What Does P0172 Mean on Your 2019 Ford Explorer?
If your 2019 Ford Explorer is throwing a P0172 code, it means the engine control module (ECM) has detected that Bank 1 of the engine is running too rich. In plain terms, there is too much fuel or not enough air in the combustion mixture. The 2019 Explorer comes with either the 3.5L Ti-VCT V6 or the 2.3L EcoBoost turbocharged four-cylinder, and both engines can trigger this code for similar reasons.
Running rich wastes fuel, can foul spark plugs, and over time can damage your catalytic converter. It is worth investigating as soon as possible so you do not end up with a bigger repair bill down the road.
Common Symptoms You May Notice
- Check engine light illuminated on the dashboard
- Decreased fuel economy, sometimes noticeably worse
- Rough idle or engine stumbling at low RPM
- Black smoke from the exhaust, especially on acceleration
- Strong fuel smell from the tailpipe
- Failed emissions inspection
Top Causes of P0172 on the 2019 Explorer
- Dirty or faulty mass airflow (MAF) sensor - The MAF sensor on the 2019 Explorer is located between the air filter box and the throttle body. A contaminated MAF sensor underreports airflow, causing the ECM to inject too much fuel. This is the number one cause of P0172 on this vehicle.
- Leaking or stuck-open fuel injector - A fuel injector that does not close properly will drip extra fuel into the cylinder. On the 3.5L V6, Bank 1 injectors are on the passenger side of the engine.
- Faulty oxygen sensor (Bank 1 Sensor 1) - A sluggish or failed upstream O2 sensor on Bank 1 can send incorrect readings, causing the ECM to add fuel when it should not.
- High fuel pressure - A failing fuel pressure regulator or restricted fuel return line can push excessive fuel through the injectors.
How to Diagnose the Problem
Start with the basics. Pull the code with an OBD-II scanner and check for any additional codes. Look at the short-term and long-term fuel trims on Bank 1. If long-term fuel trim is negative 15 percent or more, the engine is confirming a rich condition.
Inspect the air filter first. A clogged filter restricts airflow and can cause a rich condition. Next, remove the MAF sensor and clean it with dedicated MAF sensor cleaner spray. Do not use carb cleaner or brake cleaner, as these can damage the delicate sensing element.
If cleaning the MAF does not resolve it, check the O2 sensor waveform with a scan tool. A healthy upstream sensor should oscillate between 0.1V and 0.9V. If it sits high (above 0.45V most of the time), the engine is running rich and the sensor may or may not be the cause.
Check fuel pressure with a gauge. The 2019 Explorer should read approximately 55-60 psi at idle. If pressure is significantly higher, suspect the fuel pressure regulator.
Repair Options and Cost Estimates
- Clean or replace MAF sensor: Cleaning is essentially free if you buy a $8 can of MAF cleaner. Replacement MAF sensor runs $50-$150 for the part, plus $50-$100 labor if you have a shop do it.
- Replace fuel injector: Parts cost $30-$80 per injector. Labor can range from $150-$300 depending on accessibility.
- Replace upstream O2 sensor: Parts are $50-$150. Labor is typically $80-$150.
- Replace fuel pressure regulator: Parts run $50-$120 and labor ranges from $100-$250.
Can You Fix This Yourself?
Cleaning the MAF sensor is a very beginner-friendly repair. It takes about 15 minutes and requires only a screwdriver and MAF cleaner spray. Replacing the MAF sensor or an O2 sensor is also within reach for most DIY mechanics with basic hand tools. Fuel injector replacement is more involved and typically better suited for intermediate-level DIYers or a professional shop.
Prevention Tips
- Replace your engine air filter every 15,000-20,000 miles to keep the MAF sensor clean
- Use quality fuel from reputable stations to reduce injector deposits
- Consider using a fuel system cleaner additive every 5,000 miles
- Address any check engine light codes promptly before secondary damage occurs