so after I loaded a new tune to my PCM, the car would start for a second, and then die. W/B read full lean. we assumed the tune was too lean so we went to load another tune and.. cannot communicate!

the diagnostic port will not work, and the fuel pump will only prime for a split second. I bypass'd the fuel pumps relay and the car ran fine which leads me to think the anti theft system is making the fuel pump not work, but the starter does? and i'm not sure how thats linked to the diagnostic port not working but..

i did notice a burnt wire in the pcm wiring but fixed it and no change. anyone have any idea?!

 

is there any way to program the PCM without the diagnostic port?

 

Looks like a messed up PCM.. Normally the PCM picks FP relay for 2 seconds when key goes from off to on and then PCM picks and holds FP relay on when it sees OPTI pulses (engine is running). Security (or VATs) will kill the injector pick during startup, not the FP relay. If the FP pick line from the PCM is not present when you start it up, and the ALDL link will not work then the code or PCM is messed up. A messed up PCM can be fixed by sending it to a mail order shop, BUT since you had a burnt wire there may be some other physical damage. May be able to get one at a junk yard for $50-75.00 make sure it's from an M6 not and A4 and insure the code you load it up with is good.

 

Why wouldn't the wideband read lean? the engine isn't running, o2 sensor is heated up, and it's reading the oxygen rich atmosphere.

 

just made a home setup to test the PCM with another wiring harness in my room and it still won't connect so i'm going to go with fried PCM too. this is my 3rd one sadly.

 

Hate to say it but PCM failures are pretty rare. People that do a lot of tuning carry extra's because of laptop/cable/software failures during a code load messing up the PCM internal bios code. But the PCM normally does not just go, third one seems like you are having other problems.

 

the other ones were my own fault, unfortunately. laptop battery read 50% and went to 2% on tune. died. 1 pcm. tunercat had an update so i updated.. but a few days later they revealed the new update could cause a checksum error. which it did, and killed another. this time the wires got burnt mid tune i assuming and once again, owned it.

bought a socketed PCM, and have an eprom burner so we'll see if i can avoid this from now one haha.