P0427 code meaning
Catalyst Temperature Sensor Circuit Low Bank 1 Sensor 1
Powertrain system Generic code P04xx codes Check engine light
What P0427 means
Some engines – mainly diesels – measure the temperature at or in the catalyst with a thermistor in a voltage divider instead of only modelling it; most makers report exhaust temperature sensors under P0544 ff, P2031 ff or P2080 ff instead. Sensor 1 of bank 1 is the first catalyst temperature sensor on the side with cylinder 1. P0427 means the signal voltage is below its lower limit – typically the signal wire is shorted to ground or the sensor is shorted internally. FCA's 3.0-litre EcoDiesel uses this sensor (middle of the oxidation catalyst and particulate filter unit), but no document available to us names this particular code.
P0427 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 1.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P0427
- Check engine light on
- Usually no noticeable change (substitute value from the model)
- Diesel: filter regeneration distorted or blocked, possibly further codes such as P2459 or P0420
Common causes of P0427
- Most likelySignal wire shorted to ground (chafed)
- PossibleSensor shorted internally
- PossibleWater or corrosion in the connector
- Less likelyEngine module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Catalyst temperature sensor b1s1Sensor wiringEngine control module
What each part of P0427 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| 27 | The exact fault in that area. |
What to do next
- Note P0427 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0427
What does P0427 mean?
P0427 means "Catalyst Temperature Sensor Circuit Low Bank 1 Sensor 1". Some engines – mainly diesels – measure the temperature at or in the catalyst with a thermistor in a voltage divider instead of only modelling it; most makers report exhaust temperature sensors under P0544 ff, P2031 ff or P2080 ff instead. It is a generic code, so it means the same on every make.
Is it safe to drive with P0427?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0427 fail an emissions test?
Yes, it can. P0427 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0427 to fix?
Difficulty: medium. A typical repair takes 0.5 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0427 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.