mrvedit

I have an LS2 engine in my '81 Camaro controlled by a '98 PCM (I know strange combo). When I bought this engine/PCM combo, it had been set up for only one O2 sensor and I therefore built the exhaust with one GM O2 sensor on the passenger side and a wideband O2 sensor (w AEM gauge) on the driver's side. I tune with HP Tuners. The MIL codes for the 2nd O2 are disabled.

It doesn't appear that the GM O2 sensor is ever controlling the PCM, it acts like it is always in open-loop. (Yes, my "Open loop enable coolant temp table" is correct.) In the scanner, I can see the GM O2 sensor output voltage swing correctly in conjunction with the wideband gauge. The A/F ratio seems completely controlled by the MAF table, or if the MAF is disconnected, by the VE tables. I have the MAF and VE tables "pretty" good now, but would prefer the O2 sensor closed loop operation.

So my question is - do I need to install a 2nd O2 sensor to get the PCM to work properly, or should just one be enough?
Based on another person's recent post about running to rich and then discovering he had his left/right sensors mixed up, does the PCM change the fuel to each bank based on that bank's O2 sensor?

Also, I have already bought a 2002 PCM and new connectors, and know that the connector pinouts are completely different from the '98 PCM. (My LS2 was retrofitted with a 24-pin reluctor.)

Question - what benefits might I see from switching to the 2002 PCM? Any drawbacks other than having to tune a new PCM?

Thanks!

mrvedit

Its a 2007 LS2 but with a 24x reluctor and LS1 sensors; it also has a 230+ duration cam and internal changes. It was removed from a car that ran 10.9. I think some GM engineers built it as an "exercise". (I'm in the Detroit area) The '98 PCM works perfectly with it; I have no doubt that the '02 PCM will work after re-pinning the harness. I just wanted to know what the advantages of the '02 might be, if any. I realize this is a strange engine. Obviously a lot of effort was put into modifying this LS2 to run a much older PCM; I think the goals were drive-by-cable and something that was easier to tune at the track.

The PCM also controls my 4L65E transmission perfectly.

Mostly though, I wanted to know if I really need two O2 sensors connected to the PCM; I am starting to think that I do.
Thanks.

mrvedit

Yes, an aluminum LS2 out of a 2007 Trailblazer SS.
Equally "entertaining" is the 4L65E transmission which I purchased brand new. It turned out to be a 2009 which is electrically incompatible with any previous year. First, the 3-2 shift solenoid was eliminated. More importantly, the "Pressure switch assembly" was replaced with a shift-linkage switch assembly. I therefore had to purchase a "broken" 4L60E, remove its valve body, rebuid it, install a shift kit, and get it all together. I learned so much that I now answer 4L60E questions on various forums. So I have a Franken-engine and a Franken-trans. Since my goal was to learn a lot, I have been very successful in that regard.

Agent_Orange_Shuvel

iTrader: (8)

From my limited tuning experience, yes you do need both front O2 sensors to have it operate in closed loop, as far as it making fueling adjustments to each bank I'm not sure, but that would make sense where they have seperate fuel trims for each bank. As far as the benefits from the 2002 PCM, if hp tuners does custom operating systems like efilive switching to the newer pcm will allow you to upgrade to one of those. But outside of that it sounds like a lot of work for not much gain.

mrvedit

Thanks, unless I hear otherwise, I'm leaning toward installing a 2nd O2 sensor, i.e. in the same bank as my wideband O2. Do love having a wideband A/F gauge though.

Pop N Wood

iTrader: (1)

LOL. Good attitude!

Agent_Orange_Shuvel

iTrader: (8)

Yeah, hard to tune without one. So if I understand you correct, your AEM wideband is in the opposite bank of the standard O2 sensor? If that's the case the AEM has an adjustable output, meaning if you aren't using the white wire for datalogging you can just change the little calibration screw on the back to P4 and the output(white wire) will act like a standard O2 sensor, so you don't have to install another sensor. But all this would only work if you are using the serial output(blue wire) for datalogging.

mrvedit

Yes, my AEM wideband sensor is in the opposite bank. Great suggestion! I'll have to find my AEM doco and confirm that my unit works as you say. That should hold me until it is convenient to weld in another O2 bung.

And I keep learning stuff!

Edit: Confirmed that my AEM 30-4100 gauge works as you say. However I have no idea what you mean by "But all this would only work if you are using the serial output(blue wire) for datalogging"; perhaps you meant "...not using...". I'll eventually put in another GM O2 sensor so that I can indeed perform wideband data logging with HP Tuners. Thank again for the VERY useful info.

Agent_Orange_Shuvel

iTrader: (8)

Well if you're not using the wideband for datalogging you could do what I said above no problem. I just figured since you had a tuning suite that you had your wideband hooked up for datalogging. Anyways efilive supports the 0-5v input and the serial connection for logging and I'm not sure about this but I would guess that hptuners can do the same. That way you wouldn't have to put another O2 in just utilize both the outputs of the AEM wideband. Did I mention I really like my AEM wideband.

bozzhawg

exactly, if he used the wideband he would still need to use both outputs right?

Bozz

Agent_Orange_Shuvel

iTrader: (8)

Yeah, use the white wire with the P4 setting to mimic the standard O2 for the PCM and the blue wire for datalogging.

82cetuner

iTrader: (9)

your ls2 engine was not retrofitted with a 24 tooth reluctor it came that way.

Only Corvette ls2s came with the 58 tooth reluctor same as LS1 corvettes had drive by wire and not drive my cable.

I would run duel 02 Sensors all it really takes is to drill another hole into your collector near the widband o2.

I have heard the 98 computer was not as good tuning wise than the 99 and later.

There is no problem running a Ls2 engine on a Ls1 computer it can be done all thats needed is a drive by cable tb, different fuel injector harness and a cam sensor extention wire and a few other small changes. and a Tune in the computer of coarse

mrvedit

Thank you for the correction. The book "How to Swap GM LS-Series Engines into almost anything" contradicts itself on whether 2007+ Vortec/LS2 truck engines are 24 or 58 tooth reluctor.

Agreed. It's just tricky as I have to remove the headers to drop the X-crossover exhaust system and then drill/weld another bung in. I plan to pull the engine/trans soon (to install an oil pan with more ground clearance) and will do it then.

That is what the consensus seems to be; I'm just looking for details.

Exactly what I have. I actually have it running very well now with near-optimum A/F in open-loop.

Thanks!

mrvedit

I bought a custom harness from www.ls1wiringharness.com in the exact configuration and length I wanted. However I had it made for a '98 PCM and would need to repin it for a '02.

I'm hoping a 2009 4L65E is fairly sturdy; my changes did not weaken it; the Transgo shift kit help too. I plan to buy another 4L65E and have it "built".

Like I said, my goal is not a "finished" car, but the learning process. I almost have it running perfectly now; once I do, I will pull the engine and trans and try something new and different.

Thank you all for your feedback! It has been very helpful.
BTW - I've been fairly active on www.nastyz28.com for one year, but will probably spend more time here now. My story and pictures of blowing up my 383 (split the crank, block and trans) was very popular:
http://www.nastyz28.com/forum/showthread.php?t=196932

Agent_Orange_Shuvel

iTrader: (8)

You would probably find more details on the difference between the PCMs on the hptuners forum.