P0174
Fuel Trim Malfunction (Bank 2)
Powertrain Fuel and Air Metering Long-term fuel trim 🟡 Moderate — Fix within a week
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What This Actually Means
In plain language — no jargon

The engine's computer can't balance the fuel mixture on the right side (Bank 2) of the engine—it's like trying to adjust the seasoning in only half a pot of soup. The oxygen sensor or fuel injector on that side isn't responding correctly to fix the air-fuel ratio.

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Symptoms You May Notice
3 known symptoms for this code
Check Engine Light illuminated
Rough idle or hesitation during acceleration
Poor fuel economy
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECU monitors oxygen sensor feedback from Bank 2 (the side without cylinder #1) and adjusts fuel injector pulse width to maintain a 14.7:1 air-fuel ratio. When long-term fuel trim exceeds ±25%, the ECU cannot compensate further and triggers this fault.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Long-Term Fuel Trim (Bank 2) -10% to +10% >+25% or <-25%
Oxygen Sensor Response Time <100 ms >200 ms or no response
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Engine air filter
Replace a clogged filter to restore proper airflow and reduce trim compensation.
2
Oxygen sensor (Bank 2)
Test with a multimeter; if response is sluggish or stuck, replace the sensor.
3
Fuel injector (Bank 2)
Have injectors professionally cleaned or replaced if clogged, preventing proper fuel spray pattern.