OBD2 LT1 XDF $EE EEX creation

[steveo]

i'd be doing some disassembly at this point.. you have a lot of input now to label some things, and track those back to identify the code responsible for them. there are lots of things you wont be able to find the way you're going at it. for example where's the switch to disable the crank sensor? that one is pretty important for 96-97 cars with huge cams.

[Tom H]

where's the switch to disable the crank sensor? that one is pretty important for 96-97 cars with huge cams.

Hi Steveo,

Could you explain a bit more about how a large cam needs the crank sensor code disabled? This is stuff I don't know enough about...

-Tom

[steveo]

the crank sensor on these engines is only there to feed the OBD-ii misfire detection requirement. it compares the cam and crank angles i suppose and if they're too far off it figures there's a misfire.

you can imagine how the cam to crank relationship looks with a really lumpy cam. it causes the timing chain to jog back and forth a lot and cause the same kind of result as a real misfire.

the check engine light flashes if that happens. that might be a good clue, if you can find a routine that looks like it's flashing the CEL rather than just sticking it on, you could probably track that back and find the memory containing the error bit, then go back from there and find the misfire detection code.

it'd be nice to find the parameters so you could widen the angle that it considers a misfire and still retain some misfire detection, but other tools don't have that so people tend to just disable the error code so their dash doesn't blink at them. also the misfire detection doesn't SEEM to do anything other than flash the light, but nobody is 100% sure about that

[Tom H]

it'd be nice to find the parameters so you could widen the angle that it considers a misfire and still retain some misfire detection, but other tools don't have that so people tend to just disable the error code so their dash doesn't blink at them. also the misfire detection doesn't SEEM to do anything other than flash the light, but nobody is 100% sure about that

I am sure (?) I can find it, once past these programming routines I will take a look. You are talking about the dtc.. right? There is a table where each dtc can be disabled/enabled. I sort of remember that there are four classes. I will refresh and post back later.

Somewhere in the last 25yrs I was told by someone (sort of vague?) that misfire was done by looking at the time between hi-res ticks. If she fires, the momentary acceleration of the crank would reduce time to the next tick. That & the
operation of the crank sensor beyond looking for the disable is probably a fall task. That is unless we all get locked down.
Easy to see how a lumpy cam would mess with all the crank acceleration stuff also.

-Tom

[steveo]

i dont know if the DTC is separate from the misfire detection code flashing the check engine light...it does both

[Tom H]

i dont know if the DTC is separate from the misfire detection code flashing the check engine light...it does both

If your car is like the 96/7 Camaro/Firebird, I can give you a suggestion in a few days that *should* stop the lights. Can you tell me what code it is throwing??

[steveo]

i don't have a car
from memory it sets that obd-ii code called random misfire

[Tom H]

the crank sensor on these engines is only there to feed the OBD-ii misfire detection requirement. it compares the cam and crank angles i suppose and if they're too far off it figures there's a misfire.

you can imagine how the cam to crank relationship looks with a really lumpy cam. it causes the timing chain to jog back and forth a lot and cause the same kind of result as a real misfire.

the check engine light flashes if that happens. that might be a good clue, if you can find a routine that looks like it's flashing the CEL rather than just sticking it on, you could probably track that back and find the memory containing the error bit, then go back from there and find the misfire detection code.

it'd be nice to find the parameters so you could widen the angle that it considers a misfire and still retain some misfire detection, but other tools don't have that so people tend to just disable the error code so their dash doesn't blink at them. also the misfire detection doesn't SEEM to do anything other than flash the light, but nobody is 100% sure about that

Hi,

From what I can tell, the DTCs related to the crank position sensor are these.

P0300 ENGINE MISFIRE DETECTED: RANDOM/MULTIPLE CYLINDER
P0301 CYLINDER 1 MISFIRE DETECTED
P0302 CYLINDER 2 MISFIRE DETECTED
P0303 CYLINDER 3 MISFIRE DETECTED
P0304 CYLINDER 4 MISFIRE DETECTED
P0305 CYLINDER 5 MISFIRE DETECTED
P0306 CYLINDER 6 MISFIRE DETECTED
P0307 CYLINDER 7 MISFIRE DETECTED
P0308 CYLINDER 8 MISFIRE DETECTED
P0335 CRANKSHAFT POSITION SENSOR CIRCUIT MALFUNCTION
P0336 CRANKSHAFT POSITION SENSOR CIRCUIT RANGE/PERFORMANCE


I think we can eliminate anything with a "CIRCUIT" in the name because no amount
of cam can affect continuity of the sensor. My thinking is that the P0300 would
be the code I would expect. In the '97 code I see a table of enables for DTC processing
starting at $20B0, 17bytes deep. Each bit controls the processing of a DTC, set is on. I believe
that clearing bit 7 of $20B4 will eliminate the DTC P0300. It would be more interesting to work
through the code to see if a parameter in the calibration can be change to eliminate the DTC at idle where
the impact of the cam is setting this thing off.

-Tom

PS: This table would be a good thing for the XDF to have...

[sherlock9c1]

I added that bit to my draft XDF, but what indexing are you using? 20B4 is 00 in both a '96 B-car BIN and a '97 F-body BIN, and both are in a field of 00s.

Is that in the E side or the T side? I'll email you.