OBD 1 and 2 difference

[weasel]

so my car was caught in a year when cars were going to OBD2,my car is that messed up OBD 1.5.whats the differences between a OBD1 and 2 chevy 3100 v6? as far as i know theres another O2 sensor but i dont know what else could be different.

[robertisaar]

if it's 95 and earlier, it's OBD1, if it's 96 and later, it's OBD2.

OBD1.5 as has been described for years doesn't exist.

[weasel]

i know the year difference but whats the differences on the engines?

[robertisaar]

engine specific? almost nothing. coolant temp sensor changed on most applications from a 2 wire + 1 wire sensor to either a single 2 wire with PCM controlling the dash or a single 3 wire that performs both functions.

the secondary O2 is post-cat, which isn't engine specific.

not OBD1 vs 2 specific, but starting in late 95, certain engines got the roller rocker setup, older setup lasted through 1996 in some engines.

all 96-up engines had MAF and MAP, not the either/or setup used from 93-95.

96-up use a linear EGR instead of the 3-tower digital.



may be more, but i can't think of them off-hand.

[pocket-rocket]

Obd1 is MPFI. Obd2 is SFI until 2k rpm.

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[3400-95-Modified]

Not correct on that pocket-rocket... 94+ Beretta's were tagged as OBDI with a SFI setup, they had the non removable prom ECU's in them though like the F-bodies, and IIRC it was till 3k or 4k rpm that the SFI functioned... otherwise it would be quite useless on the highway if it shut off at 2k.

[robertisaar]

after pouring through the 93-95 3100 SFI code, i'm not so certain they ever "switch" to batch-fire...

i really need a dual-input oscililiscope to verify it though.

[3400-95-Modified]

I was only told they do because the system can't keep up in firing sequentially at a certain RPM...

But if a mechanical spring/rocker setup can operate that quickly I can't see how an electronic part that's only open for ms at a time can't...

[robertisaar]

i don't see a reason why it can't.... i didn't see any code that would imply it did so either.

the faster the engine spins and the larger the pulsewidth, the benefits of SFI become less important/noticable.... but actually inserting code that would drop in and out of SFI based on RPM seems strange. the code to update the injector driver registers is VERY lean, so processing power/time isn't an issue.

[weasel]

so if i cant find a OBD1 engine for my car i can make a OBD2 work?

[robertisaar]

engines are not OBD1 or 2 specific.