OBD-II Code P1168 — What It Means & How to Fix It

What Does This Error Mean?

P1168 means Fuel Rail Pressure Low — Bank 2. On engines where Bank 2 has its own fuel supply or metering, the fuel rail pressure sensor on Bank 2 has detected pressure below the required threshold. Low rail pressure on Bank 2 causes those cylinders to run lean, which leads to misfires, rough running, and poor power on the Bank 2 side. This code is closely related to P0191 and similar fuel pressure codes but is manufacturer-specific to Bank 2.

Affected Models

Vehicles with separate fuel rail pressure monitoring per bank
Common in Nissan and Infiniti vehicles with dual-bank fuel metering
Common in Nissan VQ35 and VQ37 V6 engines in Altima, Maxima, Murano, and Z cars
Common in Infiniti G35, G37, FX35, and EX35 with dual fuel rail circuits

Common Causes

Weak or failing fuel pump unable to maintain adequate pressure on Bank 2 rail
Clogged fuel filter restricting flow to the Bank 2 fuel rail
Faulty fuel pressure regulator allowing pressure to drop on the Bank 2 circuit
Leaking fuel injector on Bank 2 causing pressure loss when a cylinder is not commanded
Failed fuel rail pressure sensor giving a falsely low reading on Bank 2

How to Fix It

Connect a scan tool and check Bank 2 fuel rail pressure in live data. Compare it to the Bank 1 rail pressure if your vehicle shows both.

A significant pressure difference between banks confirms a real Bank 2 pressure issue rather than a sensor fault.
Check and replace the fuel filter if it has not been recently serviced. A restricted filter limits fuel volume to the rail.

Nissan fuel filters on older vehicles are typically under the hood or under the car near the fuel tank.
Test overall fuel pressure with a gauge at the fuel rail. Compare to the manufacturer spec (typically 43 to 51 PSI at idle).

Low pressure across both banks indicates a weak pump. Low pressure only on Bank 2 suggests a regulator or rail-specific issue.
Inspect the fuel pressure regulator. On Nissan VQ engines, the regulator is typically on the fuel rail. Remove the vacuum line and check for fuel in the line.

Fuel present in the vacuum line confirms a leaking regulator diaphragm — replace the regulator.
If pressure and the regulator test normal, replace the Bank 2 fuel rail pressure sensor. The sensor itself may be providing a false low reading.

Always use a new O-ring or sealing washer when installing the replacement sensor.

When to Call a Professional

Fuel filter replacement costs $100 to $200. Fuel pump replacement is $300 to $700 parts and labor. Fuel pressure regulator replacement is $150 to $400. Fuel rail pressure sensor replacement is $150 to $350. Always test actual fuel pressure with a gauge before replacing expensive components.

Frequently Asked Questions

What happens if Bank 2 runs lean from low fuel pressure?

The Bank 2 cylinders receive less fuel than commanded. This causes a lean misfire — the PCM detects this and may set misfire codes alongside P1168. Prolonged lean misfires damage spark plugs and can cause catalytic converter damage from raw oxygen reaching the converter.

Is P1168 common on Nissan VQ engines?

Yes — Nissan VQ-series engines are known to develop fuel pressure issues at higher mileage. Fuel pump wear and regulator degradation are the most common culprits. Regular fuel filter replacement helps maintain proper pressure throughout the pump's life.

Can I drive with P1168?

Short distances at mild throttle are usually possible. However, low fuel pressure causes lean misfires that damage the catalytic converter and cylinders. Do not drive aggressively — get it diagnosed and fixed promptly.