P0425: Catalyst Temperature Sensor (Bank 1, Sensor 1)
General electrical fault detected in the catalyst temperature sensor on bank 1 sensor position 1. The ECU uses this signal to manage heater control and protect the catalyst from overtemperature.
What P0425 means
P0425 is a generic OBD-II powertrain code in the emissions group. Bank 1 is the side of the engine with cylinder 1 (inline engines only have bank 1).
- Check engine light
- Usually on
- Emissions-related
- Yes — can fail inspection
- Limp mode possible
- Not typical
- Drive cycle to clear
- Not required
Get it fixed
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Symptoms
- Check engine light on
- Failed emissions inspection
- Possibly slightly increased fuel consumption
- Sulfur (rotten egg) smell from exhaust under load
Common causes
- 01Cat temperature sensor failedMost likely
- 02Wiring or connector faultPossible
Can I drive with P0425?
Usually yes, for a short time.
The car will often drive normally, but get it diagnosed soon. Left alone it can raise fuel use and emissions and will fail an OBD inspection. If you notice rough running, warning lights flashing, overheating or a burning smell, stop driving.
Why we rate it moderate
- Turns on the check engine light
- Emissions-related: will usually fail an OBD inspection
Severity is our rule-based rating from the code’s flags in OBDex and the system it affects, not an inspection of your car. If the check engine light is flashing, or you notice overheating, low oil pressure, or brake or steering problems, stop driving and get help.
How to diagnose P0425
- 1
Confirm the code and save freeze-frame data
Read the codes with an OBD-II scan tool and note every code, not just P0425. Save the freeze-frame data (speed, load, temperature when the fault set) before clearing anything; it tells you when the fault happens.
- 2
Fix other faults first
If other codes are stored, start with power-supply, sensor-circuit and communication codes. They can cause this code as a side effect.
- 3
Compare upstream and downstream O2 sensors
With the engine warm, the upstream sensor should switch rapidly while the downstream one stays fairly steady. A downstream signal that mirrors the upstream one points to a worn catalyst; check for exhaust leaks and misfires first.
- 4
Test the likely causes in order
Start with the most likely cause and work down: Cat temperature sensor failed; wiring or connector fault. Test before replacing parts.
- 5
Check for recalls and service bulletins
Look up recalls for your exact vehicle with its VIN, and ask a dealer about technical service bulletins (TSBs). Manufacturers sometimes issue software updates or extended warranties for known faults.
- 6
Clear the code and verify the repair
After the repair, clear the code and drive the car under the conditions in the freeze-frame data to confirm it does not return.
P0425 repair cost estimate
Estimate, not a quote. Labor times are typical ranges for this code from OBDex, and $125/hr is an assumed rate. Shop rates and labor times vary by vehicle and region. Diagnosis time may be billed separately.
- DIY difficulty
- Moderate
- Good DIY job?
- Yes, with a scan tool
Needs a scan tool and some experience with testing.
Parts and systems involved
- Cat temperature sensor
- Sensor wiring
P0425 FAQ
What does P0425 mean?
P0425 means “Catalyst Temperature Sensor (Bank 1, Sensor 1)”. General electrical fault detected in the catalyst temperature sensor on bank 1 sensor position 1. The ECU uses this signal to manage heater control and protect the catalyst from overtemperature.
Is P0425 serious? Can I keep driving?
We rate P0425 as moderate severity. Usually yes, for a short time. The car will often drive normally, but get it diagnosed soon. Left alone it can raise fuel use and emissions and will fail an OBD inspection. If you notice rough running, warning lights flashing, overheating or a burning smell, stop driving.
What causes P0425?
The most common causes, from most to least likely: Cat temperature sensor failed; Wiring or connector fault. Test before replacing parts, because several causes can set the same code.
How much does it cost to fix P0425?
Typical labor is about $40–$250 at an assumed $125/hour shop rate, plus parts. That is an estimate, not a quote: labor times and rates vary by vehicle and region, and diagnosis may be billed separately.
Can I fix P0425 myself?
DIY difficulty is moderate. Many owners can handle it with a scan tool, a multimeter and basic hand tools. Always confirm the cause before buying parts.
Will P0425 clear itself?
If the fault was intermittent, the warning may go off once the computer stops seeing it, but the code stays in memory. Fix the cause; clearing the code alone doesn’t repair anything.