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 diesel particulate filter (DPF) from overheating. The out-of-range condition can be caused by a faulty sensor, wiring issues, or actual exhaust temperature extremes due to engine misfires or excessive load.
1. Most Common Causes
- Faulty exhaust gas temperature sensor
- Damaged or corroded wiring/connector
- Exhaust leak near the sensor
- Engine running too hot (overheating, misfire, rich condition)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or limp mode
- Possible increased exhaust emissions
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and freeze frame data.
Step 2: Visually inspect the EGT sensor and wiring for damage or corrosion.
Step 3: Compare sensor readings with a scan tool to expected values at idle and under load.
Step 4: Test sensor resistance and voltage according to manufacturer specifications.
Step 5: Check for exhaust leaks or engine performance issues that could cause abnormal temperatures.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as the engine may enter limp mode or cause damage to the catalytic converter/DPF due to unmonitored temperatures.
How much does it cost to fix?▼
Replacing the EGT sensor typically costs $150-$300 including parts and labor, depending on vehicle make and sensor location.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.