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The Code Reader

Diagnostic Trouble Code: P0171 System Too Lean Bank 1, P0174 System Too Lean Bank 2 No time to read this article? Listen to it instead! When: DTCs P0171 and/or P0174 are stored when the control unit recognizes that there is too much oxygen in the exhaust based upon readings from the oxygen sensor(s). Why: In

Solving Nissan Performance & Check Engine Light Issues

While we don’t see the amount of coil failures we used to, it seems that the P0171 system lean code is more prevalent than it was in the past. The ECU sets this code when the system has to add more fuel than expected to maintain the desired air/fuel level.

Fuel System FAQ

How do I test the wiring for the fuel pump on a vehicle? What are the symptoms of a clogged fuel filter? What are the signs of E85 contamination? What should I do when I install the new pump and it doesn’t work? Get the answers to these questions and more in this Fuel System FAQ.

Thumping Noise At Cold Start On Honda Accord

Honda Accord owners may report a thump as the ignition switch is released from the start position or as the engine starts. This noise sounds similar to a rubber mallet striking the frame and occurs only on a cold start (the vehicle has been sitting for some time, usually overnight).

Toyota Tech Tip: Rough Idle, Surging Between 500 To 800 RPM

The owner of 2005 Toyota Avalon complains check engine light is on, rough idle and engine idle surging between 500 and 800 rpm. The technician retrieved Diagnostic Trouble Code (DTC) P0171 and P0174 (System too lean banks 1 and 2). The technician replaced the air fuel sensors on both banks and cleared DTCs. After driving vehicle for approximately one mile, all symptoms returned.

Tooling Up For The Diagnostic Process

Automotive trainer John Forro advocates knowing your tooling needs and developing a strong relationship with those tools. Knowing a tool’s capabilities and limitations will help you advance your diagnostic process.

Contaminated Fuel Can Wreck Havoc On Fuel Delivery Systems

Although cases involving contaminated gasoline are relatively rare nowadays, they still occur. In many cases, the technician has replaced the fuel pump or mass air flow (MAF) sensor to address a P0171/P0174 “lean-condition” DTC with no result. In all likelihood, the technician didn’t consider the possibility that the vehicle’s fuel might be contaminated with E85 gasoline, diesel fuel, stale gasoline, or, to a lesser degree, sugar and water.

Using Fuel System Testers To Diagnose Driveability Concerns

Shop owner and automotive trainer Karl Schneider helps you fix driveability concerns, focusing on loss-of-power issues on vehicles with an electric return fuel system.

Troubleshooting Mass Air Flow (MAF) Sensors

Troubleshooting mass air flow (MAF) sensor problems can become a major headache for import technicians because the failure is usually one that involves a calibration error rather than an outright electrical or mechanical failure. Because calibration errors tend to be “gray-area” types of problems, we will begin by looking at the basics of how a “hot-wire” MAF sensor measures airflow through an engine running at various speeds and loads.

Diagnostic Solutions: Contaminated Fuel Can Wreck Havoc On Fuel Delivery Systems

Import Specialist Contributor Gary Goms discusses how contaminated fuel can mimic the symptoms produced by defective fuel pumps, fuel injectors and fuel control components like mass air flow (MAF) sensors. Although cases involving contaminated gasoline are relatively rare nowadays, they still occur. In many cases, the technician has replaced the fuel pump or MAF sensor to address a P0171/P0174 “lean-condition” DTC with no result.