0183 rarely strands a truck, it is worth fixing to keep fueling accurate. As a thermistor circuit, it almost always comes down to wiring, the connector, or the sensor.
What P0183 means
The fuel temperature sensor is a thermistor whose resistance rises as fuel cools. High resistance produces high signal voltage, which the ECM reads as very cold fuel. P0183 sets when the voltage stays at the high end, pointing to an open circuit, a disconnected sensor, or a sensor that has failed open.
Common causes
- Open signal or ground wire in the sensor circuit
- Disconnected or corroded sensor connector
- Failed fuel temperature sensor reading open
- Chafed harness that has broken a conductor
- Water or corrosion in the connector
Symptoms
- Check engine light with P0183 stored
- Minor fueling or economy changes
- Fuel temperature reading pinned very cold
- Usually little noticeable drivability change
- Companion fuel temperature codes such as P0182
How to diagnose it
Watch fuel temperature data with a scan tool. A reading pinned at an extreme cold value, well below ambient, confirms the high circuit fault. Inspect the sensor connector for corrosion and a secure fit. Back-probe the circuit: shorting the signal to ground briefly should drive the reading to the opposite extreme if the wiring is intact, which separates an open wire from an open sensor. Check the signal and ground wires for opens back to the ECM, and measure the sensor resistance against a temperature chart.
How to fix it
Repair an open signal or ground wire and clean or reconnect a corroded connector, which fixes many P0183 cases. If the wiring checks good but the sensor reads open, replace the fuel temperature sensor. Confirm the connector is sealed against moisture. After the repair, clear the code, verify the fuel temperature reading matches ambient after a cold soak, and road test. For the correct fuel temperature sensor for your LB7 Duramax, contact sales@coredieselparts.com.
Frequently asked questions
What is the difference between P0182 and P0183?
P0182 is the fuel temperature circuit reading too low and P0183 is the same circuit reading too high. Both point at the fuel temperature sensor wiring, from opposite electrical directions.
Is P0183 safe to drive with?
Short term, yes. Drivability is usually only slightly affected, but the fueling correction is off, so repair it promptly to restore accurate performance and economy.
Can cold weather trigger P0183?
Genuine cold does not set the code, but an open circuit reads as impossibly cold. If the code appears in mild weather, the wiring or sensor is at fault, not the temperature.
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