OBD-II trouble code
P0549: Exhaust Gas Temperature Sensor Circuit High Bank 2 Sensor 1
Signal voltage above the ceiling on the second bank's exhaust temperature sensor. Whether this code appeared alone or alongside its bank 1 counterpart is the single most informative thing about it, because it decides how far upstream the fault has to be.
Quick facts
- System
- Powertrain
- Category
- Exhaust / Aftertreatment
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $130 – $1,200
- DIY difficulty
- Advanced DIY
What does P0549 mean?
Start with the arithmetic of what else is stored, because on this code the pattern is worth more than any single measurement.
If P0549 is stored on its own, the fault is confined to hardware that only bank 2 uses: that sensor, that branch of the harness, that connector. Two sensors do not fail open in the same week, so a solitary code keeps the search local. If P0549 and P0546 are both stored — the same fault on both banks at once — the honest reading is that the sensors are almost certainly fine and something they share has failed. The candidates for that are short and specific: a common ground, the reference supply that feeds both circuits, a shared junction where both branches meet the main harness, or the module connector itself. Replacing two sensors to chase a shared ground is a costly, avoidable mistake, and the code pattern tells you not to make it before you spend anything.
On the mechanism itself, a signal above the ceiling means the circuit has gone open far more often than it means the circuit found power. The module holds the line up at reference and depends on the sensor to pull it down; with the connection broken, nothing pulls and it floats to the top. That opens the list to severed things — a snapped conductor, a burned-out element, a connector that has walked out of its lock, a terminal that no longer grips.
Bank 2 has a specific mechanical reason for open circuits that bank 1 largely does not, and it is worth knowing before you go looking. On transverse V engines the rear bank sits close to the firewall, and the engine rocks toward and away from it on every torque reversal — pulling away from a stop, lifting off, shifting under load. A lead routed across that gap with too little slack is being stretched and released tens of thousands of times a year. Conductors fatigue and break at the anchor point, usually inside insulation that still looks perfect, so the break is invisible and the connector at the sensor tests fine. Look at where the branch is clamped rather than at either end of it.
The last thing worth naming is why this code has a poor reputation for being fixed correctly. An implausibly hot reading triggers a protective derate, so the driver arrives with one symptom: no power. Bank 2 is the hidden side of the engine, so the visual inspection that would find a cracked connector or a stretched lead gets skipped in favour of the part that can be ordered. The sensor gets replaced, the derate persists, and the actual break is still there in a harness nobody looked at. Do the jumper test before ordering anything.
Common causes
- Open conductor in the bank 2 branch, typically fatigued at a clamp point where the harness spans engine movement
- Connector unlatched, cracked or walked out of its lock on the less accessible side of the engine
- Failed sensor with an element that has gone open after long service
- Terminal that has lost tension and no longer grips the mating pin
- Corroded terminals adding enough resistance that the module reads the circuit as open
- Lost ground path on the bank 2 side, which the module cannot distinguish from a broken signal wire
- Harness stretched or trapped during a previous rear-bank spark plug, manifold or intake job
- Shared reference or ground failure, which is the likely cause when the bank 1 high code is stored at the same time
Symptoms
- Noticeable loss of power, often the only symptom the driver reports
- Check engine light with a reduced-power or wrench indicator on many applications
- Bank 2 exhaust temperature pinned at the top of its range including on a cold engine
- Boost lower than normal on twin-turbo applications where the module protects the bank 2 turbine
- No regeneration attempted at all, since the module believes the exhaust is already beyond target temperature
- Power that returns briefly and then disappears again, consistent with a marginal connection making and breaking
- Both bank 1 and bank 2 high codes stored together, pointing at a shared ground or reference rather than the sensors
- Fault triggered by hard acceleration or gear changes, when engine rock is greatest
Diagnostic steps
- 1.Read every stored code before touching anything and note whether the bank 1 high code is present too. Two symmetrical codes at once means the fault is in what the two circuits share — ground, reference or the module connector — and that changes where you start and saves the cost of two sensors.
- 2.Check the live bank 2 temperature with the engine cold. An extreme reading on a cold engine confirms the fault is electrical rather than a genuine overtemperature, which rules out chasing an exhaust restriction or a fuelling problem.
- 3.Jumper the two harness pins at the sensor connector and watch the value. Bridging the circuit removes the open, so the reading should swing hard to the opposite extreme. If it does, everything from the connector back to the module is healthy and the sensor or its terminals are the problem. If nothing moves, the break is upstream and the sensor is not worth ordering.
- 4.Flex the bank 2 branch by hand at every clamp and anchor point with live data displayed. A conductor fatigued inside intact insulation will show itself as the reading jumping when the harness is moved, and this finds breaks that no continuity test catches while the wire happens to be touching.
- 5.Inspect the section that spans engine movement with particular care. On transverse engines the rear bank branch has to bridge the gap between a rocking engine and a fixed body, and a lead routed with too little slack fatigues where it is anchored rather than in the middle of the free length.
- 6.Verify the sensor ground separately from the signal. A lost ground reads to the module exactly like a broken signal wire, and testing only the signal side leaves half the circuit unproven — which is how a replaced sensor ends up not fixing anything.
Repair cost
$130 – $1,200
A connector re-seated or a terminal repaired is $130 to $300. A wiring repair on the bank 2 branch typically runs $200 to $500, higher than the bank 1 equivalent because a good part of the branch is not visible until things are moved out of the way. Sensor replacement is $200 to $450 with reasonable access and up to $1,200 where the intake manifold has to come off to reach the rear bank. If the bank 1 high code is stored alongside this one, the likely repair is a shared ground or connector at $150 to $400 and not two sensors — checking the pattern first is worth several hundred dollars on its own.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with exhaust gas temperature (egt) sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an advanced DIY job. It typically requires specialty tools, scan-tool access, lifting equipment, or careful sequencing to avoid causing new failures. Plan for extended downtime and have a backup vehicle. Most owners are better served by a shop that has done this repair before.