P2478 Possible Causes
- Faulty Exhaust Gas Temperature Sensor (EGTS), Bank 1 Sensor 1
- Exhaust Gas Temperature Sensor, Bank 1 Sensor 1 wiring harness is open or short-circuited
- Poor electrical connection in Bank 1 Sensor 1 Exhaust Gas Temperature Sensor circuit
- Exhaust leaks
- Excessive particulate buildup on the sensor
How to Fix Code P2478
Check the “Possible Causes” listed above. Visually inspect the wiring harness and related connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.
P2478 Possible Symptoms
Illuminated engine light (or service engine soon warning light)
P2478 Meaning
The Powertrain Control Module (PCM) continuously monitors the Exhaust Gas Temperature Sensor (EGTS) for proper circuit continuity and out-of-range high values. The EGTS is located upstream of the Diesel Oxidation Catalyst (DOC) and/or upstream of the Diesel Particulate Filter (DPF). The EGTS detects exhaust gas temperature and converts it to voltage, sending it back to the PCM with the voltage signal to control engine conditions for effective emission reduction. The PCM sets OBDII code P2478 when the exhaust gas temperature sensor is outside factory specifications.