code reader for GM

I have a 94 Pontiac Bonneville. The check engine light goes on sometimes. At idle, the oil pressure oscillates up and down. The check engine light usually goes on after going high speed
and slowing down to a stop.
I have tried to find a code reader for it. The connector is trapezoid (D-shaped). This is supposed to mean that the computer is OBD II, but since the car is a 94, it was during a hybrid year and needs a OBD I to OBD II adapter.
Can anyone tell me a way to read the codes?
Jon
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Jon G. wrote:

They both have rounded edges. obd2 is truncated trap - 16 pins. obdi is D shaped - 12 pins. A 94 should be obdi.
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« Paul » wrote in alt.autos.gm

The problem is that in 94-95 GM used the OBDI system with an OBDII connector. Dealers usually have the scanner, but that, of course, costs alot of money just to have the codes read.

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Dick C wrote:

Hmm.. I'm probably wrong but I thought GM did not start using the obd 1.5 until the 95 model year?
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« Paul » wrote in alt.autos.gm

Late 94 I think.
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Hi,
thanks for your help all.
My OBD II connector has pins 4,5,8,9,14,16 populated. This doesn't match *any* of the standard configurations for OBD II scanners (there are 4 protocols). From what I can determine, the pinouts are,
pin 4 chassis ground pin 5 signal ground pin 8 ? pin 9 signal ? pin 14 CAN Low (J-2284) pin 16 battery power
Then someone wrote,
"Yes, some OBD-II equipped vehicles have a hybrid system where the PCM is OBDII and the other modules in the vehicle are pre-OBDII, 8192 baud UART. The vehicle will typically have a PIM (Powertrain Interface Module) that converts the OBDII to 8192 UART and back again to facilitate comms between the two different systems.
The OBD-II connector uses pin 9 to provide access to the 8192 UART data of the non-OBDII modules."
Can I jump 2 of the pins for a flashing Check Engine light code readout? If so, which ones?
Dick C wrote:

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Jon G. wrote:

How do you know your aldl is what you have described above? You cannot jump pins to flash codes. You need a reader capable of reading obd 1.5. In other words, some of your car is obd 1 and some is obd 2. Call around and find a shop with a reader.
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« Paul » wrote:

If it's OBD I, you can jump two of the pins. Under the hood it says the car is OBD I compliant, but under the dash it has and OBD II connector.
the female looks like,
---------------------------- \ 1 2 3 4 5 6 7 8 / \ 9 10 11 12 13 14 15 16 / -----------------------
the following pins are populated:
pin 4 solid black pin 5 black with white stripe pin 8 black with white stripe pin 9 tan pin 14 green pin 16 orange
compare this with the OBM II protocols:
J1850 VPW pins 2,4,5 and 16 ISO 9141 pins 4,5,7,15 and 16 J1850 PWM pins 2,4,5,10 and 16
Short-circuiting pin 4 and 15 of an SAE J1962 connector for 3 sec gets the check engine blinking.
The pin configuration on my car doesn't match any of the OBD II scanner protocols. Will a code scanner still work? If the car is and OBD I with an OBD II connector, then which pins do I jump to pull a code from the blinking check engine light?
Jon
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Jon G. wrote:

Hi...
Dunno if it'll help to clarify things a bit, or just muddy the waters more, but...
Mine is the 12 pin system. (and I have a mickey mouse reader for it). The pins are lettered (opposed to numbered) and according to the book that came with the reader A is ground. B is the diagnostic test terminal. Shorting A and B causes the check light to flash the codes.
My Haynes book says for the 12 bit type I need only short A + B... and it works... but for the 16 bit type I would need a reader.
Ken
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Jon G. wrote:

I have never heard of anyone ever jumping pins on obd 1.5 and getting more than a burned out ecu. It has always been my understanding that you need a obd 1.5 reader - which is a obd 1 serial reader that can interpret some obd 2 data. You could try it. There are many people who would like to know how to do it. If you can figure it out, please let alt.autos.gm know.
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I've got a 94 bonneville SSEi. Bought an Actron OBDI reader and a cable to connect to the car with the OBDII type connector, works great.
Look on Ebay.
Or take it to the dealer and pay 'em a few bucks to tell you the code. Cheaper than trying to guess the problem and buying unnecessary parts. My dealer charges about $30 to just read a code. Sometimes they do it for free. If I need them to diagnose the exact problem they charge me about $55. Which applies to the repair cost if I let them make the repair.

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Hi Jeff &
I think the idea was to use an OBDII scanner to read the OBDI system, since OBDII scanners often read OBDI as well. I don't know this for sure. Under the hood the car is labeled as OBDI compliant, so likely it's OBDI with an OBDII connector. If this is the case, your Actron OBDI reader would work on my 94 Bonneville as well. Thank you for your insight.
I have a friend who has an OBDI reader. Maybe all I need is the adapter cable. I could do without the reader or cable if I only knew what the OBDII connector wires/pins, correspond to the OBDI connector, and jump a couple of them for a flashing check engine light code readout.
Jeff & Carol wrote:

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Something's going on here.
If I buy and Actron OBDI reader, complete with OBDI and OBDII cables, then I could map how the OBDI reader converts to OBDII pinouts, with an ohm meter, testing continuity between either ends of the cable for each pin, and then correllating.
Jon
Jeff & Carol wrote:

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Im a GM technician, You can not get this system to read out thye DTC'
(codes) by shorting the data lines in the aldl as you can in the ol OBD1 a previous poster is correct. GM devleoped a special adapter which included electronics-it is not a pin in/out adapter, used wit the tech 1 scanner, to cover the transition to OBD2. Once the Tech2 cam out they were backwards compatable with the previous system (supposedly, but a Tech1 still works better on the old stuff) If you dealer will scan it for only $30 you are getting a good deal. We ge one hour, $72. Even if you get the code, without books they ar usless. As my drivablity guy says, if you have oil pressure and you not running hot dont worry about it. 90% of the code are just emision related BS that mean very little in how tha car is reall running...........
-- Bun Bu
born in 59 grew up in Arcadia Ca. served in the army from Dec 79 to Ja
84 worked for a number of security companies filling posiotions fro guard to manager. Became a electronics technician for GM in 95. Married to an outstanding person and gotTrackpads.com! Community Forums, Gallery, more! 150,000 Photos, 3,000 Videos and growing! http://www.trackpads.co
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"user551" wrote: > Im a GM technician, You can not get this system to read out > thye DTC's > (codes) by shorting the data lines in the aldl as you can in > the old > OBD1 a previous poster is correct. GM devleoped a special > adapter, > which included electronics-it is not a pin in/out adapter, > used with > the tech 1 scanner, to cover the transition to OBD2. Once the > Tech2s > cam out they were backwards compatable with the previous > systems > (supposedly, but a Tech1 still works better on the old stuff) > If your > dealer will scan it for only $30 you are getting a good deal. > We get > one hour, $72. Even if you get the code, without books > they are > usless. As my drivablity guy says, if you have oil pressure > and your > not running hot dont worry about it. 90% of the code are just > emisions > related BS that mean very little in how tha car is really > running............ > > > -- > Bun Bun > > born in 59 grew up in Arcadia Ca. served in the army from Dec > 79 to Jan > 84 worked for a number of security companies filling > posiotions from > guard to manager. Became a electronics technician for GM in > 95. > Married to an outstanding person and gotTrackpads.com! > Community Forums, Gallery, more! 150,000 Photos, 3,000 Videos > and growing! http://www.trackpads.com
The dealer I got to charges $102.50/hr... That’s why I bought the warranty...
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I would suggest going out and getting a copy of the CHILTON manual for that particular car.
I have a '94 Chevy Blazer and have to read the codes myself. For my particular model I just jumper pins 1-2 with the ignition OFF. When I turn the key to the ON position, the 'check engine' will start to blink giving you the error code. The pattern varies with the problem, and the Chilton's manual will have the codes listed.
This is a quick way to determine what the computer has in it's memory.
Craig

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