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Octain rating:how can I get the car to tell me?

STS Scott

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Based on the tuitorial "93-95 OBD I Diagnostic Codes from Tony Haukap" in the FAQ section, I know the STS can tell me what grade of fuel it is running.

Can our DTS do the same, and how would I go about retrieving the info?

I ask because my Dad filled his car up at work, and someone told him it was premium grade, and we just wanted to check.


" ...'took my Cobra down t' the track, hitched to the back o' my Cadillac..."

- Jan & Dean, 'hey little cobra'


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STS Scott

Here is the process:

1. Get into the diagnostic mode------------Press OFF and WARMER at the same time

2. The the system go through the diagnostics

3. The system will end on PCM-------------Press the FAN UP ARROW

4. The first area is data----------------------Press the UP ARROW

5. Keep pressing the UP ARROW until you get ot ---PD-42

6. Read the Octane---It will read O or 87 or 90 or 93.

You can figure how to get out of the diagnostic mode.

Vince P

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I hear what you are saying, I can understand why it would take a longer time to update the tables and even why they are probably not that precise all the time.

I thought this was interesting and when I went out to my car on friday I went into the diagnostics and scrolled to PD 42. I was delighted to see that it said "87" haha which is the type of gas i've always put into the sts.

Anyhow, I thought it was pretty neat.


Christopher Petro

94 sts

67 coupe de Ville

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Hmmm... I tried this this morning, just out of curiousity. My data on PD42 was 0, so what exactly dos that mean? I just fueled up with 89 octane mid-grade yesterday, and that's all I ever run (unless I'm heading for the strip that is! B) ) I'm thinking it either means it can't get an accurate reading, or it has defaulted to a mode where there is no spark compensation?? :unsure:

'09 Cadillac CTS-4 3.6 direct injection, 128 K mi.
'15 Chevy Tahoe LTZ, 5.3i V8, 125 K mi
'70 Firebird Formula 400, Bored+.04, RAIII heads, M21 4spd., in-process restoration!

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