My ECU readings are:

Short Term Fuel Trim B2 -7%

when I got error code P 0103 "Mass or Volume Air Flow Circuit High Input"


The MAF has been replaced and it still happens.


Any ideas?

 

STFT is the ecus way of making small quick changes to the injector pulse width or Ti time in the mid and upper ranges of the engine. It adds or subtracts fuel to keep the engine at Lamda (14.7 to 1 air to fuel ratio). It will add or subtract untill it hits it's limit- at that time this causes the long term fuel trim to increase or decrease one range which is a larger adjustment. At that time the stft starts over making it's minute adjustments until the system is at idel or it needs to bump the ltft up or down again. If the ltft reaches it's stop where it can't add or subtract any more fuel to stay at lamda it will stop making adjustments based on the o2 sensors and go to a default map working in conjunction with your other sensors.
Your code could have indicated a bad MAF probably there's an air leak somewhere between the air intake and the engine (boost or diverter hose maybe), a seriously dirty air filter, a gummed up throttle body or a wiring prob between the maf and ecu.

 

Oh, also though rare on a fairly new car, there could be a backpressure prob in the exhaust/ cat converter.
BTW, when the maf was installed, are you certain the hoses were back on and seated properly- could be an air leak there. Seth.

 

Seth,

Thank you for your help.

So an ECU freeze frame reading of "Short Term Fuel Trim -7%" means that the ECU pulled 7% of fuel?

Would this mean that the ECU mapping is too rich?

The code: P 0103 "Mass or Volume Air Flow Circuit High Input"
would indicate the opposite.

It would indicate too much air not too much fuel. Am I not understanding this right?

Thank You.

 

I believe you have a lean running condition under boost or moderate load but i'm not sure i interpret your data correctly. If that -7 is stft ADAPTATION VALUE, then that would be a richer running condition but the code mostly points to a lean running condition or a wiring/voltage issue between the MAF and motronic ecu. If the car were in my shop i would just start with a diagnostic smoke test and then use the PST2 and a break out box if the smoke test comes up null to diagnose a possible electrical issue. Seth.