Are there any Mazda techs on the board? I have a 2018 Mazda 6 grand touring reserve and have a P0172 code. It says it can be multiple things from MAF, B1S1 Oxygen sensor, fuel injectors. Without paying a ton of money to get it diagnosed are you seeing many of these cars with this issue. Any ideas would be helpful . car has 137k miles. oil changed every 5k miles, did the plugs when it started running rough but didnt help at all.
I have no specific knowledge to add other than 137,000 mi on the original O2 sensors seems questionable
You can disconnect The MAF sensor if it doesn't run much different. The maf is probably bad First place I would look and easiest to swap
Hardly. Mileage of vehicles I have owned or currently own with original O2 sensors: 293,000 255,000 232,000 225,000
I had a slightly older version that gave me fits until I found the crack in the bellows connector between the filter housing and the TB. All kinds of funky behavior because it wasn’t a consistent leak. just something to check.
That crap will give you nightmares trying to find. Hoping since OP have a 2018 the plastic bits are not to that point yet. Fingers crossed
I only do Honda and Toyota cars and on them system too rich codes is usually injectors. System too lean codes usually maf or hose from air filter to throttle body.
I'm a Mazda tech for the last 30 years. P0172 rich bank one. I would be looking at the bank 1 sensor 1 O2 sensor and the injectors. Can you monitor the fuel trims with a scan tool? Make sure the Bank 1 O2 sensor is responding. We put injectors in the direct injected engines all the time.
Bank 1 Sensor is responding. It is 180 degrees higher than bank 2. I can see fuel trim on my scan tool. What should I be looking at? I also have a bore scope so I can look in the cylinders but I don't see any wash in any of them.
This car had a cracked head right over 60k miles from a manufacturing defect. It took them a long time to find it. It took 9 months to get it fixed since none were available at the time.
Rich code means it’s getting excessive fuel from somewhere, if it’s a DI car smell the fuel, most of the time if we see a 172 it’s gas in the fuel from the High pressure pump leaking down. If it’s a car with four oxygen sensors that’s a different story, then it’s either a oxygens sensor or injector dripping. You can tell that by looking at plugs. You can also isolate it by where the fuel trim is off rpm wise. If it’s at idle and gets significantly better under load driving it’s most likely either gas in oil or an injector dripping. If it doesn’t improve I’d start with an Oxygen/A/F sensor.
Look at the ltft and the stft (long term and short term fuel trims) add them. They should add to roughly plus or minus 10% or less. One or the other might be moving around quickly but that is normal. Since it is setting a code for bank one too rich that bank will probably have trims that add up to roughly -20 to 40%.
That means that the computer is reducing the amount of time the injectors are open at that particular load point. Look at both banks and compare them. Drive it around and determine under what conditions the trims go excessively negative.
Most likely you will find that it is at idle and light loads, like barely giving it gas low speeds. If bank 2 looks real good and bank 1 goes negative at idle and light loads then it is not fuel pump or gas oil contamination.
If bank 2 is also going excessively negative and just has not set a code yet then look at the high pressure pump. If it is just bank one you probably have bad injectors especially if it is a direct injection vehicle. I have had no luck cleaning them. I just sent a set to the utrasonic ansu guys with no luck. I had to put new ones in. I am actually putting a new set in a 2019 odyssey today. Dealer quoted him 1370. I’m doing it for 880 and still making 600. Lol
I’m not a mazda/ford man. But I have been doing this for 40 years and own a Honda Acura Toyota Lexus specialty garage.
