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.
Friday, November 14th, 2008 AT 7:33 PM