P0171 — Fuel System Too Lean Bank 1
What it means: Fuel System Too Lean Bank 1.
How serious / can you keep driving: Serious. Power derate likely — plan to stop soon.
Check first: Check fuel pressure
Don't risk it — look up listed providers near you and give them this code when you call.
Listed providers nearest Louisville, KY
Closest first. Tell them P0171 and what the truck is doing. RoadService.app lists these providers and does not employ them or carry out the repair.
- 0.0 mi away — based in Louisville, KY · (502) 773-1159
- 0.0 mi away — based in Louisville, KY · (502) 447-1234
- 0.0 mi away — based in Louisville, KY · (502) 648-6725
Seen on: Heavy Truck/Diesel
What P0171 means
Fuel System Too Lean Bank 1. Common causes: Clogged fuel filter or weak injectors.
How serious is it?
Serious. Power derate likely — plan to stop soon.
Most likely causes
- Clogged fuel filter or weak injectors
- Vacuum leak
- MAF sensor fault
- low fuel pressure
First moves (roadside)
- Check fuel pressure
- inspect MAF sensor
- smoke-test for vacuum leaks
FAQ
Fuel System Too Lean Bank 1. Common causes: Clogged fuel filter or weak injectors.
Serious — Power derate likely — plan to stop soon.
The most common cause is: Clogged fuel filter or weak injectors. Other possibilities include Vacuum leak; MAF sensor fault; low fuel pressure.
Power derate likely — plan to stop soon. When in doubt, get a qualified mobile diesel tech on the truck before continuing.
Related codes
Codes that commonly appear alongside P0171, or share the same subsystem.
- Injector Metering Rail 1 Pressure - Data Valid But Below Normal Operating Range (XPI common rail fuel pressure too low) (SPN 157 FMI 1)
- Fuel Delivery Pressure — Low (SPN 94 FMI 1)
- Injection Rail Pressure — Below Normal (SPN 157 FMI 18)
- Injector Metering Rail 1 Pressure - Data Valid But Above Normal Operating Range (XPI common rail fuel pressure too high) (SPN 157 FMI 0)
- Injector #1 open circuit (SPN 651 FMI 5)
- Injector #2 open circuit (SPN 652 FMI 5)
- Injector #3 open circuit (SPN 653 FMI 5)
- Injector #4 open circuit (SPN 654 FMI 5)
Find a mechanic or related guides
General diagnostic guidance for diesel engines (Cummins, Detroit, PACCAR, Volvo, Mack and more). Not a substitute for a scan-tool diagnosis on your specific truck.