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Reset PCM Octane setting?


gc_caddy

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Due to recent high gas prices, I've been running 87 octane for the last little while. I have noticed absolutely no knocking. I think I may be losing some performance though, but it's very hard to tell.

I checked the diagnostic PCM data value PD42, and it now shows that 87 octane is being detected. (Cadillac's sure are smart!)

Anyways, I'm thinking of going back to higher octane fuel now - feeling a little guilty.

Is there a way to quickly reset the PCM octane setting? Does anyone know how long (or how many tankfuls) it will take before the PCM recognizes the higher octane? Thanks.

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I'm not sure why you would want to do it manually. I think you should just switch back to the fuel you want to use and let the computers handle it, that's what they're there for.

If you really want to make people safe drivers again then simply remove all the safety features from cars. No more seat belts, ABS brakes, traction control, air bags or stability control. No more anything. You'll see how quickly people will slow down and once again learn to drive like "normal" humans.

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I don't believe the octane readout is a settable function. I think it is set by the knock sensor; more knocks = lower octane readout.

-George

Drive'em like you own 'em. - ....................04 DTS............................

DTS_Signature.jpg

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Just fill the tank with premium. The knock sensors will not detect spark knock and the timing will not be retarded. I would think the response would be immediate.

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But if you really want to reset the codes, i would guess that if you disconnect the battery for a few minutes that the codes will get cleared. The owners manual says to let the car idle for some period of time after re-connecting the battery so that the system will program itself. Presumably this is the type of thing that its talking about.

Just a guess.

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Regular and Hi-Octane have the same "power" therefore you will feel no difference. The ingredient in Gasoline that gives it "power" is Heptane. All brands, have the same Heptane. Changing the Heptain level makes it something besides gasoline. Perhaps lacquer thinner, or choclate pudding, but it won't be gasoline. Octane is added to SLOW the burn process, to prevent pre-ignition in higher compression engines. Older high compression piston engine aircraft used up to 130 octane levels. Low octane, i.e. Regular burns faster...use the lowest octane rated fuel, until your car "pings". Keep adding or increasing octane levels until it stops. That is the bottom line period. My '92 Seville STS doesn't even like 91 octane. That is the highest we can get here. My '99 thinks 91 is ok...

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... The "octane table" will reset itself very quickly as the knock control system determines/sees that there is no spark knock. The system is constantly "trying" to advance to the next higher octane table anyway and the continued onset of detonation with the lower octane fuel prevents it. With premium in the tank it will advance to the correct spark table within just a few minutes of driving....or less.

=

Thanks Bob... It's reassuring to know that the Northstar is on constant guard to give us the absolute best performance, as quickly as possible.

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