Random powertrain light.

[Klhumrich]

Hey guys, new on here and im in need of some help! I have a 98 BMW 318ti hatchback. Problem is a powertrain light came on when driving down the highway at 80mph and when the light came on the transmission did a very light jerk, so I got off the highway and at a stop in drive the car idled weird and at park it was fine and normal then just turn the car off for a few then went on my way. Then did it again. So I got to my destination and unhooked the battery (for a day) and reset the car. Drove it for a day and it was perfectly fine. Next day it did it again. So when the light does come on the transmission acts all funny But, when the lights off, it drives normal. So I parked it left it alone for a few day and now whenever I turn the car on the light is automatically on. Also abs and asc light where on before any of this happen And check engine light. Scan tool says vss and maf sensor. Sorry for the long message. Thanks guys!

[dworthy]

Welcome to the Forum!

Okay, most scan tools provide a code, please post up that code. Also provide exact wording of each code, now most tech don't like "P" codes, so be aware.

Yes a problem with the engine can set a transmission light just so you know.

Lastly pull the codes for the ABS so we can work thru that as well.

[Klhumrich]

Well my abs is not connecting to the scanner. Abs and asc light was off when I bought the car (few months back). But shortly after I bought it the abs and asc light would come and go. Now it's on permanently. The obd2 codes are for the, mass airflow circuit A(P0102) and the Vehicle Speed Sensor (P0500).

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[bmwdirtracer]

Well, the ABS can't work without vehicle speed.
The transmission can't work correctly without proper data from the engine computer for engine torque and intake air mass....or Vehicle speed.

You can't diagnose the car with a P-code reader. That device can only tell you government emissions codes, nothing useful.

I recommend that you get all the BMW specific codes read with a good BMW specific scan tool, get a smoke test of the intake / ccv system done with a smoke machine, and watch the live data for that Mass AirFlow sensor with the same good diagnostic scan tool.

A generic scan tool cannot possibly connect with the ABS system and other computers of your car. This can only be done with a BMW specific tool, and connected to the 20-pin diagnostic port underhood.

[dworthy]

+1

Chris tends to hit it on the head.

Does the Speedometer work? What I would look at and test is the Left Rear ABS sensor, and the MAF. The MAF probably could use a cleaning too. I hope you don't have one of those "Cold Air" filer cone on the car?

[Klhumrich]

Stock intake and speedometer works

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