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SES light on.


alleyyooper
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My 1985 Buick Limited collectors editon is a OBD I computer car with a 307 Olds engine. It has developed  a SES light on mystery.

 

Took it to a shop thinking they may have a decated reader but they have the same fork tool I have. They checked it and said it was a O2 sensor problem and for $150.00 they would repair it.

 

I can do that my self since I used to work on Cadillacs, Oldmobiles and Pontiacs I have a 02 sensor socket and being retired have the time. The new bosch sensor was about $20.00. I removed the old sensor and found a little soot on it but not what I would call really bad, installed the new sensor unhooked the battery for a while to clear any codes, then hooked it back up then started the engine.

 

It ran fine and the SES light was off for a bit, then with a warm engine the SES light is back on so I shut it off.  I get my own factory supplied fork tool install it in the ALDL connector A/B turn the ignition switch on and get 1-2  another 1-2.  long space then 1-2>1-2 Factory manual for a 1985 Oldsmobile 98 says the first two flashes 1-2 say computer sees the fork tool shorting A&Bat the aldl connector, the pause  then 1-2 1-2 in suseestion is code 12 for the crank sensor fault, Is this code 12 the same for the Oldsmobile 307 engine in my Buick?

 

This has been going on for a few week ends now, A week ago with the outside air temp at 39F the light turned off as I drove 100 plus miles to a car show. It can back on during the return trip home with a outside temp in the 70F range.

 

I do have some black duct tape I could use to cover this dash lite. I see no difference in drivability of the car just the anoying SES light on.

 

 

?    Al

Edited by alleyyooper (see edit history)
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An O2 sensor code ALMOST NEVER means a bad O2 sensor on cars of that vintage. It means that the reading the computer saw from the O2 sensor was not normal. This probably means the fuel mixture is out of range, either too rich or too lean. Since you found soot, probably too rich.

 

Code 12 does mean no signal from the ignition. In plain English it means "engine not running". If I remember correctly, it will always be there.

 

Good luck with your project!

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With unleaded fuels, I believe the "light soot" you saw is somewhat normal.  If it had been "heavy soot", it would probably indicate a rich mixture that might overheat the cat converter if the  issue was not fixed.

 

Rather than look for "rich", think "lean", which might indicate a vacuum leak in the multitude of vacuum lines on that engine.  Look for fissures rather than  breaks, which might become larger with temperature increases.  There should also be something similar to an "ambient air temp sensor", possibly, somewhere in the intake manifold (later on intake air ducting on FI engines).  With a vacuum leak, the computer will try to and can cover for some smaller ones, but not the much larger ones.

 

Does the cruise control still work?  Reason I inquire is that on some later GM cars, there was a vacuum check valve near the cruise servo that was known to break with age, putting a small fissure in one of the vacuum nipples.  Enough to bleed off the vacuum to the cruise control, but not enough "leak" to cause an engine miss.

 

Trouble codes were manufacturer-related, rather than carline-related.  GM wasn't the same as Ford or Chrysler codes AND could change with the model year of the vehicle (from one year to the next), with OBD II, they were standardized across all OEMs.

 

You can chunk parts at "codes", but unless you understand the dynamics of WHAT causes those codes, you've just replaced parts (now rather than later), by observation.

 

NTX5467

Edited by NTX5467 (see edit history)
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7 hours ago, NTX5467 said:

 

You can chunk parts at "codes", but unless you understand the dynamics of WHAT causes those codes, you've just replaced parts (now rather than later), by observation.

 

This is SO TRUE. It is doubly true on those older models. Don't adjust anything. Not yet. On those old cars the codes are a CLUE, nothing more.

 

If this is what I think it is, an olds 307 with a Rochester Dualjet carb and GM CCC electronic engine control, there is a wire somewhere you can hook a dwell meter (set to 6 cylinder scale) and see the mixture adjusting itself. You should see the mixture running about 30 degrees at idle and cruise. This is 50% on a duty cycle meter if you are using one of those instead of a dwellmeter. IIRC it needs to be completely stuck at one end of the range or the other to set the code.  About 6 degrees and not moving is what stuck looks like at one end of the scale. I don't remember what stuck is at the other end. Probably about 53. For the moment I don't remember which is rich and which is lean. I think 6 degrees is stuck lean. To really run right it should be at 30 degrees and moving around a little bit.

 

As NTX5467 said, vacuum leaks are common. This system wont tolerate any vacuum leaks. None. You will have to fix them all. Over-rich due to a sunk carb float is another extremely common problem.

 

Good luck. Let us know how it goes.

Edited by Bloo
.. (see edit history)
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Man I sure wish people would read all of the post posted instead of just part of it.

 

I also say thank you all for attempting to teach me some thing but the problem code isn't the )@ sensor I was told it was if ya'l had read what I wrote.  Go Bye.

 

Also the code 12 I was getting off the ECM was a hard code since the engine was not running.

 

:D     Al

 

 

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That Olds 307 should have the electronic QuadraJet, rather than the electronic DualJet 2bbl (the front half of a QuadraJet).

 

One common issue with the carbs was with the solenoid which ran the metering rods up and down (indicated by the "dwell" reading mentioned above).  In the metering control solenoid, there obviously is some red/orange seal material.  When the solenoid has an issue, you'll probably find little rings of that material in the bottom of the float bowl (after you get to the top of the carb and get it removed).  These "rings" reminded me of orange silicone rubber in color and consistency.  Sometimes, just small pieces rather than complete rings.

 

Rather than the prior "Power Piston" which runs the metering rods, the E4MC electronic QJet uses a "metering package" of the solenoid, primary metering rods, and primary jets.  GM didn't provide any specs on the jet sizes or metering rod sizes for these set-ups . . . just part numbers for particular carburetor numbers.  

 

Even with the newer OBD systems, if there are several codes in the computer, it's necessary to write them all down, see where they came from, and look for common issues that might have caused them to be stored in memory.  In some situations, ONE malfunction can trigger several other related codes.  Just as in the prior times, knowing how everything works together is important, especially as fuel issues and ignition issues can cause similar problems . . . just like in the old days.

 

So, take the codes you've retrieved, find the applicable 1985 GM code list, consider what might have caused it/them to set, research and diagnose accordingly.  Please let us know what you find.

 

NTX5467

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Code 12 flashed means your in to get codes. Codes should flash. The code 12 will flash again indicating code reading is complete.  If O2 sensor is indicated 99% of the fault code is anything but the O2 sensor. Check for vacuum leaks and the ignition. Also, old car with old vacuum lines. Check each will the engine is running. Sometimes the old hoses get soft and collapse from vacuum. 

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Check the canister purge valve.  Look on your under hood vacuum diagram to locate it.  They can cause a lot of drivability problems and intermittent check engine lights.  When vacuum is applied to the top port (the one that is supplied vacuum from the carb) it should hold vacuum.  There should be no fuel visible at this port. If either of these conditions exists the diaphragm is ruptured and the valve needs to be replaced.  Good luck.

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The canister purge valve, when it has issues, can make the carb go full rich and "fog mosquitoes" from the rear exhaust pipe.  LOTS of carbs were rebuilt trying to fix that, when all it was was the purge valve.  On some years, they are on the top of the canister itself, so you get a new canister.

 

NTX5467

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