Exhaust Gas Temperature Sensor Circuit Low (Bank 2 Sensor 1)
The P0548 code indicates that the Engine Control Module (ECM) has detected a low voltage signal from the exhaust gas temperature (EGT) sensor located on Bank 2, Sensor 1 (pre-catalyst). This sensor monitors exhaust temperature to protect the catalytic converter and DPF from overheating. A low circuit condition typically means the signal voltage is below the expected range, often due to a short to ground, faulty sensor, or wiring issues. This can lead to incorrect temperature readings, potentially causing regeneration issues in diesel engines or reduced performance in gasoline engines.
1. Most Common Causes
- Faulty exhaust gas temperature (EGT) sensor or internal short circuit
- EGT sensor wiring shorted to ground
- Corroded, bent, or poorly connected EGT sensor connector
- Open signal circuit between the sensor and the ECM
- Internal ECM failure
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or power
- Increased fuel consumption
- Possible limp mode activation
- Failed emissions test
3. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for additional codes.
Step 2: Visually inspect the EGT sensor and wiring for damage, corrosion, or loose connections.
Step 3: Measure sensor resistance and compare to manufacturer specifications (typically 100-200k ohms at room temperature).
Step 4: Check for short to ground by disconnecting the sensor and measuring voltage at the harness connector (should be ~5V reference).
Step 5: If sensor and wiring are okay, test the ECM output or replace the sensor.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as the ECM may limit engine power or enter limp mode to protect the exhaust system. Continued driving could cause catalytic converter or DPF damage.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on the vehicle and sensor location. DIY replacement can be cheaper if you have the tools.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.