Nissan Sentra 2001 GXE P0171 Code: Causes, Fixes & Recall Information

Was the P0171 code present before refueling? Using fuel injector cleaner can sometimes trigger false codes if used in excess, though it's unlikely. Could you confirm your engine type and current mileage? This helps assess whether the issue is related to fuel system additives or underlying sensor problems.

The code wasn't present before refueling. I'm new to car maintenance, so I thought adding a bottle of injector cleaner would clean the injectors and improve performance. The engine is a QG18DE 1.8L DOHC 16-valve 4-cylinder with cast iron block and aluminum head. Mileage is 120,000 km. Thanks for your help.

How long ago did you add the cleaner? How many kilometers have you driven since then? Was the car running normally before? I recommend clearing the check engine light and refueling with a different brand of gasoline. Then drive under normal conditions again. If the code returns, it may indicate an actual issue—such as vacuum leaks, oxygen sensors, or MAF sensor problems—or simply a false positive due to additive use. Consider checking for other contributing factors.

I added the cleaner about four days ago after refueling. I drove approximately 70 km that day and noticed the check engine light came on. The car was running fine before, and I had it cleared at an auto shop. Unfortunately, the light returned after another 25 km of driving. Thanks for your input.

Check fuel pressure to ensure it's within specifications. Fuel injector cleaners can sometimes clog fuel filters or restrict flow through the system, especially if used in large quantities. The P0171 code may be triggered by this. Also, consider whether the issue is coincidental—some systems may trigger a warning light even when no real fault exists. What brand of additive did you use? This information helps determine if it's a known cause.

I'm experiencing the same P0171 issue on my Lexus IS300. How can I check fuel pressure without tapping into the fuel line or rail directly? Does my car have a test port on the fuel rail, or is there another way to measure it? Also, I believe my vehicle has a fuel filter located in the tank—does that affect performance or cause issues with sensor readings?

Is there a dedicated test port on the fuel rail? If not, you’ll need to install a fuel pressure gauge via a tee connection to measure pressure accurately. This is essential for diagnosing fuel delivery issues that could contribute to P0171.

I own a 2000 Nissan Sentra with the same 1.8L 4-cylinder engine. I previously added fuel injector cleaner several tanks ago and now have a 'Check Engine Soon' light. I've checked battery voltage—charging is normal—and all fluid levels are fine. The car runs smoothly. The light went out temporarily, but returned after refueling with Shell High Octane gas. I suspect a sensor issue, but can't afford a $100+ diagnostic test. Any suggestions for troubleshooting or low-cost checks would be very helpful. Harry

I recently found a recall related to the Nissan Sentra (2000–early 2000s) with QG18DE engines: NHTSA Campaign ID: 03V477000 Component: Electrical System – Ignition Module Manufacturer: Nissan North America, Inc. Defect Summary: The foam used in the interior lining of the Electronic Control Module (ECM) box can out-gas sulfur during curing. If a resistor inside the ECM has surface cracks, this gas may cause corrosion, leading to malfunction indicator light activation, idle instability, poor acceleration, or sudden engine shutdown—potentially resulting in a crash. Corrective Action: Dealers will remove the interior lining material from the ECM box. Owners are advised to contact Nissan at 1-800-647-7261 for notification and service. This recall may explain why some Sentra owners experience sudden check engine light activation or drivability issues, even with no visible mechanical faults.