need help
 

I have built a cable for my car and it will link up with the car on but not running but it will not link up while the car is running I tried rebuilding the cable with no luck. It has worked many times before so I don't know what to try next. any help would be greatly appreciated.


thanks

almost forgot I am using tunerpro for my datalogging

Can you post a schematic or a link to the one you used?

I used the 2 transistor cable off of your site

when you say it will link up (key on, engine off), have you confirmed this by pressing the gas pedal and watching the TPS voltage reading?

8192 or 160 baud?


It seems a little strange that things would fail once the engine is running.

I have seen the tps voltage change when hitting the gas pedal but as soon as the car starts all of the readings stop. It is 8192 baud. I will check all of my solder connections tonight and make sure that they are all good and see if that helps anything.

If all your solder joints check out, it may be a noise issue. Not sure what could cause it, but sometimes its a faulty or failing plug wire, plug, ignition, etc. Other times it could just be a ground wire rubbing on a moving part, etc.

The MAX232 circuit is much more robust.

I re soldered all of my connections and still the same thing. But then all of a sudden everything started working correctly. so I am guessing that I have a bad ground wire. Now for the fun part, finding where it is.

I think I found a short in my ac system if i turn the ac on the computer will link up perfectly but as soon as I turn the ac off it quits reading data. so I tried unplugging the ac switch to see if that would help and it does read but it is in and out really bad. I also noticed that when I turn the ac on my volt gauge goes up, is this normal or do you think I may have an alternator problem.