O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)

What it means

The engine computer has seen the bank 2 upstream oxygen sensor voltage stay low for too long, meaning the sensor keeps seeing a lean mixture on that bank. The mixture may really be lean on bank 2, air may be entering through an exhaust leak, or the signal may be pulled to ground by an electrical fault.

Related codes: P0150P0152P0174P2197P0131

Symptoms4

• Check engine light on.
• Higher fuel consumption.
• Occasionally uneven idle.
• A bank 2 lean code such as P0174 may appear with it.

Possible causes5

• Signal wire shorted to ground or a damaged connector.
• Failed bank 2 upstream oxygen sensor.
• Leak in the bank 2 exhaust manifold ahead of the sensor.
• Lean mixture on bank 2 from an intake gasket leak on that side or a clogged injector.
• Engine computer fault (rare).

How to diagnose5

1. Compare fuel trims between banks; if only bank 2 is high, look for a cause on that side.
2. Briefly enrich the mixture and watch the sensor; if its voltage rises quickly, the sensor is fine.
3. Unplug the connector and check the signal wire for a short to ground.
4. Inspect the bank 2 exhaust manifold for cracks or a failed gasket.
5. Have a smoke test done on the intake on the bank 2 side.

How to fix5

1. Repair the wire shorted to ground or the damaged connector.
2. Repair the bank 2 exhaust leak.
3. Fix the lean cause on that bank, such as an intake gasket or injector.
4. Replace the sensor if it does not respond to enrichment.
5. Clear the codes and confirm the sensor signal and fuel trims return to normal.

Repair cost

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost stays low for a wiring or leak repair, and rises when the sensor is replaced or a real lean cause on bank 2 must be fixed.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026

Frequently asked questions