Exhaust Gas Temperature Sensor 1 Bank 1 Out of Range
The P2478 code indicates that the exhaust gas temperature (EGT) sensor 1 on bank 1 is reporting a temperature outside the expected range. This sensor monitors exhaust temperature to protect the catalytic converter and DPF. An out-of-range reading can be caused by a faulty sensor, wiring issues, or actual exhaust temperature extremes.
01. Most Common Causes
- Faulty EGT sensor
- Wiring or connector damage
- Exhaust leak near sensor
- Engine running too hot or too cold
02. Symptoms You Will Notice
- Check Engine Light on
- Reduced engine performance
- Possible limp mode
- Poor fuel economy
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect EGT sensor and wiring for damage.
Step 3: Compare sensor reading with live data; test resistance and voltage.
Step 4: Check for exhaust leaks or other engine issues causing abnormal temperatures.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as it can lead to catalytic converter or DPF damage. Short trips may be okay, but have it diagnosed soon.
How much does it cost to fix?▼
Replacing the EGT sensor typically costs $150-$400 including parts and labor, depending on vehicle make and model.