Just watched the latest ep of Know How, saw you were talking about OBD2

[G+_Taylor Graham]

Just watched the latest ep of Know How, saw you were talking about OBD2. Didja know about the ELM327 mini OBD2 bluetooth adapters? You can monitor anything your OBD2 port has access to with any android/iOS device. You can even take video on the device and overlay info/gauges/maps using an app called Torque. I have one, its great. Have diagnosed, fixed, and cleared a few engine codes already.

[G+_stephen delaney]

and you can get one for $7.99 on newfrog.com right now

[G+_P Costello]

Love the Torque Pro (or Free for that matter).

 

https://play.google.com/store/apps/details?id=org.prowl.torque

[G+_Ben Reese]

Wow. I had never heard of newfrog, so thank you for the introduction. I agree that an ELM327 bluetooth adapter is the way to go. Pair that to an Android phone/tablet and run the Torque app.

[G+_Daniel Armstrong]

Couple problems, there are several versions of the ELM327 clones, some work, some don't. For instance there are 2 versions just of the translucent blue one pictured, one with a solid bump on the connector side, and one with a separate tab there. I got the one with the tab and it worked on '90s GM, and Chrysler stuff, but wouldn't connect to an '05 Impala.

 

2nd, iOS doesn't allow Bluetooth SPP (serial port protocol) and the adapters are OBDII to serial bridges with either a serial-bluetooth, serial-USB, or serial-WiFi bridge, so you can't use the Bluetooth version on iOS.

 

So while the clones are nice, a genuine ELM327 would be better, and if you really care a service shop level tool like the OTC 4000 Enhanced, Genisys or Pegisys are nice to have, but I like Torque Pro or OBD Car Doctor better.

[G+_Daniel Armstrong]

Oh and if you are going to do OBDII please watch some YouTube videos from ScannerDanner and the like about what the data you are getting means, in particular how important long and short term fuel trim numbers are.

[G+_Ben Reese]

Yeah, I always wondered what Fuel Trim meant. I'll have to look it up... The other thing I'd like to learn is how to pull other codes using these things. I think the timing might be slightly off on my diesel bug, but I can't tell without pulling the right codes.

[G+_Ben Reese]

I also agree about the cheap ELM327 adapters... I've purchased 2 of the cheap ones and have been lucky on their compatibility, but they have both had the same generic MAC ID.

[G+_Daniel Armstrong]

Fuel trim is a correction value table on top of a fixed table programmed at the factory by the design engineers. They run each pre-production vehicle on a dyno and record how much fuel is required for each condition, IE X RPM and Y load = Z injector pulse width.

 

Since nothing is perfect, this factory table can't be used as-is, so the trim tables tweak it on the fly, for instance just using E10 fuel which has ~3.3% less energy per unit volume will increase the LTFT by a corresponding ~3.3% across the board.

 

So:

 

Positive trims across the board= low fuel pressure or low fuel BTU content.

 

Negative trims across the board= high fuel pressure.

 

Positive trim at idle but normal under load=vacuum leak

 

Negative trim at idle but normal under load= vacuum line off fuel pressure regulator or un-metered fuel, (leaky injector or leaking fuel pressure regulator diaphragm).

 

Normal at idle but positive under load= plugged fuel filter.

 

Etc.

 

The fun part is that without checking these trim numbers your car can have a problem and you wouldn't ever know it because it is so good at compensating for it. The long term trim typically has to be off plus or minus more than 20% before a code is set and the MIL comes on.