Understanding OBD2

**jasonbernard** · 10-31-2016

Like several others on this forum, I bought a bluetooth ELM327 cheap online, only to find out it won't talk to a 98 Grand Prix GT ECU.

After much searching, come to find out that not all OBD2 protocols are equal.

So, what protocol does a 98 GP use?

This is the page that has helped me out so far : http://scantoolcenter.com/obd2-basic...-your-vehicle/

Looking what pins are actually in the GP, shows our 98 GP GT to be a "SAE J1850 VPW (Variable Pulse Width)"

Going back to the page that I bought my cheapo ELM327 from only says it supports: "ISO14230-4 (KWP2000),ISO15765-4 (CAN),ISO9141-2."

So there you have it - if you buy an OBD2 plug, make sure it supports the OBD2 language/protocol of your vehicle's ECU.

**Explicit_Spade** · 10-31-2016

I think they make universal Bluetooth OBD readers.

The Aeroforce Interceptor gauge is relatively inexpensive and will help you monitor everything you would need to monitor.

**Scottydoggs** · 10-31-2016

either you got a beat elm. or your cigg lighter fuse is blown if it dont light up at all. or if it connected and you didnt load up gm pid's it wont do much either. they do tend to not work sometimes. like its broken.

i got a cheap elm 327 that works just fine on my 98 regal, and every other car or truck ive used it on.

**jasonbernard** · 11-01-2016

In this case, it works in n 09 focus, 11 expedition, but not 98 GP

**ADrugDealer** · 11-01-2016

It's possible his doesn't have VPW on it. Get one that supports VPW or take it apart and post high-res photos of the PCB and i'll let you know what protocols it supports.
Obd is confusing because the standard didn't dictate what protocol is required until 2008 and even then they just said there has to be a CAN network for emissions testing; however, 99% of manufactures just switched to CAN. A modern GM car will have

HSCAN on pins 6/14 of the OBD2 port
MSCAN on pins 3/11 of the OBD2 port
SWCAN on pin 1 of the OBD2Port
Power on pin 16
Ground on 4/5
Possible ALDL on pin 3 (rare but possible)

The only one of those that most people care about is HSCAN because that is what you usually use to scan and what not; however, the other buses carry lots of other potentially useful data.

Older GM Cars tend to have

SWCAN on pin 1
J1850 VPW on pin 2
Power on pin 16
Ground on 4/5

So no, because of the inherent difference between manufactuers, not all ELMs are created equal; however, I will say, the original ELM and any clone *should* support the following

HSCAN
ISO14230-4 (KWP2000)
J1850 VPW
J1850 PWM

**Bronco Boy** · 11-01-2016

Originally Posted by jasonbernard

So there you have it - if you buy an OBD2 plug, make sure it supports the OBD2 language/protocol of your vehicle's ECU.

And/or don't buy cheap online bluetooth stuff. LOL

**Scottydoggs** · 11-01-2016

it seems some have a issue with the mini elm 327. i got the large elm and it works fine for me. it was 11 bucks shipped.

**ADrugDealer** · 11-01-2016

Nothing wrong with the cheap stuff. Works great for the money.

**willie14** · 11-01-2016

I mean I gotta elm 327 mini Bluetooth and mine connects just fine. I had to change some settings around on my torque app as well as buy some connectors to make my tablet Bluetooth capable ( didn't realize that till the last second ) but all in allit works just fine on my 98

**J57ltr** · 11-01-2016

I bought one of the cheap ones from the same vendor as I was recommended and it worked on Acura, Ford, Dodge, Mazda and Nissan but would not work on any GM cars at all. Ended up getting the BAFX one and haven't had a problem since.

**jaydubb71** · 11-02-2016

https://www.amazon.com/BAFX-Products...eywords=elm327

^^^This works PERFECTLY with my 1998 GTP...

**jasonbernard** · 11-04-2016

Here is the cheapo that I know doesn't work:

**willie14** · 11-10-2016

I've got the same one and it works but is not very fast at all. There is major lag in reading real time data. I have a usb adapter as well and yest I was playin around with it and finally got that to connect to my torque pro on the tablet that I use and I gotta tell ya the usb 2.0 cable is super fast with literally minimal to no lag time what so ever. You have to change around some settings in torque pro to accept the cable but it auto connects now and is super fast. I'll post some photos of how I have it ran now and what else I plan to do with it. With anyone using a WiFi or Bluetooth device and want no lag and fast data charting who are using torque pro the usb 2.0 is def the way to go ��

**ADrugDealer** · 11-10-2016

Originally Posted by willie14

I've got the same one and it works but is not very fast at all. There is major lag in reading real time data. I have a usb adapter as well and yest I was playin around with it and finally got that to connect to my torque pro on the tablet that I use and I gotta tell ya the usb 2.0 cable is super fast with literally minimal to no lag time what so ever. You have to change around some settings in torque pro to accept the cable but it auto connects now and is super fast. I'll post some photos of how I have it ran now and what else I plan to do with it. With anyone using a WiFi or Bluetooth device and want no lag and fast data charting who are using torque pro the usb 2.0 is def the way to go ��

Sorry but this is fundamentally wrong.

CAN runs at ~500 kb/s, J1850 runs a 10.4 kb/s. WiFi and Bluetooth have data rates orders of magnitude higher than those (WiFI is nominally around the 250 Mb/s range and BT 2.0/3.0 is anywhere from 50-200 Mb/s) [excluding BT 4.1/2 LE which you are not using anyway] so the lag you are experiencing is coming from a faulty module or **** software.

**Keko** · 11-10-2016

Originally Posted by jaydubb71

https://www.amazon.com/BAFX-Products...eywords=elm327

^^^This works PERFECTLY with my 1998 GTP...

+1 this a good one

**willie14** · 11-10-2016

Well I had the same Bluetooth adapter Jason posted and it worked for my car on torque pro it was just slow/ lag time. I've got better data transfer with the usb 2.0 I bought n had so I'm just gonna continue to use that. I dont need to google what transfers at what rate. This thing might not be as fast as the HP tuner or DHP obdII cable but this works just fine for what I need it to do.

**willie14** · 11-10-2016

Well I had the same Bluetooth adapter Jason posted and it worked for my car on torque pro it was just slow/ lag time. I've got better data transfer with the usb 2.0 I bought n had so I'm just gonna continue to use that. I dont need to google what transfers at what rate. This thing might not be as fast as the HP tuner or DHP obdII cable but this works just fine for what I need it to do.

**J57ltr** · 11-17-2016

How do you quantify this? What is the proof that the USB is "Faster" than a Bluetooth? Data is data and the rate at which it comes out of the PCM is fixed so how do you say anyone thing is faster than the other?

**Bronco Boy** · 11-17-2016

He means the data speed that the Chinese tool can read at. Data transfer speeds are different.....

USB 1.0 data rate, 12mb/s
USB 2.0 data rate, 480mb/s
Bluetooth data rate, 250mb/s

USB is much faster than bluetooth.

**J57ltr** · 11-17-2016

What difference does it make when the PCM only outputs data every 173 ms on average? It doesn't matter if you are using HPT or DHP to scan with you will only get 4-5 scans per second which is 173 ms. Even in the 04+ computers the data only comes out that fast as well. The data transfer rate may be higher but that's like saying your super duper gaming computer is faster at sending data to a printer than a plain Jane run of the mill desktop computer. In that case it doesn't matter how fast the computer is you are still going to have to walk over to the printer to get your copies. Any of the bluetooth devices will still only have the same data sent to them and the logs generated will still be limited by the PCM. While I agree that the transfer rate is faster it's a moot point. I just don't understand rating something as "faster" when it's not the bottleneck.

Jeff