P0548
Exhaust Gas Temperature Sensor Circuit Low - Bank 2 Sensor 1
Powertrain Emission Controls EGT Sensor Fault 🟡 Moderate — Fix within a week
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What This Actually Means
In plain language — no jargon

The exhaust temperature sensor on bank 2 (passenger side) is sending a signal that's too low, like a thermometer stuck reading cold when it's actually hot. Your engine's computer can't properly monitor exhaust temps, which affects emission controls and engine performance.

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Symptoms You May Notice
3 known symptoms for this code
Check Engine Light illuminated
Reduced fuel economy or rough idle
Possible black smoke from exhaust or rich running condition
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECU monitors voltage from the exhaust gas temperature (EGT) sensor on bank 2, cylinder 1. The sensor should produce a voltage that rises proportionally with exhaust heat. When voltage falls below the expected threshold (typically below 0.5V at operating temp), the ECU detects a circuit-low fault.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
EGT Sensor Voltage 0.5V - 4.5V (varies with temp) Below 0.5V or open/short circuit detected
Exhaust Temperature 300°C - 800°C at cruise Signal implies temp below sensor minimum
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Wiring harness and connectors
Inspect connector at bank 2 sensor 1 for corrosion, loose pins, or damaged wires; clean or reseat as needed.
2
EGT Sensor Bank 2 Sensor 1
Unbolt the sensor from the exhaust manifold and install a new OEM or quality replacement, ensuring proper torque.
3
ECU or PCM reprogramming
If wiring and sensor are good, reflash or replace the engine control module at a dealer.