OBD-II code · Powertrain (generic)
P0427 Catalyst Temperature Sensor Circuit Low (Bank 1 Sensor 1)
Catalyst temperature sensor at bank 1 sensor 1 below lower plausibility — short to ground. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
Is it safe to drive with P0427?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyShort to ground
- Less likelyConnector pins corroded - high contact resistance
- Less likelyHarness chafing through insulation
Symptoms
- Check engine light on
- Failed emissions inspection
- Possibly slightly increased fuel consumption
- Sulfur (rotten egg) smell from exhaust under load
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.5–2.5 h
- Emissions test
- Likely to fail
- Parts involved
- Exhaust Temperature Sensor
Related codes
- P0426Catalyst Temperature Sensor Circuit Range/Performance (Bank 1 Sensor 1)
- P042CCatalyst Temperature Sensor Circuit Low (Bank 1 Sensor 2)
- P0437Catalyst Temperature Sensor Circuit Low (Bank 2 Sensor 1)
- P043CCatalyst Temperature Sensor Circuit Low (Bank 2 Sensor 2)
- P0424Heated Catalyst Temperature Below Threshold (Bank 1)
- P0425Catalyst Temperature Sensor (Bank 1, Sensor 1)
- P0428Catalyst Temperature Sensor Circuit High (Bank 1 Sensor 1)
- P0429Catalyst Heater Control Circuit/Open (Bank 1)
- P042ACatalyst Temperature Sensor Circuit (Bank 1 Sensor 2)
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.