P0171 Code - Which means, Causes, Signs (& How To Repair It)

A P0171 code seems within the engine management unit when the Oxygen sensor on financial institution 1 acknowledges a too lean air-fuel combination for the sensor to right it.

A number of various things may trigger this hassle code. Here's what it's essential know in regards to the P0171 code.

Code Definition

P0171 – System Too Lean (Financial institution 1)

What does the P0171 code imply?

The P0171 code signifies that the Oxygen (O2) sensor on financial institution 1 acknowledged a too lean combination to right it.

The Oxygen O2 sensors have the flexibility to right a gasoline combination of +-15%. If it must right the air-fuel combination greater than that, the P0171 code might be saved.

P0171 Signs

If the gasoline combination is barely lean, you'll typically get no different signs from the P0171 code apart from the verify engine gentle in your dashboard. If the gasoline combination is very lean, chances are you'll get any of the next signs:

How severe is the P0171 Code?

Average – Most often, the lean combination is important, and you'll not discover any distinction within the engine’s efficiency. Different instances your automotive engine may very well run so lean that your engine elements are in peril on excessive load.

It could be the primary signal of one thing that may fail extra quickly, like a clogged gasoline filter or a failing gasoline pump.

It's okay to drive for brief distances to the workshop, however ignoring the code and proceed to drive might trigger integral engine elements to take harm.

P0171 Causes

The P0171 tells us that there's a lean air-fuel combination, nevertheless it doesn’t inform us what may trigger a lean gasoline combination. There are literally many alternative issues that may trigger a lean combination. The next points will be brought on by the P0171 code:

What repairs can repair the P0171 code?

There are lots of totally different options for the P0171 code as a result of there will be so many alternative causes. Listed below are the commonest fixes to the P0171 code. Most typical from the highest.

• Substitute defective vacuum hoses or gaskets across the consumption
• Restore different consumption leaks
• Substitute PCV Valve
• Substitute the gasoline pump/gasoline filter/gasoline strain regulator or restore wirings
• Substitute EVAP valve
• Substitute O2 sensor(s)
• Substitute EGR valve
• Substitute MAP/MAF sensor
• Restore exhaust leak
• Substitute coolant temperature sensor
• Restore defective wirings
• Substitute ECM/PCM (uncommon)

Frequent Analysis errors

A standard diagnostic mistake is to begin changing elements with out making a correct analysis. Most often, the P0171 code is brought on by one thing simple as a vacuum leak or a foul PCV valve. For those who begin changing MAF sensors, O2 sensors, and so forth., you'll most likely spend some huge cash with out outcomes.

A defective O2 sensor just isn't a quite common reason behind the P0171 code, even when many individuals begin to substitute it straight after they see this code.

Beneficial Instruments for Analysis

• Diagnostic OBD Scan Software
• Multimeter
• EVAP Smoke Machine
• Gas Stress Tester
• MAF Sensor Cleaner
• Primary Hand Instruments
• Auto Restore Guide
• Electrical Contact Cleaner

Learn how to diagnose the P0171 Code

Diagnosing the P0171 code is straightforward in case you have the suitable instruments to do it. It's most frequently not simple to diagnose the P0171 with out these instruments. This information is made for professionals with entry to those instruments. Most often, you may lend these instruments at a workshop should you ask properly.

1. Join an OBD2 scanner to your automobile. Recheck the difficulty codes and discover every other associated hassle codes that might trigger a lean combination. Comply with the diagnose process on the opposite hassle code should you get any.
2. Test the reside information for the MAF sensor, temperature sensors, and determine if their indicators are logical or means out of vary.
3. Join an EVAP smoke machine to your automotive’s inlet and verify for any consumption leaks. Test the PCV valve and the EVAP purge valve. One can find a leak or a defective one-way valve that's inflicting the P0171 code typically.
4. Test the gasoline strain. Join a gasoline strain gauge to the gasoline rail and guarantee that the gasoline strain is right. Whether it is too low, verify the gasoline filter, gasoline pump, gasoline strain, and regulator.
5. Test the EGR valve. An EGR valve caught open could cause the air-fuel combination to remain lean. If potential, attempt to verify the valve inside it whilst you open and shut it together with your diagnostic device.
6. Clear the MAF sensor. A unclean MAF sensor could cause the air-fuel combination. Examine it and verify for any dust on the sensor. After it, you need to attempt to clear the difficulty codes and verify if the code comes again. It may additionally be broken, so verify its values on idle and on strain and substitute it if defective.
7. Test for exhaust pipe leaks earlier than the O2 sensor. Restore the leaks should you discover any.
8. If the issue nonetheless happens and also you haven’t discovered any issues with the talked about elements above, it's time to diagnose your O2 sensor. For those who discover it giving incorrect values – substitute it.

Estimated Price of Restore

Listed below are some examples of the restore prices of the P0171 code. The costs are together with elements and labor. It doesn't embody analysis prices.

• Vacuum Hose alternative – 10$ to 50$
• O2 sensor alternative – 200$ to 300$
• PCV Valve alternative – 20$ to 60$

Frequent Associated Questions