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2006 Sedona LX 3.8L - Limp Mode & Blinking CEL: OBD2 Codes 0171, 0174, 0300, 0331 Explained

Model: Sedona LX Fault Code: P0171 Posted: 2016-02-14 21:56

I recently purchased a 2006 Toyota Sedona LX (3.8L V6) on February 13, 2015, in a cash deal from a dealer for my wife. After driving approximately 100-150 miles with no issues, I parked the vehicle for about an hour and noticed two diagnostic trouble codes: - 0171 - System Too Lean (Bank 1) - 0174 - System Too Lean (Bank 2) No noticeable symptoms at that time. However, later that day, my wife reported the Check Engine Light began flashing and the vehicle entered limp mode — it would only accelerate within a specific RPM range and then shudder before requiring a stop. She was able to turn off and restart the engine, which temporarily resolved the issue. After driving just a few hundred feet, the symptoms returned. I scanned the vehicle again and found additional codes: - 0300 - Random/Multiple Cylinder Misfire Detected - 0331 - Knock Sensor 2 Circuit Range/Performance (Bank 2) - 2039 - Reductant Injection Air Pressure Sensor Circuit Low Input The vehicle is currently in limp mode, and I suspect this may be related to fuel delivery issues or sensor malfunctions. Possible root causes include a faulty oxygen sensor, vacuum leak, dirty Mass Air Flow (MAF) sensor, or misfire due to ignition or engine timing problems. I visited a local Quick Lube shop in Lakeland, Florida, where they performed an oil change using high-mileage oil and completed a transmission fluid flush. They noted the vehicle 'burped' during operation — transmission fluid splashed onto their shirt — and advised returning for a follow-up check in one week to confirm fluid levels. I'm seeking advice from experienced owners or mechanics familiar with the 2006 Sedona LX's 3.8L engine system, especially regarding limp mode triggers and how to interpret these OBD2 codes. Are there known common issues with this model year? Could the transmission flush have contributed to the current fault? Any recommendations for troubleshooting steps (e.g., vacuum leak test, MAF cleaning, live data monitoring) would be greatly appreciated.

Related fault codes
P0171P0172
Comments (5)
Anonymous 2016-02-15 08:13

Did you just purchase this vehicle or was it several years ago? If it's from 2015, why not address the issue with the dealer — was it a Kia dealership? The code prefixes should be included (e.g., P-codes), especially for codes listed as 'null'.

Anonymous 2016-02-15 10:37

Apologies for typos. This vehicle was purchased just a few days ago via Craigslist, no warranty. All codes are indeed P-codes. The entries labeled 'null' match exactly what Torque (a Bluetooth OBD-II scanner app) describes as 'no data available'.

Anonymous 2016-02-15 11:07

Is the vehicle currently drivable? Try getting a free OBD2 scan at most auto parts stores — it's quick, affordable, and provides a second opinion on your codes. I'm not familiar with 'Torque' but I believe it's an Android app that connects to Bluetooth OBD-II scanners and supports live data monitoring (like fuel trims, MAP, and O2 sensor readings). A vacuum leak test using the traditional spray method can help identify intake leaks — check all hoses and mating surfaces. A fuel pressure test or a pressure leak-down test at idle might also be useful, though these require access to a Schrader valve or proper equipment. We can discuss limp mode in more detail later.

Anonymous 2016-02-15 11:24

I apologize for the typos in my original post. I plan to clean the MAF sensor and inspect all intake and vacuum hoses for leaks. Torque is a mobile app that connects via Bluetooth to OBD-II readers. It supports live data monitoring, though I'm not fully confident about its real-time accuracy or depth of diagnostics. Could the Quick Lube service have caused any damage? They drained old oil, refilled it, and had me go through all gears multiple times — then turned off and restarted the engine. They mentioned the transmission fluid 'burped' during operation (splashed on their shirt), and advised returning in a week to verify fluid levels remain stable.

Anonymous 2016-02-15 11:37

At this point, there's no indication that the transmission is at fault — the transmission will display its own codes if it were malfunctioning. The current symptoms are more likely engine-related and should be addressed through diagnostic testing of fuel trim, misfire, and sensor performance.