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94 olds obd1 w/obd2 connection


yarslew's Avatar
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05-01-04, 09:41 AM   #1  
94 olds obd1 w/obd2 connection

I have a 94 olds regency with 3.8 engine. Sticker under hood says obd1. Connector is 16 pin obd2 style. One online source says to bridge 5&6 to get code reading, but I have no wire in #6. Dealer service dept. says I have to have an adapter and use an OBD2 scanner. I have the scanner, but no adapter...and he sounded a little unsure. Is there a way to read the codes without using a scanner? If not, what is a source on an adapter?

 
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05-01-04, 11:44 AM   #2  
If you have an OBD2 connector the codes must be read with a scan tool.What the dealer probably meant was you need a Tech 1 scan tool with an OBD2 adaptor or an OBD2 scan tool.1994/1995 are the only years this applies to.Earlier models you could jumper a to b and check codes.1996 and up is strictly OBD2 brought to you by the EPA.

 
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05-01-04, 06:38 PM   #3  
Thanks for the reply. So, you are saying I should be able to get codes with my Code Reader...which is an Equus 3100? I had just assumed it would not work since the system is an OBD1. And I did not want to attempt to get codes, and then not be able to trust whatever it says.

 
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05-01-04, 06:59 PM   #4  
It should be able to extract and read the codes but it may not have the definitions for codes that are not "PO" codes.

 
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05-01-04, 07:14 PM   #5  
I just tried the Equus 3100 on it, and all I get is a "Err" message. When I hook it up, it turns the scanner on, but when I press the "Link" and it goes into "Read" mode, all it comes up with is "Err." Since this is an OBDII tool, maybe I need an OBDI scanner with an adapter or whatever that will fit the 16 pin connector? I'm getting nowhere. My "Check Engine" light is on constantly...not intermittent, so it should show a code if it's going to.

 
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05-02-04, 04:20 AM   #6  
It looks like you might be out of luck. I'm not familiar with the code reader your referring to but by the way it is acting, it's only has one mode in it, "OBDII Generic". Most of our scanners have specific modes for every make of car plus generic. It looks like yours only has generic. That's the difference between a couple hundred dollar code reader and a couple thousand dollar scanner.

 
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05-02-04, 05:20 AM   #7  
You are probably right. It does say it is OBDII scanner for 1996 and newer cards. It lists manufacturer codes in addition to generic codes, but probably just doesn't communicate with my OBDI. Guess I'll have to go to Plan B, as soon as I have a Plan B.

 
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05-02-04, 05:59 AM   #8  
Call around and ask how much to have the codes read then post back here with the code #s

 
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05-06-04, 02:44 PM   #9  
Ok. I found a friend who I had loaned my laptop to had an Auto XRay with the cable for 94-95 Gm cars, so we swapped favors. The trouble code is PO122...throttle position sensor, low circuit input. That's what I had suspected since there is no downshift. Now the trick is to find it and find if the problem is there or up the line from it. Is there a path/chart for that?

 
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05-06-04, 06:14 PM   #10  
It's a pretty basic test with a DVOM. Just read the key on voltage at the signal return wire and slowly sweep the entire throttle span and watch for smooth increases in voltage with no dropouts or glitches. Should be between .5 and .9 at idle increasing to 4.50 to 5.00 at WOT.

 
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05-07-04, 03:55 PM   #11  
Problem solved. Throttle Position Sensor was bad and was replaced for $50 from auto parts store ($52 at dealer). I'll go ahead and post my checking of it in case anyone else is looking for answers.

The Auto Xray scanner, using the blue cable because this is a 94 model with OBDI with the new OBDII connector, showed PO122 Throttle Position Sensor low input. When I began to check the sensor, I began by checking to see if there was voltage from the computer. With the key on, there was supposed to be 5 volts coming to the TPS from the computer on one wire of the 3 wire connector. On this vehicle that was the wire on the left in the 3 wire connector, looking at it from the front of the vehicle. Voltage was measured putting the red lead of the digital volt meter on that wire, and the black (-) lead on the wire on the opposite side (right) of the connector, which I believe is the ground. Voltage was correct here. I was a bit concerned about that since I had installed a new battery and had not known the ignition was turned on, and that can do damage.

With the connector in place, I inserted pins into the back of the connector to contact the wiring inside the insulation on the middle wire and the wire on the right (ground). I touched the red lead of the volt meter to the middle wire and the black lead of the volt meter to the pin and wire on the right and got zero voltage. I had a helper push the accelerator all the way down, and should have received almost five volts at wide open, but still nothing. I then turned off the ignition, removed the wire connector from the TPS, switched the DVOM meter to Ohms, and checked for continuity on the TPS between the TPS terminal on the left (which connects to the wire from the computer) and the TPS terminal in the middle (which sends a varying reduced voltage back to the computer). There was no continuity. This was double checking, but I knew beyond a doubt the TPS was bad. When I bought the new TPS, there was continuity between these two terminals, varying as the throttle is moved to wide open.

Replacing it on this car entailed removing the aluminum plenum which houses the MAF so I could access the two screws to remove the TPS. This plenum connects to the PLASTIC (dumb idea) intake manifold. These are held together with three sex nuts in the plastic, a stud into each sex nut, and regular nuts against the aluminum housing. (Sex bolts/nuts are what we call them in construction: a bolt or screw that goes into a threaded cylinder that serves as a nut. The cylinder then fits tightly into a hole, like the manifold in this case). The sex nut in the plastic manifold housing has tiny splines which are supposed to keep it from turning---but they won't. Get a wrench on it and hold it while removing the nuts. This won't be easy because the head of the sex nut is about 1/16 inch thick. GM says the sex nuts are a part of the intake manifold..can't buy them separate. One of mine was so frozen I had to grind the nut and stud off, and replace with a bolt through from the front with a nut on the back. It's not ideal, but it works.

Bottom line. Turned on the key and no "check engine" light. Life is good.

 
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