P0549 Code Definition
The P0549 code is a generic powertrain code related to vehicle speed controls and idle control system problems. In this case, the engine control module (ECM) has found a fault with the exhaust gas temperature sensor circuit, receiving higher than normal voltage signals in bank 2 sensor 1.
Codes related to the P0549 include: * P0547: Exhaust Gas Temp. Sensor Circuit (Bank 2) * P0548: Exhaust Gas Temp. Sensor Circuit Low (Bank 2) * P2034: Exhaust Gas Temp. Sensor Circuit (Bank 2 Sensor 2) * P2035: Exhaust Gas Temp. Sensor Circuit Low (Bank 2 Sensor 2) * P2036: Exhaust Gas Temp. Sensor Circuit High (Bank 2 Sensor 2) * P2082: Exhaust Gas Temp. Sensor Circuit Range/Performance (Bank 2 Sensor 1) * P2083: Exhaust Gas Temp. Sensor Circuit Intermittent (Bank 2 Sensor 1) * P2086: Exhaust Gas Temp. Sensor Circuit Range/Performance (Bank 2 Sensor 2) * P2087: Exhaust Gas Temp. Sensor Circuit Intermittent (Bank 2 Sensor 2)
What the P0549 Code Means
A P0549 code is stored when the exhaust gas temperature sensor registers a high voltage from the bank 2 sensor on the exhaust gas temperature sensor (the side of the engine that does not contain Cylinder 1).
A vehicle’s exhaust gas temperature sensor is most commonly a two-wire sensor. It is a heat sensitive resistor, which converts exhaust temperature to a voltage signal read by the ECM. The sensor is located upstream from the catalytic converter. In a diesel engine, the exhaust gas temperature sensor is going to be most frequently located by the diesel particulate filter (DPF). The exhaust gas temperature sensor is solely responsible for protecting a catalytic converter from excessive heat damage.
The sensor is sent a 5-volt signal from the ECM from one wire, while the second wire is ground. If the signal is higher than 5-volts, a P0549 code is stored, signaling higher than normal exhaust gas temperatures.
What Causes the P0549 Code?
Several problems may cause a P0549 code including: * Damaged or defective exhaust gas temperature sensor * Open or shorted exhaust gas temperature sensor harness * Missing insulation that may cause a short directly to ground * Damaged, faulty, loose, or poor electrical connection to exhaust gas temperature sensor * Use of an aftermarket off-road exhaust system may cause a decrease in pressure * Exhaust leak upstream from exhaust temperature sensor * Damaged or defective ECM (rare)
What are the Symptoms of the P0549 Code?
Symptoms of a P0549 code may include: * Check engine or warning light may illuminate * There may be no symptoms other than a stored P0549 code
How Does a Mechanic Diagnose the P0549 Code?
A mechanic may use several methods to diagnose a P0549 trouble code, including: * Utilize an OBD-II scanner to check for a stored P0549 trouble code * Locate the exhaust gas temperature sensor, which will vary in location depending on whether the model is a gasoline or diesel (sensors in a gasoline model will be between the exhaust manifold and converter, sensors in a diesel model will be located before the DPF) * Locate the specific Bank (in this case, bank 2), which will be on the side of the engine that does not contain Cylinder 1 * Visually inspect the sensor and related circuitry for visible signs of damage, including missing insulation or bare wiring * Remove the exhaust gas temperature sensor and use a digital volt/ohmmeter to check resistance; approximate 150 ohms is the goal * Check voltage on engine side of the pigtail, if 5 volts is not found, the ECM may need to be replaced
Common Mistakes when Diagnosing the P0549 Code
The oxygen sensor may be incorrectly identified as the culprit of the P0549 code, when the true problem is the exhaust gas temperature sensor.
How Serious is the P0549 Code?
Because a vehicle’s safe driving operation most likely will not be impacted due to faults that store a P0549 code, this code is not considered a potentially serious code. When this code appears, it is recommended to take your vehicle to your local service center or mechanic for repair and diagnosis as soon as possible.
What Repairs can Fix the P0549 Code?
Several repairs can fix a P0549 trouble code and include: * Repair any damaged or shorted, open, or loose wiring or connectors * Replace the damaged or defective exhaust gas temperature sensor * Replace or repair the exhaust system, depending on whether aftermarket parts were used or parts may have been removed * Replace a damaged or defective ECM (rare) * Clear all codes, test-drive the vehicle, and rescan to see if any codes reappear
Additional Comments for Consideration Regarding the P0549 Code
This code is frequently found on vehicles with aftermarket exhaust systems, or a catback system. In addition, it is recommended to ensure that any aftermarket system utilized on your vehicle is fully compliant with state emissions laws and regulations.
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