OBDII trouble code P0171 is a diagnostic code that signifies a problem with your vehicle’s fuel delivery system. The correct and specific language of this trouble code is Fuel System Lean, Bank 1. Today we’ll be showing you how to resolve your lean condition in a VQ35DE by showing you how to replace a VQ35 Fuel Pressure Regulator.
Because this DIY article involves fuel and the process of disconnecting and removing fuel components, do not continue if you feel uncomfortable working on your vehicle. For a complete guideline on safety and rules to adhere to when working on your car, check our guide here.
Possible causes of P0171
- Bad fuel pressure regulator
- Bad fuel pump
- Faulty MAF sensor
- Faulty ECU
- Clogged injector
Because there can be other reasons for this P0171 OBDII trouble code, we suggest you check our other guides on repairing the VQ35. DIY articles like How To Test a VQ35 MAF, Crank Position Sensor, Camshaft Position Sensor or How to locate your VQ35 ECU. Other trouble codes may accompany your P0171 OBDII trouble code, such as P0174 Bank 2 lean or P0300 Engine Misfire.
Before you begin our replace a VQ35 Fuel Pressure Regulator DIY guide, you’ll need to open your gas tank and remove the gas cap. Doing so will allow the excess pressure in your fuel system to escape, which will hopefully make much less of a mess.
In order to reach your fuel pressure regulator, you will need to clear the passenger side of your VQ35DE. We are working in a 2006 Nissan 350Z, and our DIY article assumes you have already removed the plastic engine cover by unbolting the 10mm nuts and bolts from the intake manifold.
Your 3.5 liter VQ35 has two fuel pressure dampers that work in conjunction with each other. Shown above is the regulator on the Bank 1 side, which represents the side of the engine cylinder 1 is on. Begin our How To Replace a VQ35 Fuel Pressure Regulator by undoing the plastic clips that hold your engine wiring harness in place on the passenger side.
If your OBDII trouble code is P0174 and you need to service the fuel pressure regulator on your drivers side, skip ahead to the crossover pipe and secondary fuel pressure regulator images.
Once you have these harnesses pushed aside and have gained the proper clearance, go ahead and undo the 10mm bolts that hold your primary fuel pressure regulator in place.
Make sure to use the proper eye wear and protection as the fuel in this line is under high pressure. Once you have this fuel pressure regulator removed, you can go about disconnecting the fuel pressure regulator from the car. You can either elect to try and remove the fuel line from the regulator or disconnecting the line from the junction on the frame.
If you happen to tear, pinch or otherwise damage this line make sure to replace with a fuel rated line that will not fail. Your replacement fuel pressure regulator is Nissan OE part number 22675-AM600 or 22675-AM60A and this FPR usually comes with the line that quick connects to the hardlines on your frame.
If you have a lean condition in Bank 2 or the driver side of the engine, here’s the crossover pipe to the secondary fuel pressure regulator. Note how all these regulators and dampers are connected and secured by way of 10mm bolts.
The replacement fuel pressure damper for the drivers side fuel pressure regulator is Nissan part number 22675-5Y760 or 22675-5Y76A. After replacing and servicing the fuel pressure regulators in question, make sure to check for any leaks before starting the vehicle.
Get into your Nissan or Infiniti G35 or 350Z and turn the key to the “ON” position to pressurize the fuel system. Run your hand behind your intake manifold plenum and under the fuel pressure regulator mounting points to inspect for moisture or possible leaks.
Replace the fuel pressure regulator grommets and orings if a leak is present. Always double and triple check for possible fuel leaks before starting your VQ35. You now know how to replace a VQ35 Fuel Pressure Regulator to resolve the Lean OBDII trouble codes of P0171 or P0174. Have a question about replacing VQ35 Fuel pressure regulators? Leave us a message below!
