P0549
Exhaust Gas Temperature Sensor Circuit High Bank 2 Sensor 1.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 5
- AreaVehicle speed, idle control and auxiliary inputs
- 49
- FaultThe specific fault in that area
What it means
P0549 is the generic code for a high input fault in the exhaust gas temperature (EGT) sensor circuit on Bank 2, Sensor 1, which is normally the sensor closest to the engine on the bank without cylinder number one. The control unit saw a signal voltage above the expected range, usually from an open circuit, a short to voltage or a failed sensor. With no trustworthy temperature reading, the unit may limit engine output or stop managing the exhaust aftertreatment properly.
Symptoms
- Engine warning light on
- Reduced power or limp mode
- Diesel particulate filter warning or failed regeneration
- Poor fuel economy
- Turbo protection strategy active, with limited boost on some models
- Other EGT or aftertreatment codes stored alongside
Possible causes
- Open circuit or high resistance in the sensor wiring or connector, such as corrosion, a pushed-out pin or a broken wirelikely
- Failed Bank 2 Sensor 1 exhaust gas temperature sensorlikely
- Wiring chafed or heat-damaged near the exhaust, shorting to a voltage supplypossible
- Damaged reference voltage supply or ground shared with other sensorspossible
- Fault inside the engine control unit or a related control modulerare
- Outdated control unit software that mis-reads the sensor, only where the manufacturer has documented thisrare
How to diagnose
- Read all stored and pending codes and note any other EGT, DPF or sensor supply faults, then review the freeze frame data.
- Check the live EGT reading for Bank 2 Sensor 1 and compare it with the other EGT sensors on a cold engine; they should be close to ambient and similar.
- Inspect the sensor, wiring and connector for heat damage, chafing, corrosion, water ingress and bent or loose pins.
- Unplug the sensor and check what the live reading does; a reading that stays at the maximum suggests a wiring or control unit side fault, while a change points to the sensor.
- With the ignition on, check the reference voltage and ground at the sensor connector against the manufacturer's data.
- Test the signal wire for continuity to the control unit and for a short to voltage, with the connectors disconnected.
- Measure the sensor resistance at a known temperature against the manufacturer's specification, as the correct values depend on the model and sensor type.
- Check for software updates or technical bulletins for your model before considering the control unit.
How to fix
- Repair or replace damaged wiring, and clean or replace corroded connector terminals.
- Replace the Bank 2 Sensor 1 exhaust gas temperature sensor if it is out of specification, using the correct part for the engine.
- Secure and re-route the loom away from heat and sharp edges after repairing it.
- Restore the reference voltage or ground supply if it is faulty.
- Update the control unit software only where a documented update covers this fault.
- Clear the code after repair and confirm it stays away on a road test, including a regeneration cycle where relevant.
Can I keep driving?
The car can usually be driven for a short time, but the control unit may limit power and the exhaust aftertreatment may not be protected. Get it checked soon, as running without a working temperature sensor can lead to a blocked particulate filter or heat damage.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.