OBD-II code · Powertrain (generic)
P040C EGR Temperature Sensor A Circuit Low
EGR temperature sensor A below lower plausibility — short to ground. EGR mixes inert exhaust into intake to lower combustion peak temperature — too little raises NOx, too much causes misfires and rough running.
Is it safe to drive with P040C?
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
- Pinging or knocking under load
- Power loss and hesitation
- Possible rough idle
- Failed emissions inspection (NOx)
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.5–2 h
- Emissions test
- Likely to fail
- Parts involved
- Egr Temperature Sensor
Related codes
- P040AEGR Temperature Sensor A Circuit
- P041CEGR Temperature Sensor B Circuit Low
- P04D0EGR Temperature Sensor C Circuit Low
- P04E7EGR Temperature Sensor D Circuit Low
- P0409Exhaust Gas Recirculation Sensor "B" Circuit High
- P040BEGR Temperature Sensor A Circuit Range/Performance
- P040DEGR Temperature Sensor A Circuit High
- P040EEGR Temperature Sensor A Circuit Intermittent/Erratic
- P040FEGR Temperature Sensor A/B Correlation
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.