1995 Chevy Lumina Testing ALDL-OBD1 connector - ONLY piins

Tiny
LOUISRYOSHIN
  • MEMBER
  • 1995 CHEVROLET LUMINA
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 158,000 MILES
My 95 Lumina Sedan 3.1 L seems to run fine for 3 yrs siince I got it - well maintained before me as well. 2 weeks ago would not start but all else OK. Eventually found it was VATS key resistor sensor in ignition key cylllinder. I did standard key bypass cutting the 2 wires from it at base of steering column & soldering in a resistor of same value as key's. Works excellently. AAll else I did was disconnect battery terminals to clean them & unplug-plug oil pressure sensor harness as it was near srarter, and many fuses & relays one at a time - all while engine was off. Once car started again initial lights in dash work correctly. Then, when engine running (drive it or not) for 7-9 sec or so, Service Engine Light comes on every time. Never at immediate start - just waiting to that delay time of 7-9 sec. My ALDL or OBD1 or OBD1/2 combo connector under dash has only pins A=Gnd & M below it connected to the harness in a pig tail - black & dark or faded yellow or tan, a one colored wire. How do I test why light on? What is sequence of car computer test to get to that moment in its cycle. I tried shorting A=Gnd to M & no codes. Usual A-B short not work because no B pin. Light is on only since I did something on this repair. Same probelm before this was temp light moving up faster than it used to for last 6 months - changed radiator fluid-flushed & will do thermostat. But lSES light never came on for that or anything before, ever. HOW DO I TEST PINS A and M ONLY!
No pins 5.6 etc. My free mechanic friend tested with his GM testor twice and said he could do A G E F B --- and he got no codes out (maybe wrong pins)and tried to turn off light by pulling out EGM fuse and pumping pedals then replacing - light stays out intitally but 7-9 sec in engine running - comes on ech time. I have looked on line no help -and haynes Manual says some 1995 Lumina's do not have pin B and need a scan tool but all those I see require other pins besides GND and M. WHAT DID I DO TO TURN ON THIS LIGHT & HOW DO I TEST MY SYSTEM WITH PINS A & M ONLY. I have searched internetm dealership, auto part stores - to no success.
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Friday, November 14th, 2008 AT 9:39 AM

8 Replies

Tiny
DOCFIXIT
  • EXPERT
Hi
your car has no B. It is a pre OBDII system. You must have a GM Tech 1 scanner to get or to remove codes.
So it is dealer or maybe ebay to see if one is for sale.
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Friday, November 14th, 2008 AT 12:02 PM
Tiny
LOUISRYOSHIN
  • MEMBER
I already knew this - why pay you money for something I already knew. I was looking for an understanding of the pins.

I also found on my own the problem with a disconnected wire.

I am very NOT satisfied with this non technical answer - I could have called a local mechanic and gotten the same answer for free.

I would like my money refunded please.

Lou Gross
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Friday, November 14th, 2008 AT 12:20 PM
Tiny
DOCFIXIT
  • EXPERT
Ll you asked was where is trem B and how do I turn light off. Which I did. If you foind a loose wire what wire? You never said anythink about the wires out of connector and you did this in three hours. Well you have one big advantage you have the car I do I rely on you to give accurate information, Reread your post and see if it is remotly clear.
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Friday, November 14th, 2008 AT 5:08 PM
Tiny
LOUISRYOSHIN
  • MEMBER
Tnx for your reply - nice of you to stay in contact - for the connector - I am wanting to know what the wires M and A=gnd do to test it - and I have looked for scan units on line - the haynes manual says to use a scan unit if there is no B wire. So what you are saying is that the only way to check this is at the dealer's with an oscilloscope or special teser that can test just the M=serial output (per the haynes manual) and there is no such device nor information that meachnics outside the dealer have to explain what the scan testers do with their pins.

OK - not what I wanted to hear - but if that is the open door - ok - My local chevy dealer service agent head gave my tel nr to the mechanic who can help me after hrs the service guy thinks - less cost to me and it can help the mechanic as well.

Thanks for mentioning the wire. When my car stopped starting a few of use noticed this blue colored small wire in the front loom near the starter and the oil pressure-level sensor. Wires from the same loom bundle go to the solenoid start, +12 on the starter, and this oil sensor. And then this little blue wire that was found not long enough to reach anything except maybe the aoil sensor - but there are no more pins in the sensor itself nor in this connector to it that are available - the unit has 3 pins and the wire plug to it has three wires and pins.

But what I noticed today is that my Service Engine Soon light comes on (for the first time in 3 yrs of having the car) only since this non starting thing happened last week. That is, it shows after I got the car starting again with the resistor in the key sensor circuit because the key sensor is worn out, typially with these chevys.

And from a stopped car, starting it, all is normal and the car drives well, but after 10-12 sec of running, the SES light comes on and simultaneously the engine idle drops to 800 or less - from 900 where it was from start for the first 10-12 sec. The blue wire, when connected to gnd thru my analog multimeter on a 50 v scale shows 6 v when car is running, even when car was not running but the key was turned to start.

Now, when I switch the multimeter to the 10 v scale, the SES light does NOT come on. Same with 2.5 v scale. And on 10 v scale the voltage is more like 4.5-5 v. On 50 v and higher, like 250 v scale, the symptom of SES light and idle drop occurs and on 10 V and lower like 2.5 v it is not on.

In fact, if I start the car in the 50 v and then switch the meter to 10 v as it is running, the light goes out, and if I switch it back to the 50 v the SES light comes back on again.

Further, the 6 v (or 4.5-5 v) on the blue wire remains after I shut off the engine, whether the key is in ON or off or is removed from the cyllinder on the steering column - it stays on for 6-10 sec. And if I reinsert the key and start the car within the time the blue wire voltage is still on, the SES light will appear immediately on starting and stay on -- no 10-12 sec delay until it goes on. And if I restart the car immediately after - or later after the blue wire voltage drops to zero after its delay, then the car starts normally with the SES coming on after 10-12 sec. So there is some kind of delay built in.

The issue seems to be the resistance to ground for the blue wire - too much resistance and the idle speed is not up enough and the SES light comes on. Less resistance and it seems OK. At least that is the evidence I have so far.

And as I say, I don't know where to hook up the blue wire and the wiring diagram in the Haynes book does not show it, nor does the dealer parts guy have wiring diagrams at all on his computer.

And I have yet to find anyone who has the knowledge to analyze the pin M to GND in a special tester - probably an oscilloscope of some sort.

The usual way to find the codes for DIY on OBD-1 ALDL is to short pins A=GND and B=codes witha paper clip and read the flashes on the SES light - even the Haynes manual tells you how and gives the coe numbers and what they mean. But the manual also says not all the 1995 GM cars had pin B by manufacturer design, and for that it needs a scan tool or a dealer setup.

So this is the whole story.

The reason I am tyring to save money is that for some years I have been ill and I am on disabiltiy and my income is low so I am trying to DIY as much as I can. On that resistor substitute for the key I saved $175 over what a seeming nice mechanic wanted to charge me for disconnecting the anti theft module - now the module and all the circuitry is there and I can make an extension pair of wires up to the dashboard and put a connector on it, and then carry the resistor pack - a few of them - have them in my vehicle - and have both lower cost keys without the resistors and also have the security system, too.
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Friday, November 14th, 2008 AT 7:33 PM
Tiny
LOUISRYOSHIN
  • MEMBER
Sorry - I forgot to mention - my own local low cost mechanic does have a GM tester and I watched him connect it up on two consecutive days and he says he could get no codes out of it - nor turn off the SES light.

Later I found this wire resistance to gnd relationship of why the SES light comes back on. Of course, a clearing the codes and turing off the light only brings the car back to the pre error detection state, then when the car is started again it runs thru its sequence or monitors things that happen in the car operation. And when my car starts warming up and the idle drops to about where it should be, then the SES light comes on indicating the error.

If his GM tester - that he said has tests for pins A B E F G (but not M as in my car) then it would not be actually testing my car's codes. And the other brands of testors for OBD 1 I saw on the internet also have a number of wires required - and my car only has one wire besides GND - M.

So there is something to do with the resistance to gnd of that wire. And I am starting to just pull it out of the loom and see where it goes to at the other end. I got part way and ran into a hard physical place to get in with a junction of many bundles so I have to wait for daylight and the engine to cool and take off the air intake hose and filter box to get my fingers in there and see.

Lou
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Friday, November 14th, 2008 AT 7:41 PM
Tiny
DOCFIXIT
  • EXPERT
Hi louisryoshin
Thanks for reply and the info am going to dig into this and will call in some help to get you going. Could you give a phone number so I can call this works better in tough cases as this seems to be.
Hand in there I'll be in touch in an hour 11am EST where I am.
Is it 3.1L or 3.4L?
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Saturday, November 15th, 2008 AT 10:02 AM
Tiny
LOUISRYOSHIN
  • MEMBER
Home 321 726 9083 est 321 726 9083
cell if I am out 310 270 3297 310 270 3287
try calling both

where does the blue wire up front go
how do I check a connector with A and M

3.1 Liter
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Saturday, November 15th, 2008 AT 10:13 AM
Tiny
LOUISRYOSHIN
  • MEMBER
I want to compliment Ernie from cocoa (or was it cocoa beach) - he called me from there - I live not too far away - and he actually did research - and kew what the plug pins on my testing connector were for and what kind of testor was needed and when I then went over the info on my blue wire that was hanging in the front of the car - he saw what it was about and then contacted another mechanic and told me just where it was to go to and even walked me thru it when I went out to my car - and then when I found the wire - it was exactly the length that it needed to be to match the existing wire - and color - and to location - and it probably was the AAA guy messing with that area at night and even pushed the wire out of the way behind the knock sensor - the pnly explanation ebcause I never had the ses light on before in 3 yrs - and when the car first would not start right before that no ses light - but the very next morning another AAA guy came out and looked foe me - and saw this wire was hanging loose. So it had to be broken that night by the AAA guy.

I had been tot he dealer and also the auto parts store and had some idea about the sensors up there but fif not know about this wire neededing to be connected - and he was a big help - even the dealer mechanic did not know for the wire - and another web guy said it was an in needed wire as did other people. And my regular mechanic had notr used the correct testor for the plug either - so ernie is to be complimented for his knowledge and his going the extra mile to help me.

I am on disability and have not even enuf money to eat - but I will give a little more later.

Lou
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Sunday, November 16th, 2008 AT 8:47 AM

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