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I have a 2000 Hyundia Sonata with 2.5L engine which is not able to pass its self emissions test. According to my Bluedriver scanner it has a U0d00 code and 0-0.03 reading on the MAF sensor. LTFT's are stable at -14% both banks and trending towards 0 very slowly. It runs in closed loop mode and I don't have a MAF trouble code. I have removed the MAF sensor and bench tested it and the 0-5 vdc output seems pretty reasonable. I have checked the wiring to the ECU and it seems fine. I disconnected the MAF and it seemed to have no impact on the ECU's function or readings. I have replaced the ECU with a used model and I still get a solid 0.0 for MAF sensor readings (With the original ECU I got 0-0.8, replacement is a solid 0.0) . I cut the signal wires to the ECU and applied 0-5 VDC right to the replacement ECU and I get nothing. Any thoughts on what to try next? Park it on railroads tracks is all that comes to mind at the moment.
Is this a car a customer has brought in or your own?
It's always good to know the history, whether they have replaced a part already [like the MAF sensor] and fitted the correct one, if the terminals are in the wrong place what you think is sensor out could actually be 5v in or something.
I recently had a 2016 Holden Colorado that wouldn't start. No readings from the MAF sensor besides a 0.2v that the ECU put out itself when cranking. I swapped MAF sensors with a slightly older Holden Colorado and same issue, and later found they aren't compatible anyway. It turned out the MAF sensor itself was faulty but the newer model didn't have the ability to throw a code for a bad MAF sensor, even when it was unplugged. So much for 'advancing technology'.
Getting involved in discussions because I have a lot to learn still.
This is a personal car that is recently in my possession again.
I don't believe the MAF sensor has every been replaced.
I have checked the wiring and signals is per a wiring diagram. I recently cut the signal wires and tied in my DC voltage generator and the ECU's do not read it. The wire sockets seem to be in good order as well.
The question is 'how reliable is your scan too?l'. I've seen even the expensive scan tools give the wrong readings on live data, simple because they can't actually access it - they just throw up a random number or "0" for the reading.
Getting involved in discussions because I have a lot to learn still.
I have low confidence in the scan tool as it is new to me (I haven't developed trust yet) and I don't have a history on this car with the scanner. I did try a second scan tool and got the same results. Tonight I'm trying an old Snap on scanner as a third tool.
I did strengthen my suspicion of the MAF sensor's circuit by driving with the sensor off and I didn't see any changes in the ECU's or car's performance. LTFT's stayed steady at -14%.
My primary goal is the car passes emission inspection. I believe the MAF is preventing that. Instead, it may be that Hyundai doesn't complete it's test easily.
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