02sierraz71_5.3

iTrader: (2)

What causes the pcm to revert to the lower octane table?
Obviously if you run lower octane it should revert to the low table but how does the vehicle tell what octane you are running
What conditions are a deciding factor when it comes to choosing high/low tables?

horist

Several things determine... the octane of the gas you use doesn't matter unless you get knock

more knock = closer to low octane, less knock = closer to high octane... it's not a yes/no , use high or use low... it's a blending of both

having a knock sensor code, failed MAF, probably failed MAP and O2 sensors as well (basically if any of the primary sensors fail, it'll go into a limp mode and use the low octane table excuslively)

02sierraz71_5.3

iTrader: (2)

tttttttttttt

Bink

Yep, it's a proven fact..................as horist stated - it's a blend .


No need to -> ttttttttttttttttt.

John_D.

iTrader: (2)

Correct. If the knock sensors are reporting a lot of knock, it drifts down to the low octane table. If the knock sensors are reporting no knock, it drifts up to the high octane table. It just depends how much knock the sensors are reporting to the pcm.

WicketMike

iTrader: (13)

If its a blend like your saying, what would make it only read the low octane table?

i have some WOT runs on A-tap that i did yesterday and my timing is 19 thru the whole run, which is what the low octane table is set at.

I did about 4 runs, the first 3 i got KR right when i stabbed it. the last run i didnt get any KR.

If its only reading of the low octane table, do i have a serious problem?

Pro Mouse

iTrader: (15)

Yep it could be a number of things to send you into Low Octane table.Such as False Knock ,Just exaust banging the Floor board sent me into low Octane mode.