My Cart

No items in cart

This is a demo. Do NOT enter real credit card information!

If you wish to test this functionality, refer to these instructions.

How to Fix a P0171 code on GM 1.4L Engines

The GM 1.4L turbo charged 4-cylinder engine, commonly found in the Chevy Sonic, Cruze and Buick Encore, has a well-known issue resulting in a lean code, P0171, and often times oil consumption and/or an engine whistle noise. This issue is often only partially repaired resulting in repeat failures. Below you’ll find the process for diagnosing and repairing the root cause resulting in a properly fixed vehicle the first time.

Article contents

Identifying symptoms and possible cause
Testing for common PCV valve issue
Checking for root cause of PCV failure
P0171 repair procedure
Confirm P0171 fix

Identifying symptoms and possible cause

Symptoms for this issue can include an engine lean condition with a P0171 code, Oil consumption and/or an engine whistle noise
Check if vehicle is currently experiencing any of the symptoms above
If the vehicle has symptoms present, test the positive crankcase ventilation (PCV) valve for a ruptured diaphragm according to testing procedure below

Testing for common PCV valve issue

Difficulty: 1/5
Time required: 5 minutes
Tools Required: Piece of paper or tissue

Remove the engine cover and locate PCV valve

With the engine running at idle, hold a small piece of paper or tissue in front of port. If the paper is drawn to the port, vacuum is present and the PCV valve is faulty

If the PCV valve has failed, the valve cover needs to be replaced but may not be the root cause of failure. Use the test below to test for a possible root cause of PCV valve failure

Checking for root cause of PCV valve failure

Difficulty: 1/5
Time required: 10 minutes
Tools Required: Flashlight

Locate and remove the PCV bypass tube from the intake manifold

Using a flashlight look down the intake manifold bypass tube port and check for missing non-return valve

Tip : Oil and carbon build up may make the non-return valve dirty and harder to see

Compare to photos below to determine if non-return valve is missing

Known good non-return valve (still in place)

Known bad non-return valves (missing)

P0171 Repair Procedure

Difficulty: 3/5
Time required: 2 hours
Tools Required:

Parts Required:

Intake manifold

Valve cover

RTV Silicone

PCV Bypass Tube*

*indicates if broken

Remove intake manifold

Tip: An E10 Torque socket is required to remove intake manifold bolts

Make sure to disconnect the small vacuum line and the wiring harness before attempting to remove the intake manifold

Remove the valve cover by removing the bolts using the E10 socket

Clean up all the gasket mounting surfaces making sure to remove all oil residue

Installation

Apply RTV sealer to the seams where the timing cover meets the engine block

Install the valve cover and torque bolts to 71 inch pounds using sequence below

Swap over the throttle body, fuel rail, and map sensor to new intake manifold

Tip: Make sure to reconnect small vacuum hose and wiring harness on intake manifold

Install the intake manifold and torque bolts down to 15 foot pounds
Re-install all the wiring and hoses to the valve cover and the intake manifold

Tip: Check PCV bypass hose for O-ring before installing

Confirm P0171 Fix

Use a small piece of paper to confirm that vacuum is no longer present at the PCV valve port

If a scan tool is available, you can also monitor fuel trims and confirm they drop down to +/- 10%

For more information, questions, or help diagnosing your vehicle, contact the GoTech technical support team via phone or chat below.