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View Full Version : Location of OBDII port on LT-1?


frosty
01-24-2011, 11:07 AM
Hello all,

I finally got a scan tool, and cannot find the OBDII port to plug it in to! :confused:

1998 LT-1 330hp in a 1998 Maristar 225.

Nothing wrong with engine, just want to play with the scan tool.

Does anyone know where the port is located?

Have been pulling all the connectors on the engine I could find, and I could not find one that fits the OBDII dongle.

Thanks!

David

gotta_ski
01-24-2011, 01:09 PM
From what I've read and from looking over my own 98' LT-1, I don't think it has an OBD II port. I believe our motors use MEFI, Marine Electronic Fuel Injection, which has a different plug. I'm not sure if MEFI is a GM creation or an Indmar creation for that matter.

flipper
01-24-2011, 01:11 PM
There is no OBDII plug on it.

FrankSchwab
01-24-2011, 07:24 PM
I had the same plan when I got my boat, frosty. And I got the same answers - there's a port, but it's not an OBD-II port.

Table Rocker
01-24-2011, 08:23 PM
There are some MEFI systems that aren't too outrageous in price.

http://www.obd2allinone.com/sc/details.asp?item=mefiscan1

ahhudgins
01-24-2011, 08:38 PM
There are some MEFI systems that aren't too outrageous in price.

http://www.obd2allinone.com/sc/details.asp?item=mefiscan1


I'm glad you posted that link. I bought one of the code readers for my 95 MEFI just to read a code if one ever comes up and I modified it to install a "check engine" led on my dash. I've been bidding on some scan tools that show up on ebay from time to time but this looks more like what I'm looking for at a cheaper price. I just want to know what my ECM shows as the engine temperature.

JimN
01-24-2011, 09:29 PM
Please delete. Thank you.

JimN
01-24-2011, 09:30 PM
It's not OBD II, it's OBD I and the '98 used the MEFI 2 controller, possibly CEFI 3.

frosty
01-24-2011, 10:08 PM
Thanks for the replies, guys.

So, if I get this correctly, I can either purchase the CodeMate code reader for $39 (http://www.rinda.com/marine/marine.htm#merctool), and read the LED flashes to get the MEFI error code (but not know the exact component that triggered the code),
or spring for the USB -> MEFI cable for $195 (http://www.obd2allinone.com/sc/details.asp?item=mefiscan1) and use the free software (http://www.tunerpro.net/downloadApp.htm) to read the error codes, and much more.

Am I missing anything?

It doesn't look possible to build your own MEFI cable, must be some circuitry involved.

Thanks for the education!

JimN
01-24-2011, 10:52 PM
Thanks for the replies, guys.

So, if I get this correctly, I can either purchase the CodeMate code reader for $39 (http://www.rinda.com/marine/marine.htm#merctool), and read the LED flashes to get the MEFI error code (but not know the exact component that triggered the code),
or spring for the USB -> MEFI cable for $195 (http://www.obd2allinone.com/sc/details.asp?item=mefiscan1) and use the free software (http://www.tunerpro.net/downloadApp.htm) to read the error codes, and much more.

Am I missing anything?

It doesn't look possible to build your own MEFI cable, must be some circuitry involved.

Thanks for the education!

The codes tell which sensor is reading the information. It's not an elaborate system- each sensor that can cause a code will either report higher or lower voltage than normal. The knock sensor either hears knock or nothing- either will cause a code to be stored. The IC (Ignition Control) Module will also cause codes to be stored. The codes have been posted here several times and they're the same ones GM has used for decades.

To read the codes on the MIL (Malfunction Indicator Lamp), you need to connect terminals A and B on the DLC (Data Link Connector), which is sometimes called the ALDL (Assembly Line Data Link). If you don't use the MIL, you can use a test light on two of the other DLC terminals. You won't see actual voltages or percentages with a scan tool.

I wouldn't recommend changing any of the values in the calibration program, if the software allows it. Changing the tuning can result in catastrophic failure if you try to guess.

ahhudgins
01-25-2011, 12:01 AM
Thanks for the replies, guys.

So, if I get this correctly, I can either purchase the CodeMate code reader for $39 (http://www.rinda.com/marine/marine.htm#merctool), and read the LED flashes to get the MEFI error code (but not know the exact component that triggered the code),
or spring for the USB -> MEFI cable for $195 (http://www.obd2allinone.com/sc/details.asp?item=mefiscan1) and use the free software (http://www.tunerpro.net/downloadApp.htm) to read the error codes, and much more.

Am I missing anything?

It doesn't look possible to build your own MEFI cable, must be some circuitry involved.

Thanks for the education!

The codemate is the one I bought and modified. The only thing in a codemate is a switch to put the ECM in service mode and a led with a resitor. I mounted my led in the dash so it functions as a check engine light in the normal mode. The way I read it (I'm going to call and check) the $195 is for the cable and the "monitor" software. It doesn't allow any changes to be made as Jim mentioned. The tunerpro appears to be the full blown software for messing up your ECM so it won't run any more!;);)

ahhudgins
01-25-2011, 12:06 AM
The codemate is a quick, cheap way to check for a trouble code. This link will also show you the connector.
http://www.mastercraft.com/teamtalk/showthread.php?t=36502&highlight=quick+project

frosty
01-25-2011, 01:02 AM
Jim,

Thanks for the replies, and explanation!

It's not OBD II, it's OBD I and the '98 used the MEFI 2 controller, possibly CEFI 3.

Still more to learn! OBD I is the type of connector, and I am looking for a 12 pin connector that looks like this, correct?

http://www.obd2allinone.com/uploads/carconnector.jpg

Any idea where this DLC would be located? Mounted to the engine somewhere, or is it one of the multiple capped, loose, wire harness terminations, like the fuel pump relays?

To connect to the OBD I port, would this work?
http://www.obd2allinone.com/uploads/aldlusbbig.jpg for $59 (here (http://www.obd2allinone.com/sc/toplevel.asp?cat=2))

I did check the model # of my MEFI, which in this case ('98 LT1) turns out to be MEFI-2.


I wouldn't recommend changing any of the values in the calibration program, if the software allows it. Changing the tuning can result in catastrophic failure if you try to guess.

I would like to be able to read temps, hours ran, etc., and read any error codes should they appear...no reprogramming for me, thank you!
More curious at this point, but I can justify it to myself if I can use it to diagnose a problem if it occurs...:rolleyes:

There is also something called an "EFI Diagnostic Adapter" here: http://www.rinda.com/acro/prodlist.pdf
At the bottom of page one, just above the above mentioned CodeMate blinky, is a "#94005 GM-Delphi MEFI 1 - MEFI 4b EFI Diagnostic Adapter" dongle for $39, would this do the same thing as the $59 one above?

JimN
01-25-2011, 09:45 AM
Still more to learn! OBD I is the type of connector, and I am looking for a 12 pin connector that looks like this, correct?

Any idea where this DLC would be located? Mounted to the engine somewhere, or is it one of the multiple capped, loose, wire harness terminations, like the fuel pump relays?

To connect to the OBD I port, would this work?
http://www.obd2allinone.com/uploads/aldlusbbig.jpg for $59 (here (http://www.obd2allinone.com/sc/toplevel.asp?cat=2))

I did check the model # of my MEFI, which in this case ('98 LT1) turns out to be MEFI-2.

I would like to be able to read temps, hours ran, etc., and read any error codes should they appear...no reprogramming for me, thank you!
More curious at this point, but I can justify it to myself if I can use it to diagnose a problem if it occurs...:rolleyes:

There is also something called an "EFI Diagnostic Adapter" here: http://www.rinda.com/acro/prodlist.pdf
At the bottom of page one, just above the above mentioned CodeMate blinky, is a "#94005 GM-Delphi MEFI 1 - MEFI 4b EFI Diagnostic Adapter" dongle for $39, would this do the same thing as the $59 one above?

OBD I is the system, not the connector and while your adapter may work, that's not the same connector used in marine applications. Yours is at the rear of the motor and has a black cover, possibly with some gray on it. It should be near the circuit breaker and it's easier to get at it if you release the gas struts on the motor cover from the brackets on the floor.

The cheap code reader will show only the codes, not actual data. Showing only codes is fine if you need to diagnose a problem but the data lets you see if something is out of range, although you'll need to find out what the correct range is, in order for that info to do any good. For example, the TPS will indicate a voltage and a percentage- if the throttle position indicated is 2% and you're at WOT, it means the TPS is either the wrong part, or it's defective. The reason I mention this part specifically is because your motor won't work with the TPS from most of the rest of the GM engine lineup.

frosty
01-25-2011, 06:53 PM
OBD I is the system, not the connector and while your adapter may work, that's not the same connector used in marine applications. Yours is at the rear of the motor and has a black cover, possibly with some gray on it. It should be near the circuit breaker and it's easier to get at it if you release the gas struts on the motor cover from the brackets on the floor.

Thanks for clarifying that for me, I will dig around & look for the connector next month when I get some quality time with it!