GM, OBD1 (sometimes called 1.5) question,

[Big Wave D]

Trying to fix a no start/run problem with a 1994 Oldsmobile 98 Regency. The car is naturally aspirated 3.8L engine.

My problem is this:

'Borrowed' a $400 code reader from an automotive store's "Loan It" program. The scanner is touted as OBD1&2 w/CAN and ABS.

Problem is that car is OBD1 computer equipped but the connection under dash is the OBD2 style. When using the OBD2 'ended' cable for 'proper' connection to car's port, this is what happens:

I turn key to On, Scanner fires up and says hit Link button, I press the Link button and see that unit is cycling through several protocols, but no connection is every made. Finally, it stops trying to connect and screen says "Unable to Establish Connection".

Can I make up some type of homemade harness to use with Square OBD1 adapter, so that I can tap into the proper pinout of OBD2 connector on car?

If so, I'd need some instructions on which numbered pin from OBD2 car connector goes to which Letter 'numbered' pin on Scanner cord pinout.

I've read enough off of Internet to know that jumping pins is a definite No No. Frying of the ECU is real possibility.

Does anyone know what Code Reader/Scanner is out there that is compatible out of the box with this type of system?

Thanks to any and all who can help shed some light on this matter.

 

[JakeBrake]

I found this site to be very useful for troubleshooting my 95 GMC.

GM 1983-1995 OBD1 Decoder

 

[Big Wave D]

Thanks for the website, but I fear that I am not able to do the jumper routine.

I don't have the square connector and its accompanying pin layout. My connector is the OBD2 style.

I've wondered if it was possible to physically re-pin the connector. What I don't know is if the pin leads for the obd2 cable go to the same pins on the scanner as the cable used for the obd1 adapter.

Don't want to own a so-far, worthless, scanner because I fried something with it internally.

 

[Big Wave D]

Maybe this site will help:

AutoXrayｮ

I can't try it this evening, but it certainly sounds promising.

Thank you very much!

 

[David-Davies]

Hello Big Wave D. If you give me the first half of the serial number, I'll use my Snap On scaner to let you know what yopu have. I wouldn't fufaw around with jumper wires, you could hurt some thing really bad. I geuss that your engine turns over, but won't start. Proably doesn't have a distruibitor. First check for spark. [plug wire]. If spark ,check the crank sensor, and the canshaft sensor. Could be fuel. When you turn the key to on. Do you hear the fuel pump, rum, and do you hear a click that makes the fuel pump run. Disconect a fuel line, put the end in a contaner, have some one turn the key on. Have you Got fuel??? You have to check for fuel pressure. [$15 air pressure gage]

David-Davies

 

[Big Wave D]

Jumper wires worked. I wasn't crossing any terminals to try and get a dummy light to flash codes.

Used the GM OBD1 adapter and used jumper wires to 'connect' to proper pins on the cars OBD2 connector.

Here's the weird part. Scanner asks for Year and 8th digit, like it's supposed too, then I hit the Link button, connects right up, says something about code read successful, then I get to the codes page. Nothing, no DTC's set. I tried multiple times. Disconnected the scanner, turned car over, then reconnected scanner, turn ignition switch on and off. Zilch, nothing, nada, zero, empty, clear,...

Half to have some help tonight so someone can turn the car over while I go about checking spark, fuel, etc.

As a side note, it almost sounded like it was going to catch and run once, while I was just cranking the motor in hopes of setting some kind of DTC code.

So, my saga continues...

 

[David-Davies]

If you don't have any trouble codes, then the problem isn't computer controled. Spray a little shot of starting fluid in the air cleaner. If it's a fuel problem, it will fire.
Dave

 

[Big Wave D]

If you don't have any trouble codes, then the problem isn't computer controlled. Spray a little shot of starting fluid in the air cleaner. If it's a fuel problem, it will fire.
Dave

I didn't have any at the time of the former posts.

You are correct. I bought some starter fluid and it did run momentarily.

Do you know if this car has a fuel pump prime lead and where it might be located in the engine compartment.

Trying to see if pump is bad or if there is a problem with wiring or relay.

Thanks for your help.

 

[automech]

check for prime lead in relay center, if it has one it is a red wire near the fuel pump relay. I personally would check the fuse first ( should be fuse 6). If the fuse is good go straigt to the relay and see if you hear it/feel it click when the key is cylcled. The pcm controls the power to the relay coil for pump prime. Run power to the pump comes through the oil pressure switch, bypassing the relay. After quick checks at the relay I would go down to the pump connector in front of the tank to check voltage/ground there. Grey is supply, black ground. One quick test to try is banging on the fuel tank while a helper cranks the engine. I use a rubber mallet. This jogs the pump motor into life. If the car starts now, you know the pump is bad. Hope this helps good luck

 

[Car Doc]

According to my Modis both the 12 pin OBD1 and the 16 pin OBD2 ALDL are supposed to be there under the dash on the left.

My scanner would probably communicate on either protocol at least it says it will so maybe you need a better scan tool or find the 12 pin taped to the harness under there somewhere and that's what I would be looking for.

94 was very early in the OBD2 change over it wasn't mandated to be working until 96 and only the high end cars had it actually working in 94-95 so I doubt if the car is actually OBD2.

The wiring may be but doubtful the ecu is and therefore I don't see the scanner communicating on OBD2 protocol if that's the case.

Even if its got a rear o2 it still may not be OBD2 fwtw I have seen it like I said the wiring may well be OBD2 but not the ecu.

So the factory may have used the 16 pin for their uses but I wouldn't count on just every scan tool to have included the software to communicate with these very early ones. my 2c

Actually fwtw I wouldn't even need a scan tool to figure out why it wont run it wouldn't even come out of my tool box for that problem now after I had it running I would if the mil was on but not for a no-start.

I would hook a fuel pres gage up put a noid light on and install a spark tester and do a compression test and I would go from there see whats out of whack and follow that trail diagnosis 101. A good ohm meter and a wiring diagram and a pin voltage chart is my main diagnostic tools. hth