Blown WS6

I just picked up an LT1 out of a 94 Caprice complete with EVERYTHING except the PCM to put in my 92 Vert. But while I was at it I thought about how hard it would be to switch over to OBD II? I would like to use the newer system. I like the extra diagnoses capabilities of OBD II. But for Smog legality I was wondering if I am going to have to have a working Evaporative monitoring system. That would suck. I do know I am going to have to a) take my car to a smog referee for the swap. I then would need ALL the existing emissions equipment for it to even pass a visual. OR b) get a smog license myself and then just pass the thing myself as long as it doesn't have to go to a test only station. I already have all my regular ASE's and my L1 advanced engine performance so all I'd have to do is take a few classes at the community college and take the test with B.A.R.

Would going to OBD II just require a few differant parts and sensors? Or would it be not worth my effort? Does the OBD I system on the 94 monitor misfires since it is Opti-spark? That is what I really like about OBD II so I don't have to hunt down why i have a rough running engine.

Any info appreciated.

I'm going to check out what i can find with my All-Data account about the Misfire stuff.

pasky

So you want the ability to diagnose which cylinder is mis-firing and a crank position sensor? What for? Stick with OBD I, it'll save you a lot of money.

Blown WS6

Can i do that without having to switch to OBD II? That is a HUGE time saver when you have a problem. I have a miss on my TPI motor right now and its really buggy. I try to kill cylinders manually by removing plug wires from the distributor and I still can't really tell by rpm drop. Its an odd problem though like a broken valve spring on the exhaust valve (vacuum stays dead steady)

Anyways back on topic, yeah thats the main reason. After talking with one of the smog techs in my shop today I decided that even for the misfire ability I wouldnt want to go OBD II. But I'd still like to know if I can somehow get the OBD I system to diag misfires. Thats be uber-cool.

pasky

OBDII is not a hassle because of the extra sensors, its a pain in the *** because its far more expensive to program for. You can get a cable and tuner cat for $120 while programming OBDII requires LT1 edit and a special cable and the total is around $500. There is no reason to switch to OBDII on a lt1. If a cylinder is misfiring its either wiring or the opti. Since you cannot adjust the opti it really does you know good to know which cylinder it is.

kairles

iTrader: (2)

didn't all LT1 cars have the 16 pin DLC and a crank sensor also

I also like OBDII for its diagnostic's, must be a technician thing

Klortho

93 and 94 cars has the older OBD1 connector, and 95 used the OBDII connector but used OBD 1, 96 and 97's started using OBD II.

GMTech

Most OBD-II cars set a P0300 which is a general misfire. Out of probably 100 cars, only one will set a specific cylinder DTC, i.e. P0302.

As far as LT1s, all the ones I have seen didn't have a way to monitor individual misfires. Early 3800's had "Current Weak Cylinder" listed in the data display. Misifire counters and graphs didn't show up until maybe 1997 or later? So you may not find what your looking for if you go OBD-II.

If all your looking for is "ease of diagnostics", going OBD-II may not be worth the trouble, just my opinion.

Blown WS6

Sorry, actually a P0300 is multiple misfire and is ALWAYS set when three or more cylinders are misfire or they are random.

So most cars will set the specific cylinder FIRST, i.e. P0302 for cylinder #2. Then if they have more then two cylinders missing or random mulitple misfires then it will set a P0300.

pasky

Not worth the trouble IMO, if you do decide to go that route you will need it programmed for vats and the 2 rear o2 sensors and it will be substainely more expensive. The disadvantages outweigh the minor benefits.

Klortho

Plus wouldn't he either have to use the wiring out of a 96-97 model to get the other 2 O2 sensors and the PCM? Sounds a little pricey just to get that you have a misfire. I know a guy with an Impala SS that swapped his from OBDII to OBD I so it would be easier for him to tune.

GMTech

LMFAO, get your nose out of the books and turn some wrenches .
Of the thousands of GM cars and trucks I have worked on in the past 6 years, about 1% have ever set a cylinder specific code. I have had cars come in with 50,000 misfires and counting on cylinder #1 and ZERO on every other cylinder, yet a P0300 was the ONLY code.

I know how the misfire codes are supposed to work and I also know how things happen in real life.

Blown WS6

LOL! Do you really think that NO ONE else here is a Tech? I am a Dodge certified tech and ASE master Tech. I have worked on PLENTY of GM's and Fords (along with everything under the sun) when I worked at CarMax. I've been doing it for 6 years as well. Go out and go unplug a coil pack on an LS1 and go see what code it sets!! I read your post on our MDS2 computer in the shop and all the techs started laughing! EVen our apprentices know you are wrong. DAMN!


I just don't go bragging in my sig and my member name I am this high and mighty tech. But at least I know more then you do!

Blown WS6

Maybe you should stick you painting cars if you are "certified" in that! LOL!

GMTech

So I'm wrong because of the cars that come through the door have a P0300 stored? Like I have any control over that? Get a clue. Even on cars/trucks that allow use of the misfire graphic on the Tech2 and show a dead misfire on one cylinder, usually have a P0300 only stored. Its a programming issue, out of my hands. I can only work with what I got, so how does that make you and your apprentice smarter then me?
If you see a ton of cars that set a cylinder specific misfire code, thats great, consider yourself lucky because we don't get the feature very often. Perhaps you see it more because your in CA and California emissions are a little tighter on diagnostics then the federal emissions.

FWIW, I'm an ASE Master w/ Advanced level as well, but I don't "tout" them because everybody knows that if you can fog a mirror, you can pass those tests. They are a joke.

Blown WS6

If you think ASE's are a total joke thats fine. The L1 had a fair level of difficulty to it. But yes anyone who is good at studying and taking tests can pass them. They complement experiance with good book knowledge.

Anyways, back to the subject at hand, OBD II is a nationwide standard and not relative to GM or California or any of that. I can take a Honda from Texas and do the same thing. At CarMax we had transfers from other stores in other states and the same thing happens. First a cylinder specific code. If more then two cylinders then the P0300- Multiple misfire. A Tech2 or a DRB III (Mopar's scan tool) or an NGS (Ford's scanner) or my generic MAC OBD II scan tool will say the same thing. I can take my DRB III and go to OBD II monitors and select the Misfire monitor and find out EXACTLY how many misfire counts each cylinder has. I know the NGS has the same feature. Play aroung with the Tech2 a little more and you will find a similer feature.

I know GM dealerships specialize their Techs. ( I worked at Braley and Graham Pontiac, Buick, GMC) Maybe you aren't doing alot of drivability? Are you the front end/brake guy? Dodge doesn't specialize and neither does CarMax. I do quite a bit of drivability. I'll admit though, I wasn't drivability at GM so I am not a total expert. I was a light line tech.

GMTech

OK, I'll bite. '00 LS1 F-body. No DTC's set, no misfires logged in history on shown current on misfire graphic.

Test 1: Disconnected coil as per your suggestion. CEL started flashing to indicate catalyst damaging misfire. Looked at misfire graph and history to verify dead misfire on cylinder one and ONLY cylinder one. DTC P0300 and P0351 (IC #1 circiut) were stored.

Test 2: To do away with the P0351 code, I plugged the coil back in and removed the spark plug wire. I cleared all DTCs and re checked. Current misfire on cylinder 1, and only a P0300 stored.

Now since your my intellectual superior, surely you'd be glad to explain that to me why your test didn't reveal the results you told me I would get.


Whole point is, I don't see how you can tell me I'm wrong when your not in my shoes, seeing what I'm seeing. I was just trying to offer advise based on experience from the field to help you make an informed decision. If I didn't think my information was legit, I wouldn't have posted it. If you think I'm full of crap, thats fine, you don't sign my paycheck so there is no need to impress. Just take my advice with a grain of salt and move on.

Blown WS6

This is why I doubt your tests.

Yet then you say you got the cylinder specific code of a P0351 (Coil circuit #1 open or something like that right?) when you unplugged the coil on the LS1! So that must have been the one car out of a hundred right? That was the whole point was that you had a misfire and it told you what cylinder it was at. You said that was incorrect. Your misfire graph said right there that #1 was misfiring.

I think you are a bit confused. I have never seen a P0300 without its respective cylinder misfire. You say that you never got the P0301 on this LS1 you tested. Well I'm not there and I know what I see every day.

You never answered my question. Are even a drivability tech at GM?

Either way you want to look at it you info wasn't correct for the situation I was talking about.

GMTech

See, now your making stuff up. I never posted that I saw a P0301, and a P0351 IS NOT A MISFIRE CODE. Sure, P0351 did isolate an IC circuit fault with cylinder #1, but IC circuits faults were never the topic of conversation. Misfires were. I think your lost and are tweaking facts to suit you. I've been doing drivability for GM since I started there back in 1999, as well as automatic transmissions. The P0351 did isolate the cylinder, but unplugged coils are hardly ever whats wrong with the cars (or is that how you upsell work????) How about when I just unplugged the plug wire??? Why didn't it then set a cylinder specific misfire code???? High resistance in a plug wire is more common then an unplugged coil, but the DTC didn't isolate it and thats what I have been getting at.

Sure, the PCM can isolate IC circuit faults, injector driver faults, etc.... but like I said from the very beginning, it has been my experience that most of the misfiring vehicles don't set a cylinder specific misfire code, i.e. P0302, but a P0300 instead.

five7kid

iTrader: (14)

What say we get

Blown WS6

GMTech I even mentioned that the P0351 isnt a misfire in my post. Please read it fully. Then you accuse me of being a dishonest tech? Grow up.

GMTech

Actually, I think this is on topic, because we are debating Pros/Cons of OBD-II, because it is in a way, part of the question.

My whole argument was P0300 -vs- P0301-P0308. Most of the misfiring vehicles I work on, wether it be a whole bank of cylinders misfiring, or just one; a P0300 code is all the misfire codes it sets. I either have to use the Misfire Graphic if current or Misfire History to establish the suspect cylinder.
Now, assuming we do have an open circuit to an injector or ignition coil, then YES, the PCM is able to isolate the offending cylinder. However, when its been a bad plug and/or wire, restricted injector, bent pushrod, leaking intake gasket, bent valve, etc.... the misfire code has not isolated it for me, I had to dig deeper via graphic and/or history.

Now, I posted a poll on the GM Technicians website about P0300 -vs- P0301-P03XX and so far 82% responded they see a P0300 only when diagnosing a single cylinder misfire. Since you used to be a GM tech, if you still have the Service Information login, you can view it here: http://service-gm-forum.com/techforu...howtopic=13118

Now, I'm not going to say either one of us is wrong because, the small percentage that reported seeing a P0302 on the example I gave, reported it was with an aftermarket scantool, NOT the Tech2, which I personally own so I use it exclusively. That may explain why we are not on the same page. Why an OEM scantool would be less specific than an aftermarket is beyond me.

Blown WS6

I wouldn't be able to view it anyway because I haven't worked at GM since 2001. They remove your name/pass once you are gone. Well they are supposed to.

Think about it logically. Why would the OBD II system NOT kick out the specific cylinder misfire code if it knows the cylinder that is missing? The whole purpose of those codes is to tell the tech that is working on it which cylinder is misfiring.

Example: when I was working at CarMax I did a ton of 3.1L and 3.4L intake gaskets. You should know about those intakes on how they like to leak every 30K miles. And you also know how when you do intake gaskets you have to remove the unequal length pushrods. Well I was rushing through one on a black Grand Am with a 3.4L and I must have not got the #2 cylinder intake pushrod centered because when I started it the pushrod fell out of underneath the rocker. So its running a little rough and I have a SES light when I started it up. I pull codes with my generic OBD II scanner and get a P0302. NO P0300. It doenst matter when scan tool I pull the code with. The vehicle doesn't know. It only talks to the scanner on three majorly used protocals. Either ISO 9141-2, Keyword 2000 or another one that I forgot the name. Anyways, there are a few dealer specific protocals as well but they aren't for any OBD II codes and functions because OBD II is universal.

So there was a GM vehicle with no P0300.

GMTech

I can't explain it, just know thats how its been and made my comments based on that. We can argue this forever, nothing will change.

The last protocall you were thinking of was Class 2, but GM is now phasing in GMLAN to make things more complicated

And the passwords have not changed, its the "universal" login thats always been around. Its Dealerworld that always changes now, and is the portal for Service Information. Other features still use the "old" login. You should read it if you can, its interesting, and you'll see I'm not alone by a long shot.

Blown WS6

No that's a GM specific protocall. Like Dodge's CAN-B and CAN-C Bus. I'll find out the other one later.

And also like I said. I worked for GM back in '01. Not gunna remember any passwords from back then. I don't even remember our dealer code.