A few posts back we took a look at the diagnostic plugs. What I didn’t cover last time, was what the function of Vf. So that’s what we’ll cover this time around.
The late model connection is very easy to find.
The early model cars, it’s the #3 pin as shown in the above pic.
But what is the Vf? From what I gather on the internet. It’s a voltage output for dealer techs, or anyone with knowledge and a digital multimeter to diagnose issues with the cars tuning.
A digital meter is required so head out to harbor freight and grab one for free with one of them newspaper coupons. You can tap into the Vf signal from the diagnostic plugs. I found it more convenient to run it from inside the car. Reference the vehicle ecu harness plug diagram for reference. Google is your friend.
Once the car is up and running, it’ll take a few minutes to get the oxygen sensor warmed up to start get readings. Once running the digital meter will be sending voltage outputs from the ECU. You should be reading between 0-5 volts. Voltages close to zero, the engine is running rich, closer to 5V then it’s running lean. But don’t use this as an optional wideband sensor. This ecu output occurs after the ecu has taken a couple of oxygen sensor samples.
Best is to take the car out for a drive while a co pilot notes down the voltage outputs readings while cruising. Preferably on the freeway since that’s where most will drive and require and optimal mixture. Once you have a rough idea where the engine is running, you may or may not need changes. For the more extreme cases, modifying the AFM may be required to achieve the reading of 2.5V. To modify the AFM please refer our friend Google. As for the gray goose, it’s close enough and will be left alone. Though I may try to lean it out a put more to try and gain some extra miles. Definitely a good tool to have for fine tuning.
Posts
1 comment:
I never knew this! Cool!
Post a Comment