I was driving yesterday (2017 toyotz prius prime) and it wouldnt accelerate on the highway so I pulled over. The electronics were way off. Finally after going and jumping it works. I went to autozone and it says p0171 and p0301. It seems like its the engine recoil or spark plugs. Issue is im working out of town amd drove 2 hours to my parents. Nowhere is open. How would I diagnose this issue and test? Any videos? My dad's pretty handy with cars. ThanksA.
check system fuel pressure first. fuel filter sock may be clogged. you should be able to borrow a gauge kit from any chain auto parts store. also check coolant levels. the exhaust gas heat exchangers are known to develop leaks in that year.
My guess is bad gas... How full is the tank? What is your MPG info telling you compared to info before this problem occurred?
But out of curiosity I asked ChatGPT 5.0 which tries to be extra thorough and supportive and got this answer: Good question — let’s break this down carefully. Your 2017 Toyota Prius Prime is showing P0171 (System Too Lean, Bank 1) and P0301 (Cylinder 1 Misfire Detected). What those codes mean: P0171 (System Too Lean, Bank 1) The engine control module (ECM) is detecting that the air-fuel mixture has too much air or not enough fuel. Common causes: vacuum leaks, intake leaks, dirty MAF sensor, weak fuel pump, clogged fuel injector(s), or exhaust leaks upstream of the O₂ sensor. P0301 (Cylinder 1 Misfire Detected) A misfire is being detected specifically on cylinder 1. Common causes: bad spark plug, failing ignition coil, fuel injector issue, compression problem (valves/rings/head gasket), or a symptom of a lean condition (ties back to P0171). How these might be related: Since both codes are showing up, the likely scenario is: Cylinder 1 is misfiring, which can cause excess oxygen in the exhaust, tricking the ECM into thinking the mixture is lean → triggers P0171. Or vice versa: a lean condition (fuel delivery/vacuum leak) is disproportionately affecting cylinder 1, causing the misfire. Step-by-step confirmation: Here’s how I’d approach diagnosing it: Check for obvious vacuum/intake leaks Listen for hissing around intake manifold, vacuum hoses, and PCV valve. Spray carb cleaner or use smoke test to check for leaks that can cause lean condition. Inspect ignition system on cylinder 1 Pull spark plug (check gap, wear, fouling, cracks). Swap ignition coil from cylinder 1 to another cylinder. If misfire code moves (e.g., becomes P0302), the coil is bad. Check the fuel injector on cylinder 1 Listen with a stethoscope for injector clicking. If possible, swap injector between cylinders to see if misfire follows. Consider professional flow testing if injectors are suspected. Airflow sensors & exhaust sensors Inspect/clean the MAF sensor (dirty MAF is a very common P0171 cause). Check O₂ sensor readings with a scan tool — is the upstream sensor showing lean consistently? Fuel system pressure test Confirm the fuel pump is supplying correct pressure (weak pumps cause lean codes and misfires). Compression test (last resort if ignition/fuel/vacuum are fine) Ensure cylinder 1 isn’t suffering from low compression due to valve, piston ring, or head gasket issues. Most common real-world fixes for this combo on a Prius: Dirty or failing MAF sensor → clean or replace. Failing ignition coil on cylinder 1. Bad/dirty fuel injector on cylinder 1. Vacuum leak at intake manifold gasket near cylinder 1.
After reading what ChatGPT said I'm reminded of a slightly older PriusV that drove me crazy for weeks with similar symptoms and it turned out to be a vacume line on the engine that failed. So wiggling hoses in the engine compartment with these symptoms is now a top priority for me.
