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Old 06-05-2005, 07:48 AM
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Reading OBD I codes with a multimeter

I have a 1984 Chevy Caprice Classic with OBD I in it. I've heard you can read the trouble codes with a multimeter for OBD I systems but I don't know how. So the question is, How do you?

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Old 06-05-2005, 11:40 AM
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I don't have my manuals at hand,but you should be able to retrieve codes by putting a jumper wire between two terminals in the data port located under dash on drivers side of car.Installing this jumper and cycling ignition on and off in a specific sequence will cause check engine light to blink out codes.
I know my haynes manual has all the specific info to do this,as well as what each code signifies.
After you retrieve whatever codes are stored,you will need a multimeter to check various components,such as o2 sensors,tps,temp and map sensors.
I have seen codes mean different things on different models and years of cars,so I would recommend you buy the proper manual for the car you are working on.
One other note-codes can be set by wiring problems such as poor connections,shorts to ground,poor component grounds,etc,so plan to check entire sensor circuit to find source of problem.For example,you may get a code for an o2 sensor-Iwould first check sensor with multimeter, as per manual,before I bought a new sensor.Most parts stores won't let you return
electrical or electronic parts after you have walked out their door.
HTH,George
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Old 06-05-2005, 01:55 PM
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Quote:
Originally Posted by Fast Orange
I don't have my manuals at hand,but you should be able to retrieve codes by putting a jumper wire between two terminals in the data port located under dash on drivers side of car.Installing this jumper and cycling ignition on and off in a specific sequence will cause check engine light to blink out codes.
I've heard of inserting a multimeter (non-digital) into the data port, and then watching the sweep to determine the codes.

Quote:
Originally Posted by Fast Orange
I have seen codes mean different things on different models and years of cars,so I would recommend you buy the proper manual for the car you are working on.
I have the GM shop manual for this vehicle and it lists all the codes.

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Originally Posted by Fast Orange
One other note-codes can be set by wiring problems such as poor connections,shorts to ground,poor component grounds,etc,so plan to check entire sensor circuit to find source of problem.
That's exactly what I will be looking for. I just rebuilt this engine and am currently working on wiring it. I've left off a couple components, ie. AIR system and EGR, and I will want to be able to see what codes I get when I fire this bad boy up.
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Old 06-05-2005, 05:31 PM
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kringold,
I am not sure what auto chains you have in WA, but in AZ: Autozone and Checker will loan you, ODB testers. Just leave a CC imprint and take it home. When you bring it back they credit you CC.
Bob
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Old 06-05-2005, 06:19 PM
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I have Autozone, which I called and they don't even have an OBD I scanner, and I have Schuck's (Checker), and I know they don't loan tools without a charge. I do have a multimeter. Geez something as old school as this, you'd think someone would know.
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Old 06-05-2005, 06:21 PM
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I havent heard of a way to actually read codes from the data port with a multimeter,but I don't have a lot of experience or background in OBDI systems.The jumper wire and blinking check eng. light method has worked several times for me.Your factory manual should spell out how to retrieve codes with this method,and also give you the specifics on testing components.
FWIW, Pep boys has a sale on Actron code readers and scanners.The base model code reader is going for about $70, if I remember right.
With the systems that you're leaving off your engine,I think you might get quite a few codes set as soon as you fire it up.Buying a code reader might save you enough time to make it a worthwhile purchase.
GOOD LUCK,George
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Old 06-06-2005, 11:11 AM
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All you need to do is jumper terminal A to Terminal B with the ignition on and the engine off. it will then start flashing codes, it will start with code # 12 and go up from there, tell me what codes you have and I might be able to help

Steve
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