P1158

Bank 2 Fuel Control Shifted Lean

Powertrain Fuel and Air Metering Lean condition - Bank 2 🟡 Moderate — Fix within a week ⚠️ Drive with Care
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What This Actually Means

In plain language — no jargon

The engine computer detected that Bank 2 is running too lean (not enough fuel), like trying to drive uphill with the gas pedal barely pressed. The oxygen sensor readings suggest the fuel mixture can't be corrected by normal adjustments.

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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 and reduced engine performance
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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The ECU monitors Bank 2's oxygen sensor voltage to maintain proper fuel-air ratio. When the sensor consistently reads lean (high voltage) and the ECU's fuel trim corrections max out, it indicates a persistent lean condition the system cannot compensate for.

Voltage & Parameter Thresholds

ParameterNormal RangeFault Condition
O2 Sensor Voltage (Bank 2) 0.4-0.6V (switching around 0.5V) Consistently >0.7V with maxed fuel trim
Long-term Fuel Trim (Bank 2) -10% to +10% >+20% (ECU adding excessive fuel)
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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex
1
Air intake leak sealant or hose clamps
Inspect and seal any vacuum leaks around intake manifold and hoses on Bank 2 side.
2
Fuel injector (Bank 2)
Clean or replace the Bank 2 fuel injector if clogged; use fuel system cleaner first.
3
Oxygen sensor (Bank 2)
Replace the upstream O2 sensor on Bank 2 if voltage reading is erratic or stuck high.
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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code P1158 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.

Safety note: OBD-II codes identify the system or circuit where a fault was detected — they do not always identify the exact failed component. A professional mechanic using live sensor data will diagnose the root cause more accurately than replacing parts based on the code alone.
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How to Clear Code P1158

What happens after you fix the fault

Once the fault is repaired, P1158 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.

The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.

✅ Safe to Clear When
  • Fault has been diagnosed and repaired
  • You want to confirm the repair worked
  • Code appeared after a sensor was cleaned
⚠️ Do Not Clear When
  • Preparing for an emissions/PUC test
  • Root cause is still undiagnosed
  • Check engine light is flashing
Emissions test note: Clearing codes resets OBD readiness monitors. Most vehicles need 50–100 km of mixed driving before monitors complete. Do not clear codes immediately before an emissions or PUC inspection.