Charged for changing O2 Sensor which wasn't faulty

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elevoria23c, Apr 25, 6:47am
then they tell me it's the fuel injectors that are faulty! The car is a mazda3 2017 with 30K kilms on the clock.
I am very suspicious of the Mazda dealership, any advice would be appreciated as what should or should not do?
franc123, Apr 25, 6:51am
Whats the nature of the problem and is this car NZ new? Unless you have had an issue with fuel contamination its unlikely injectors would be faulty on such a new low km vehicle.
intrade, Apr 25, 6:55am
ok if the fuel injector is faulty then the problem wont go away when they change the o2 sensor.
What the o2 sensor has 1 job and thats to keep enough air and fuel going down the exhaust to keep the catalisator working. So basically it comands the fuel injectors via the engine control unit to dump more or less fuel in the exhaust.
Now if the injectors are faulty the problem will 100% be back soon.
faulty intake holes in system after mass airflow metering divise can also cause the related codes.
also new cars dont have oxigen sensors they have AFR air fuel ratio sensors= they are more tricky to diagnose then a lazy o2 sensor --
vtecintegra, Apr 25, 7:03am
It should still be under the 5 year 'major component and safety systems' warranty anyway
elevoria23c, Apr 25, 7:05am
The car was not running well, hard to start and I think the term is pinging as I accelerated. Kinda pulling as I drove as well
franc123, Apr 25, 7:09am
Yep, and is it NZ new, how long have you owned it, who did you buy it from (private/Mazda agent/other dealer)and is it still under warranty?
elevoria23c, Apr 25, 7:10am
I was advised to take the car to Mazda because they are the experts, they ran a diagnostic scan which they analysed for 3 full hours and came up with a hunch that the O2 sensor needed to be replaced at around $450 for the part.
intrade, Apr 25, 7:11am
pingiging what fuel do you run if 91 then there is your problem
elevoria23c, Apr 25, 7:12am
warranty ran out. I brought it off a little old lady who couldn’t drive it anymore
elevoria23c, Apr 25, 7:12am
95
elevoria23c, Apr 25, 7:13am
car is an import I believe
intrade, Apr 25, 7:15am
The AFR can cause your symptoms if it reports lies. you would leak test injectors and all so this could be 3h labour to diagnose it correct.
The proof will be in the pudding as they say.
intrade, Apr 25, 7:17am
as i said many times modern cars are going to cost a lot that includes toyota vw any new car The more there is to go wrong the more there will go wrong.
franc123, Apr 25, 7:18am
Ok well replacing the 02 sensor clearly hasnt solved the problem has it, there is another issue which is probably upsetting what readings its generating. A chat with the service manager is in order, theyve taken your money for a repair thats not worked. I would not be satisfied with a faulty injector diagnosis at this point, an intake air supply issue or sensor issue is far more likely.
saki, Apr 25, 7:30am
My Mazda 3 had 2 AFR sensors, before and after the cat, theres more than just swapping the part because the dianostic sensor said its kaput.test the sensor check the wiring etc.
elevoria23c, Apr 25, 7:31am
Yes i agree with you. They are the experts so they should know if or what needs to be repaired or replaced.
intrade, Apr 25, 7:46am
if they are experts thats written in the stars or in your case in a comback or not.
franc123, Apr 25, 8:14am
Absolutely. Im sure this issue could be diagnosed easily enough by a good inspection of the engines intake components in conjunction with a proper analysis of the engine management data (this is what is going in and out of the engine control unit). Inaccurate information re how much load the engine is under is highly likely as this upsets how much fuel needs to be injected and of course how much spark advance (ignition timing if you like) is needed. Theres several possible causes of this and a surging pinging engine that lacks power is a typical symptom. If the orange check engine light is coming on at any stage or staying on permanently it must be logging a fault code or codes that should help with narrowing down the cause, it might be a little harder if its not. I would also expect them to be checking that there are no service bulletins applicable to that car for that issue (ie known faults) being a Mazda agency.
andrew1954, Apr 25, 8:45am
Basically the op is saying the new sensor did not fix the problem so should not be charged for it. ok get them to remove the new one and put the old one back. The dealer put the new sensor in thinking it may fix the problem, so they can still charge for fitting and testing it and when it did not fix the problem remove it and put the old one back. what is the time required to remove an old sensor install a new one, remove the new one and put the old one back. So they will remove the cost of the sensor off the bill and add the labour cost of removing the new and refitting the old? .
nice_lady, Apr 25, 9:18am
What the OP is saying, I believe, is that they would expect the dealership to be better at their work than to misdiagnose an issue to the extent of that considerable a cost to the victim - err I mean the customer.

That's close to a weeks wages for some.
gpg58, Apr 25, 10:40am
From a heat pump diagnosis point of view, sensor reading going out of range, and being recorded in memory, is only an indication of where to start looking.
In no way is it gospel that the sensor or component is faulty, (very common mistake made by techs, in thinking it is).
First you have to prove item is actually at fault, as many other things could have caused a sensor to go out of its normal operating range.
For instance a discharge temp sensor may record an out of range event, but be fine, as unit is actually short of gas, meaning little suction cooling for compressor, causing a high temp at discharge sensor.

Assume same applies to any other fault recording system, you have to ask yourself why it may have gone out of range, if it tests ok, not just change it anyway.
But sometimes sensors get moisture in them, which dries out, so tests ok while you are there.
And just changing it anyway fix's the issue.
So its not fixed as to correct way to do things, experience with the items involved sure helps in deciding correct approach, for current system you are working on.
ie its real easy to get it wrong(initially misdiagnose) when trying to find faults, and some take a heck of a lot of hours of testing, to finally find actual cause.
scuba, Apr 25, 10:44am
Did they leave the old parts in the car ? If not maybe they cant re fit the original unless you still have it.
nice_lady, Apr 25, 10:54am
Tell them to replace the injectors BUT at their own cost/risk. Ie: if having replaced them they find that wasn't the issue then they will reinstate the old injectors and you won't be charged for any of that work.
intrade, Apr 25, 11:34am
where did you go in hamilton my mate took his bt 50 to hamilton after he was told by ford taumarunui he needed 7000$ gearbox work and i put my scanner over it and said it looks like the egr valve could be the cause and furter diagnostic with factory scanner is required. Went to hammilton and they did find the same replaced egr and its now fine.
nice_lady, Apr 25, 11:38am
These modern computer controlled cars can be an expensive nightmare to diagnose and repair.