20 replies to this topic

[GaryDoug]

You need an OBD1 cable for your PC scan app? If so, you can buy one for about $50-70 ready-to-use. Or if you have some basic soldering skills and tools, you can make your own cable for less than $20. Here is how...

NOTE - BEFORE YOU GET TOO DEEP INTO THIS POST, TAKE A LOOK AT THE POST LINKED IMMEDIATELY BELOW FOR WHAT IS PROBABLY THE BEST SOLUTION - EASIER AND CHEAPER.

http://www.firebirdn...post__p__888714

Items needed:
1. A USB-to-SerialPort adapter like the Sabrent CB-FT1K, or an equivalent. Just make sure it is a FTDI-based unit, because the Prolific-based ones will not work for this cable. Typical prices are about $20 but you can shop around and find them for about $10 easily.
Here is one: http://www.newegg.co...CFcNa4AodpBwAKA
Install the driver for the adapter by either letting Windows find it or by loading it from the CD supplied with the adapter. In most cases, it is better to run the install utility on the CD before plugging in the adapter.

2. Some parts, which you can get at Radio Shack or any electronics part supply store: a 1K ohm resistor, a diode (silicon or switching types are ok, but NO Zener types!), a DB9 connector (9-pin female/socket type, with solder terminals), two wires at least 6 inches long each. For the wires, stranded AWG20 or 22 would work best. An OBD-1 12-pin plug would be nice, but may be difficult to find cheaply. Leave that for later after you decide it is worth the cost and hassle to find.

3. If the USB adapter you buy has no cable (like the one in the photo), you will need a USB extension cable (about $3 typical online, more $ locally).

4. Some wire, at least two pieces 6" or longer, Different colors are best, or just mark one so you can easily tell them apart later. AWG 20 or 22 would work well at the OBD-1 connector end but may be too large to solder to the DB9. You may want to use two sizes and splice them together for the black one.

Tools needed: soldering iron and solder, wire stripper

Step 1: Fabricate the cable as shown in the photo. Leave the wires as long as you like. Insulate the wires/components at the DB9 connector so they do not short together (ones in photo should be insulated better). "TIN" the ends of the wires that will plug into the OBD-1 connector with solder so that the strands will stay bundled together and not fray. Note the polarity marking on the diode in the photo. The diode's cathode (black band) must be on the end toward the DB9 connector. The resistor is not polarized.

 OBD1-PC cable.jpg   160.05KB   112 downloads

Step 2: Now that you have the wiring done, you will need to re-program the FTDI chip inside the USB-SerialPort adapter. The TXD and RXD pins signals must be inverted for this to work.
Download the FTDI utility "FT_Prog" from the FTDI web site: http://www.ftdichip....ies.htm#FT_Prog

 FT_Prog download.png   71.05KB   70 downloads

Unzip, install, and run FT_Prog. Connect the USB cable on the adapter to a USB socket on the PC. Press the F5 key and you should see your device listed on the left side box. If there is more than one device listed, unplug any other ones you may have. If you see no devices, re-check your installation of the driver for the adapter. Click on "Hardware Specific" and then on "Invert RS232 Signals". You should see something like the screen below but without the checkboxes for any items checked (ON). Now set the "Invert TXD" and "Invert RXD" checkboxes to checked (ON) like shown below.

 FT-Prog Invert signals.png   32.65KB   38 downloads

Once the screen looks like the one above, press the "Ctrl" and the "P" keys together (or click on "Devices" and then "Program"). You should see a box labeled "Program Devices" like below. Click on the "Program" button and wait a few seconds for the message "Finished Programming" at the lower left side of the box.

 FT_Prog program device.png   44.64KB   23 downloads

Close both boxes and exit the program. If for any reason you should change your mind and want to return the adapter to it's original condition, just repeat the above steps, but this time with the two checkboxes unchecked.

You are done. Connect your cable, install and run your scan app. The black wire shown goes to pin A in the OBD-1 connector and the white wire goes to pin M.

Notes: It will cause no damage if you accidentally short the two wires (black and white in the photo) together, but it will stop communications with the PCM while that happens.
This cable is only for the 4th Gen cars and does not have the required resistor for earlier versions, although it could be added and the white wire could be moved to another pin, as required.

[GaryDoug]

A member on another forum suggests mounting the DB9 connector near the DLC, perhaps in the underdash close-out panel with a 2-pin inline connector to allow easy removal of the panel. He wired his into the back of the DLC, then plugs the USB adapter into the DB9 connector.

BTW, if you want to use a 12-pin plug for the DLC instead, you can order one of the cheap Chinese-made 12pin-to-16pin adapters and cut the cable in half. About $5.

[firebird_madness]

Very informative Gary!

I am trying to get my feet wet in the 4th gen computer side of things and seems like a very daunting challenge. A majority of your posts are going to be extremely helpful when I get into this process a little more and I thank you very much for doing this.

[Injuneer]

Very informative Gary!

I am trying to get my feet wet in the 4th gen computer side of things and seems like a very daunting challenge. A majority of your posts are going to be extremely helpful when I get into this process a little more and I thank you very much for doing this.

Just remember, your 2000 is OBD-II.

[firebird_madness]

Just remember, your 2000 is OBD-II.

Thank you for looking out for me Fred.

I also have that 1994 Formula. This will come in very handy when I go to tackle that car.

[GaryDoug]

Some clarifications:

OBD-I is for 1995 and earlier F-series cars. OBD-II is for 1996-2002 F-series cars.


There has been some discussion on other forums about the need to use the FTDI utility to invert the signals. For anything that is advertised an RS232 device (most of them), it will be necessary. For anything that is advertised as a TTL or UART device (somewhat rare), that will not be necessary.
Most devices marketed to the general PC user will be the RS232 type: http://www.amazon.co...sxp_grid_pt_1_0
Most TTL types are marketed to hobbyists in general: http://www.ebay.com/...=item3cbfdfc861

[GaryDoug]

Here is another way to go in the quest for an under $20 OBD1 cable.

1. Buy a "6pin FTDI FT232RL USB to Serial adapter module USB TO TTL RS232 Arduino Cable". Ignore the part that says RS232. This is an error. Cut off the small 6-pin connector; it will not be used. Trim off all wires other than the black, white, and green ones; the others will not be used. Under $10 including shipping.

Here is just one of many sources: http://www.ebay.com/...e-/400356015296

 2nd one I bought sml.png   37.05KB   34 downloads


2. For the 94 only: Buy a "GM 12 Pin To OBD1 OBD2 16 Pin Connector Adapter Car Motor Diagnostic Tool Cable". You will use only the 12-pin part and wires by cutting off the 16-pin connector. The 16-pin connector may not be usable anyway since it has the wrong connections for this use and is sealed in epoxy and not easily changed. It should cost under $8 including shipping.

Here is one of many sources: http://www.ebay.com/...e-/170798772364

 12-pin to 16-pin adapter.png   15.15KB   20 downloads

For the 95 only: Buy a "Universal Male OBD2 16 Pin Connector OBDII EOBD OBD", about $3 with shipping.

Here is one of many sources: http://www.ebay.com/...US:3160&vxp=mtr

 16-pin connector.png   16.8KB   29 downloads

These sources are all in China or Hong Kong and the parts will take 1-2 weeks to arrive.

After cutting off the connectors from the cable(s), connect the two remaining cables/connector together (USB and 12-pin or 16-pin).

For the 12-pin cable (94): The black wire from the USB cable goes to the black wire (pin A) on the 12-pin connector cable part. The green and white wires from the USB cable are to be connected to the brown wire (pin M) on the 12-pin connector cable. The red wire on the 12-pin cable will not be used and may be trimmed short.

For the 16-pin cable (95): The black wire from the USB cable goes to pins 4 and 5 of the 16-pin connector. The green and white wires from the USB cable are to be connected to pin 9 of the 16-pin connector.

Use whatever method you prefer to connect the wires and insulate the connections: solder, shrinkable tubing, tape, wire nuts, barrel crimps, etc.

 OBD1 cable homemade.jpg   81.71KB   53 downloads  OBD1 cable splices.jpg   109.5KB   45 downloads

These converters will not come with any drivers. you must obtain them elsewhere, either from the FTDI web site or from my web file storage location in the same folder as the SCAN9495 app files. This device will probably require the version 24 driver. You can try that one first. If that does not work, try the version 28 driver. After that, you will have to specify which driver to use since you will have two of them on the pc now. The following instructions are for Win 7; yours may be different. Open the Control Panel. Select the Device Manager. Find the USB Serial port device in the Ports section. Double click on it to open it's properties window. Select the Driver tab. Select "Update Driver". Select "Browse my Computer..." Select "Let Me pick from a List...". Select the version you want (28) and click on "Next". Repeat the same exact steps for the "USB Serial Converter" in the "Universal Serial Bus Controllers" section. You will be asked to reboot each time. You should wait until after the second device driver is loaded before you reboot. If prompted to reboot before that, select Cancel.
Unless you are using the latest driver available (28 for now), you may want to set the PC to NOT automatically download the latest driver software, or you may get the newer version by mistake. You can do that this way: Click on the Windows Start icon in the lower left corner of the desktop. In the search box, type "Change Device Installation Settings". Click on the match it finds. In the Device Installation Settings window, select "No, Let me choose what to do" and "Install driver software from Windows Update if it is not found on my computer". Click on "Save Changes".

[GaryDoug]

Here is a diagram that may help explain the differences in the cables.

Attached Files

•  USB-SERIAL.png   75.42KB   70 downloads
•  USB-SERIAL.pdf   14.7KB   126 downloads

Edited by GaryDoug, 21 June 2013 - 01:51 PM.

[firebird_madness]

Very Nice Gary. This will be helpful for so many people. Thank You.

[GaryDoug]

I got a message from someone on another site who said his 12-pin cable pigtail has 4 wires, not 3 as shown in post #8 above. If you buy one of those 12-pin-to-16-pin adapters like above and, after cutting off the 16-pin connector, you see 4 wires (red,black,brown,tan) instead of 3 (red,black,brown), you should use the tan wire in place of the brown wire to connect to to the green and white ones. I have an adapter on order. If it has the 4 wires, I will post a photo.

[GaryDoug]

I got a message from someone on another site who said his 12-pin cable pigtail has 4 wires, not 3 as shown in post #8 above. If you buy one of those 12-pin-to-16-pin adapters like above and, after cutting off the 16-pin connector, you see 4 wires (red,black,brown,tan) instead of 3 (red,black,brown), you should use the tan wire in place of the brown wire to connect to to the green and white ones. I have an adapter on order. If it has the 4 wires, I will post a photo.

I finally received this adapter with the 4 wires. Mine seems to have a yellow wire in place of the tan one the other person reported, or maybe tan looks yellow to me or vice-verse to him. Anyway, I checked the connections, and the yellow (tan?) wire (not red) is the correct one to use for this 1994 connector when you use the 4-wire type adapter. The bottom line is you should check the to see which wire is connected to the M pin and use that one, probably requiring the use of a meter or powered test light (or trial and error). The black wires seem to be consistently connected to pin A (ground).

Attached Files

•  12pin-to-16pin adapter.jpg   99.41KB   17 downloads

[GaryDoug]

I bought another of these cheap (~$3) 12-pin male to 16-pin female adapters. This one has yet another color scheme for the wires. In this one the ground pin A is still black, but the pin M (data) wire is now red. Once again, check these with a battery-powered test light or meter first before using them.

Attached Files

•  OBD1 adapter cable no3.jpg   83.85KB   24 downloads
•  OBD1-2 adapter cable no3.jpg   42.04KB   21 downloads

[79TAFool]

if i make this cable .. and get one of the pc apps? will i be able to see the car information while its running? i have a crossfire injected car that has an intermittent bad stumble or hesitation ... but i need to see if all the sensors are in range when it happens

[GaryDoug]

Does your car have a 12-pin OBD1 connector? I am not too familiar with anything before 1993. Maybe some of the other guys here can help.

Edited by GaryDoug, 04 October 2013 - 08:16 PM.

[MONARCH455]

I know this is a old thread but have a question.

Will the homemade cable from the original poster work on a 1987 Buick Lesabre Custom 3.8 multiport injection?

Not sure what ecm is in it. I do know I do not have a pin M. I have pin A,B,E,F,H. This is a 12 pin ODB1 connector.

From what I can tell I would only use pin A, E.

Thanks

Greg

Edited by MONARCH455, 13 July 2014 - 02:05 PM.

[GaryDoug]

I am not sure. You would use pin A as the ground and pin E as the data. Is there a wire on pin B? If so you may have to add a resistor to pins A and B.

[Yesterday]

Thank you for this guide, Gary. I had fun making the cable and testing it. Currently, my Service Engine Soon light is on. Where in your software does the code that trips that light show up? When I scanned for everything, I found that all of the sections said something along the lines of "no codes found." The other thing is that when I replay a file that scanned for everything (engine, transmission, electrical, abs, etc.) it only replays the engine data. Again, thank you for your very cool instructions and software!

Edited by Yesterday, 05 October 2014 - 06:05 AM.

[GaryDoug]

The powertrain DTC information is read from the Engine and Transmission scans. There is some overlap, but running both should deliver all trouble codes. Make sure you are running the app from the same folder (not zip file) with the "malf.csv" file. That file has the DTC mapping.

At present, only the engine data and DTC summary is stored in the datalog file, regardless of whether any other sections are enabled or not.

[Yesterday]

Thanks for the reply Gary, I'll take another look at it later this week. I wonder what might consistently turn the SES light on but not throw a code?

[GaryDoug]

It has been discovered that the manufacturer of the serial port adapter chips (FTDI) had implemented a "kill" function to their latest chip driver update. The result is that any counterfeit chip that receives the normal updated driver will be reprogrammed to NOT work correctly and then Windows fails to load the required drivers. This started about two weeks ago. The problematic driver has been removed from the Microsoft Windows Update site as of a few days ago, but FTDI intends to reinstate some kind of method to not allow the chips to work. It is almost impossible to tell whether you have the counterfeit chip or not since both the Chinese-made fakes and the really legit ones are both made in China.

If you have experienced problems with either the OBD1 or OBD2 adapters in the last week or two, it may be due to this update. Unfortunately at this time, there is no easy fix; but attempts are being made to find some. There are some workarounds however, so stay tuned here.

For users that have NOT yet installed the cables, do this: Download and install driver version 24 or 28 from my web site file storage area that has the OBD1 and OBD2 apps. Switch off network access (unplug network cable or turn off wifi). Plug in the adapter cable and let the driver install to version 24 or 28. Then turn off automatic driver updates (check back here for the procedure or see the last entry in the first post about the "..under $20 cables")
http://www.firebirdn...714#entry888714

Fixes:
https://www.youtube....h?v=RZH_qGautqM

https://www.youtube....h?v=SPdSKT6KdF8

Edited by GaryDoug, 28 October 2014 - 02:35 PM.