OBD-II trouble code
P2085: Exhaust Gas Temperature Sensor Circuit Intermittent Bank 1 Sensor 2
The only exhaust temperature sensor whose wiring lives outside the engine bay entirely. That changes the failure list from heat and vibration to water, salt and stone chips — and it makes this the cheapest fault in the family to actually look at.
Quick facts
- System
- Powertrain
- Category
- Exhaust / Aftertreatment
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $90 – $620
- DIY difficulty
- Intermediate DIY
Browse every code in P2000–P20E8, or start from the full code library.
What does P2085 mean?
P2085 means the second exhaust temperature sensor on bank 1 briefly produced a signal the module rejected, then returned to normal.
The useful starting point is that this sensor does not live where the others do. The upstream sensors are bolted into manifolds and turbine housings inside the engine bay, surrounded by shielding, above the airflow, in a hot dry environment. This one is downstream of the catalyst or the filter, which on most vehicles puts it under the floor, ahead of or beside the rear axle, with its harness clipped to the underbody rather than to the engine. That single difference rewrites the failure list.
Underfloor means wet. The section of exhaust past the aftertreatment device is the coolest part of the system, and on short journeys it may never reach a temperature that boils off the water condensing inside and outside it. The harness and connector there see spray, standing water, car-wash pressure and, in any region that salts its roads, a corrosive solution that wicks into connector bodies and sits in them. Corrosion of that kind rarely produces a clean open circuit. It produces a joint whose resistance changes with temperature and with movement, which is precisely the behaviour that sets an intermittent code and then clears itself. The fault that follows the weather, rather than the engine, is the signature of this position.
Underfloor also means exposed to impact. Nothing shields this harness from what the tyres throw at it. Stones, road debris, ice thrown off the wheel arches and the occasional kerb or speed bump all reach it, and on a lowered vehicle so does the ground. It is also routinely damaged by people rather than by the road: an underbody jacking point or a trolley jack pad placed carelessly crushes whatever is clipped nearby, and exhaust hangers that have perished let the whole system swing far enough to drag the lead against the floor pan. A fault that begins immediately after a tyre change, an exhaust replacement or a service is worth treating as a handling injury until proved otherwise.
The compensation for all of this is that P2085 is, in diagnostic terms, the cheapest of the exhaust temperature intermittents to investigate. Everything that can fail is visible. Put the vehicle on a lift with the exhaust cold, and the entire run from sensor to body connector can be inspected end to end in a few minutes, with the connector opened and the clips checked along the way. There is no engine cover to remove, no ducting in the way, no reaching blind behind a bulkhead. That means the correct order of work on this code is inverted compared with its bank 2 equivalent: look first, and measure only if looking found nothing.
One more practical point about proving a repair. Because the trigger here is often water rather than movement, a wiggle test on a dry vehicle can pass convincingly and tell you nothing. If the driver's occurrences follow rain, washes or winter mornings, reproduce that condition deliberately: a gentle low-pressure water spray directed at the connector and the suspect section, with the channel recorded live, will find a corroded joint that no amount of shaking would have revealed.
Common causes
- Corroded terminals in a connector that has stood full of water or road salt solution
- Connector seal perished or the locking latch not fully seated after previous underbody work
- Harness chafed against the floor pan or a heat shield by an exhaust hanging on perished rubbers
- Lead crushed by a trolley jack, lift arm or axle stand placed on or near a clipped section
- Stone or road debris strike cutting through insulation without severing the conductor
- Broken underbody clip letting the lead sag into contact with a moving or hot surface
- Ice building up in the wheel arch and loading the harness on winter journeys
- Green corrosion wicking up inside the cable under the insulation from an earlier water entry
- Sensor loose in its boss, so the assembly moves with a swinging exhaust rather than staying put
- Internal connection cracked inside the sensor body from repeated heat and quench cycles
Symptoms
- Warning light that comes on and clears itself, often days apart
- Occurrences clustering after rain, car washes or on salted winter roads
- Temperature trace dropping to zero or jumping to full scale for a fraction of a second
- Recorded minimum and maximum values at the extremes of the scale despite normal live readings
- Diesel regeneration cycles interrupted partway through and rescheduled
- Fault appearing soon after a tyre change, exhaust job or underbody service
- Nothing reproducible during a dry workshop test
- Visible green or white corrosion at the connector when it is finally opened
- Rattle or knock from the exhaust over bumps if a hanger has perished
- No matching circuit code stored, because no fault lasted long enough to set one
Diagnostic steps
- 1.Put the vehicle on a lift with the exhaust cold and inspect the whole run before measuring anything. This is the one exhaust temperature circuit you can see end to end in a few minutes, so looking is cheaper than testing here.
- 2.Open the connector and examine the terminals for corrosion, green wicking and a seal that has hardened or gone missing. A joint full of salt solution behaves exactly like an intermittent and passes every static test once it dries.
- 3.Ask what the weather was doing when it happened. Occurrences that follow rain, washes or winter mornings point at water ingress; occurrences on rough surfaces point at clips and chafe instead.
- 4.Reproduce the wet condition deliberately if the history suggests it. A gentle low-pressure spray onto the connector and the suspect section, with the channel recorded live, finds corroded joints that shaking never will.
- 5.Check the exhaust hangers and rubbers. A system that swings drags the lead against the floor pan and heat shields, and replacing the harness without replacing the hanger simply restarts the clock.
- 6.Follow the harness past every clip and look for a crushed section near a jacking point or lift pad. This damage is common, is caused by people rather than the road, and is usually obvious once you are looking for it.
- 7.Record the channel with a graphing tool or a min and max capture through a normal drive. A minimum at the bottom of the scale and a maximum at the top, on a sensor that reads sensibly in front of you, confirms dropouts nobody witnessed.
- 8.Flex the lead in short sections rather than shaking the whole loom, so a positive result actually localises the fault instead of merely proving one exists.
- 9.Confirm the sensor is properly torqued into its boss, because a loose assembly moves with the exhaust and multiplies whatever mechanical stress the lead is already under.
- 10.After repair, drive the vehicle in conditions matching the original complaint. A fault triggered by water is not proved fixed by a dry road test.
Repair cost
$90 – $620
Diagnosis is $100 to $200, at the low end for this family because the entire circuit can be inspected visually on a lift. Cleaning or replacing corroded connector terminals and resealing the joint is $70 to $210 and is the most common real outcome. Repairing a chafed or crushed section and restoring the clips is $90 to $280. Replacing perished exhaust hangers, when a swinging system is the underlying cause, is $60 to $220. The sensor itself is $60 to $300 in parts with 0.4 to 1.2 hours of labour, plus extra if it has seized into a boss that has spent years under a wet, salted floor.
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 intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.