What Does P2478 Mean?
The exhaust gas temperature at Bank 1, Sensor 1 (pre-catalyst or turbo outlet) is reading outside the expected range for current operating conditions. The PCM detects either excessively high or low temperatures compared to fuel delivery and load calculations.
Common Causes
40%
Faulty EGT sensor providing inaccurate readings
25%
Exhaust leak before sensor location affecting readings
15%
Failed or failing turbocharger affecting exhaust temperatures
12%
Incorrect fuel mixture causing abnormal EGT
8%
Clogged DPF or catalytic converter creating backpressure
Diagnostic Steps
1
Step 1: Monitor live EGT data at Bank 1 Sensor 1 and compare to expected values for engine load and RPM
2
Step 2: Inspect exhaust system for leaks upstream of sensor location using visual and audible checks
3
Step 3: Compare EGT readings across all sensors to identify anomalies specific to this sensor
4
Step 4: Test sensor resistance and response time using multimeter and heat source
5
Step 5: Check for exhaust restrictions and evaluate turbocharger operation if applicable
Estimated Repair Cost
$200 - $800
Parts + labor, varies by vehicle and location
The exhaust gas temperature at Bank 1, Sensor 1 (pre-catalyst or turbo outlet) is reading outside the expected range for current operating conditions. The PCM detects either excessively high or low temperatures compared to fuel delivery and load calculations.
The most common cause of P2478 (Exhaust Gas Temperature Out of Range Bank 1 Sensor 1) is: Faulty EGT sensor providing inaccurate readings
Typical repair costs for P2478 range from $200 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive short distances but may cause turbo damage or catalyst failure if temperatures are genuinely excessive. Monitor for power loss or unusual exhaust smoke.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P2478 to identify the root cause.
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Quick Info
Category
Powertrain
System
Emissions Control System
Difficulty
Type
Generic (SAE)
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