A few people have asked in the past if it would be possible to use an "earlier" generation OBD2 PCM from something like a 98 Venture Van (3400) with a newer design 60 deg V6 engine. The 3500 (VVT and non-VVT), 3400 LNJ, and 3900 (VVT) engines all have a single internal crank trigger which differs from what the 3400 LA1 and 3100 V6's used. All 3400 LNJ, 3500s, and 3900s come with drive-by-wire throttle controls and a newer generation ECM which is more sophisticated than earlier OBD2 PCMs, which can complicate things when trying to do an engine swap using this “advanced” technology.

3100 and 3400 LA1 V6's use two separate crank sensors; the 7x (mounted in the block) drives the coil pack, base fuel and spark functions while the 24x (mounted behind the balancer) was thought to only be used for misfire detection. The newer generation 60 deg V6 engines use a single sensor which connects directly to the ECM, which in-turn, drives the ignition coils directly (which makes the newer gen engines directly incompatible with earlier generation OBD2 PCMs and OBD1 ECMs).

Currently, you can buy an external 7x crank trigger wheel and sensor setup from WOT-TECH which gives you the ability to use a new generation 60-deg V6 with an older OBD1 ECM. But that trigger wheel mounts outboard of the crank pulley and there's no provision for a 24x sensor on it. It might be possible to use a 3100/3400 LA1 timing cover on a newer gen V6 - which if you could do that, it would give you the provisions to run the 24x crank sensor. But I'm not sure the WOT-TECH external 7x sensor would work with such a setup since what they sell appears to be designed to work with the timing covers and crank pulley assemblies that come on the newer gen V6's. And the question has always been: will an "older gen" OBD2 PCM work properly missing the 24x crank sensor input? Today I found that out...

I unplugged the 24x sensor and disabled all related codes for it, misfire detection, etc on a 1999 3100 V6 application I had in the shop. I went on a drive and, initially, the engine ran just as it had with everything plugged in (stock). Everything looked to be operating normally on the scan; but once I went to full throttle, the engine fell on its face and a code P0327 set (which is for the knock sensor). I did some looking thru the service manual and here is what I found:

quote If either the 24X crank sensor or the cam signal are not present, the KS signal will stop updating and may set DTC P0327.

Furthermore, the service manual had this to say about the 24x crank sensor signal:

quote The 24X reference signal is used to improve idle spark control at low engine speeds. The PCM uses the 24X reference signal to calculate engine RPM and crankshaft position at engine speeds below 1600 RPM. The PCM constantly monitors the number of pulses on the 24X reference circuit and compares the number of 24X reference pulses to the number of 3X reference pulses and CAM signal pulses being received. If the PCM receives an incorrect number of pulses on the 24X reference circuit, DTC P0336 will set and the PCM will use the 3X reference signal circuit for fuel and ignition control. The engine will continue to start and run using the 3X reference and CAM signals only.

With the 24x sensor unplugged (and all codes relating to it disabled), I never saw any activity on the knock retard data. Which leads me to suspect that the PCM might suspend using the knock sensor signal entirely if there is no 24x crank sensor signal received.

WHAT DOES THIS MEAN? Well, if you want to use a 3400 LNJ, 3500 (VVT or non), or 3900 VVT V6 in a swap with something other than the newer gen ECM that was originally used with one of these engines, your ECM/PCM choices might be limited.

The 1998~2005 OBD2 PCM architecture is what I refer to as the "Gen2 OBD2 PCM". A slightly larger, less sophisticated PCM was used the previous 2 years (1996-97) which I refer to as the "Gen1 OBD2 PCMs". Interestingly, researching the service manual on these “Gen1” OBD2 PCMs and the code P0327 shows that there appears to be no impact on the KS circuit function if the 24x crank signal is missing. So it MIGHT be possible to use one of these earliest generation OBD2 PCMs with only a 7x crank sensor signal (and a cam sensor signal if you want SFI to work).

I don't currently have access to a vehicle that is using a 96-97 OBD2 PCM in it to see how it reacts to not having the 24x crank sensor signal going to it. But hopefully, one day I will so I can test it. It would be nice to be able to use a Gen1 or Gen2 OBD2 PCM with one of the newer generation 60 deg V6 engines. These PCMs are cake to tune vs. the newer drive-by-wire ECMs, and are easier to tune vs. the older, OBD1 ECMs like the stock Fiero 2.8 ECM and the 1227730 ECM – especially on modified engines.

-ryan

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OVERKILL IS UNDERRATED

Custom GM OBD1 & OBD2 Tuning | Engine Conversions & more | www.gmtuners.com

Interesting post and good info. Nice preview of the challenges of engine management facing new V6 swap choices.
In the past the 3.4L, 3800SC's, 3.4TDC, 4.9L's and SBC variations have been popular swap choices but as time goes on Fiero engine swaps will probably migrate to more state-of-the-art engines. Now that ETC, DIJ, VVT and CAN control is the norm its going to make it more difficult to do a swap, in particular an auto swap. Aftermarket ECM's should always be available but they do not always give the ideal solution. Unfortunately the choice of ECM's/PCM will become more limited and swaps will become far more involved. We can always develop new techniques for engine swaps but the days of the simple swap appear to be be over unless one wishes to use old technology .
At the moment the 3400, 3500, and 3900 60* V6 engines appear to be choices for a current technology GM engine.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

Let's clarify one thing... we're talking about the 7x reluctor wheel on the older hardware vs. the 58x reluctor wheel on the newer hardware.

Did the first 3500's still use the 7x reluctor wheel? I didn't think GM introduced the 58x wheel in anything until after the 3500 came out, but I could be wrong.

Also, the newer PCM's don't have to be limiting. With 58x wheels and common PCM's across their entire engine lineup, the non-recurring effort involved in hacking them is much less.
For example, the 58x LS2/3/4 PCM's are already hacked. How far away is the tuning package for the 58X computers? I thought HPTuners already had it.

quote Originally posted by Will: Let's clarify one thing... we're talking about the 7x reluctor wheel on the older hardware vs. the 58x reluctor wheel on the newer hardware. Did the first 3500's still use the 7x reluctor wheel? I didn't think GM introduced the 58x wheel in anything until after the 3500 came out, but I could be wrong. Also, the newer PCM's don't have to be limiting. With 58x wheels and common PCM's across their entire engine lineup, the non-recurring effort involved in hacking them is much less. For example, the 58x LS2/3/4 PCM's are already hacked. How far away is the tuning package for the 58X computers? I thought HPTuners already had it.

It isn't a 58x reluctor. The service manual says it is still a 24x signal but it is different than earlier crank sensors because this one is mounted in the block and there is no 7x sensor/reluctor at all. Here is what the service manual says about it:

quote The crankshaft reluctor wheel is mounted in the middle of the crankshaft. The wheel is comprised of three 120 degree segments. Each segment represents a pair of cylinders at top dead center (TDC), and is further divided into six 20-degree segments. Within each 20-degree segment is a notch of two different sizes. Each 120 degree segment has a unique pattern of notches. This is known as pulse width encoding. This pulse width encoding pattern allows the PCM to quickly recognize which pair of cylinders are at TDC. The reluctor wheel is also a dual track, or mirror image, design. This means there is an additional wheel pressed against the first wheel with a gap of equal size to each notch of the mating wheel. When one sensing element of the CKP sensor is reading a notch, the other is reading a set of teeth. The resulting signals are then converted into a digital square wave output by the circuitry within the CKP sensor. The CKP sensor is a three wire sensor based on the magneto resistive principle. A magneto resistive sensor uses two magnetic pickups between a permanent magnet. As an element such as a reluctor wheel passes the magnets, the resulting change in the magnetic field is used by the sensor electronics to produce a digital output pulse. The CKP sensor returns a digital ON/OFF pulse 24 times per crankshaft revolution. The pulse width encoding pattern is used to synchronize the coil firing sequence with the crankshaft position. The CKP sensor is used for ignition timing, fuel injector timing, misfire diagnostics, and tachometer display. The PCM supplies a 12-volt reference, a low reference, and a medium resolution engine speed signal circuit to the CKP sensor.

No 3500 (or 3900) was made with the older style 7x / 24x crank sensor setup. When GM introduced the 3500 in 2004, it came with the new generation ECM and DBW throttle body. GM even modified a version of the 3400 V6 (LNJ) so it used the same hardware.

HP Tuners has cracked many of the ECMs used with these newer generation engines, and it can disable VATS in many of them. But as people are finding out, not everything works in an engine swap application when using these newer generation systems. For example, things like cruise control may not function at all in a DBW swap if you don't also swap in the BCM from the donor car. Same thing goes for the A/C compressor controls. Many of these functions run thru other modules or depend on other sensors connected to other modules (like the brake pedal position sensor - which is wired up to the BCM) in order for these subsystems (like cruise control) to be enabled. To further complicate things, I don't think the 3500 was ever used with a manual transmission. The 3900 was, but only for a few years. This can be a problem because most of these applications used a separate TCM (transmission computer) which must be linked to the ECM in order for both modules to work. And it isn't yet clear to me if a DBW system for an engine that was never used with a manual transmission will function properly if there is no auto trans present.

At least we got lucky in the fact that GM saw fit to equip the 3900 VVT pushrod engine with a manual transmission for a few years (and this application did not have a TCM present). So that at least opens the door to people who want to use one of these newer engines with a manual trans and keep the VVT system in that engine working.

Trifecta supposedly has the swap PCM's figured out for the 3.6 DI, but that's a 58x configuration (I assume that the High Feature/Alloytec V6's use the 58x wheel). I think there are applications which are/were built with both pushrod and Alloytec engines, so the network interface should be similar.

Should just take time now.

I really like the parts Joseph Upson was making. He had tone rings made up so you could press the 24x off the crank and put a 7x on in its place. Unfortunately he would neither sell me one nor send me his cad file so memy non-vvt 3500 still sits on the floor in the garage. At first I couldn't get behind the idea of the external crank sensor, and now WOT-TECH is backordered.

quote Originally posted by Darth Fiero: Currently, you can buy an external 7x crank trigger wheel and sensor setup from WOT-TECH which gives you the ability to use a new generation 60-deg V6 with an older OBD1 ECM. But that trigger wheel mounts outboard of the crank pulley and there's no provision for a 24x sensor on it. It might be possible to use a 3100/3400 LA1 timing cover on a newer gen V6 - which if you could do that, it would give you the provisions to run the 24x crank sensor. But I'm not sure the WOT-TECH external 7x sensor would work with such a setup since what they sell appears to be designed to work with the timing covers and crank pulley assemblies that come on the newer gen V6's. And the question has always been: will an "older gen" OBD2 PCM work properly missing the 24x crank sensor input? Today I found that out... -ryan

For reference I have the very set up you're talking about running in my car. It is a 2005 3400 LNJ using the TCE (WOT Tech) 7x external crank trigger running a 98 PCM.



As you all can see, here is the 24x sensor bolted into the stock timing cover. GM decided not to remove the bolt holes for it I guess. All you need now is a Balancer with the 24x wheel on it.



My stock 3400 LNJ pulley on the left and a junk yard 3400 LA1 pulley on the right. Now I wish I took the picture from the other side so everyone could see the 24x ring.



And then here is the external 7x trigger installed to complete the set up.

I believe the 3500 has the same timing cover as my engine and a 24x sensor can be bolted on. The 3900 on the other hand I'm not sure about.

quote Originally posted by KaijuSenso: I believe the 3500 has the same timing cover as my engine and a 24x sensor can be bolted on. The 3900 on the other hand I'm not sure about.

There's a possibility that the 3500 *NON*-VVT has the same front cover. The 3500 VVT would have the same cover as the 3900.

Well at least that gives us good news that the WOT-TECH 7x external crank trigger will work with one of these newer engines (non-VVT) and at the same time allows you to also use the 24x crank sensor behind the balancer. With both these sensors present, you should have no problem using an LA1 OBD2 PCM to run your engine. You will, however, need to use the LA1 knock sensor instead of the stock one that came in your newer generation 3x00 engine.

quote Originally posted by KaijuSenso: For reference I have the very set up you're talking about running in my car. It is a 2005 3400 LNJ using the TCE (WOT Tech) 7x external crank trigger running a 98 PCM. http://a7.sphotos.ak.fbcdn....830054_6255237_n.jpg As you all can see, here is the 24x sensor bolted into the stock timing cover. GM decided not to remove the bolt holes for it I guess. All you need now is a Balancer with the 24x wheel on it. http://a6.sphotos.ak.fbcdn....830053_1585329_n.jpg My stock 3400 LNJ pulley on the left and a junk yard 3400 LA1 pulley on the right. Now I wish I took the picture from the other side so everyone could see the 24x ring. http://a1.sphotos.ak.fbcdn....932505_3245744_n.jpg And then here is the external 7x trigger installed to complete the set up. I believe the 3500 has the same timing cover as my engine and a 24x sensor can be bolted on. The 3900 on the other hand I'm not sure about.

quote Originally posted by Darth Fiero: Well at least that gives us good news that the WOT-TECH 7x external crank trigger will work with one of these newer engines (non-VVT) and at the same time allows you to also use the 24x crank sensor behind the balancer. With both these sensors present, you should have no problem using an LA1 OBD2 PCM to run your engine. You will, however, need to use the LA1 knock sensor instead of the stock one that came in your newer generation 3x00 engine.

Intredestating.

my non VVT's timing cover also had the boltholes for the 24x sensor, I swapped my cover though, because my cover was broken. the later balancer doesn't have the 24x ring as KaijuSenso pointed out, replacement balancers for a 3400 bolt on though, and cost about $40 new at O'riellys.

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I know these lines Look crooked on paper, but I swear I've got them straight in my head.

I'm considering doing the LX9/F23 swap and have a couple more questions re: the LA1 PCM. I'm assuming that stock sensors (MAP, MAF, knock, ECT, IAT, CPS, ICM, etc.) from the LA1 will also be used along with the FPR and fuel rail.

1. Any problems using the stock tune with a manual? I'm not too concerned about codes as long as the PCM doesn't limit normal operation (ie go into limp mode).
2. If needed, I can plug in a transaxle range switch to tell the pcm the car is in drive, or is there a better way? Resistor or jumper wire/switch?
3. Does the PCM need the fuel pressure signal from the fuel tank sender/pump assembly? VSS as well?
4. Should I use the 3500 injectors or the 3400 injectors? I may make some minor mods in the future but peak hp likely won't go over 220-230 hp.
5. I'm assuming that the spark map will be close enough to run the 3500 despite the slightly higher compression ratio (9.8 for the 3400 at 9.5) and I'm also assuming that the MAF and MAP will compensate for airflow variations caused by headers; yes?
6. I know the block learn should take care of most of the tuning while in closed loop but does the adjustment also get applied to the fixed fuel map at full throttle? I have a wide-band O2 kit that I'll be using to verify proper mixture but am wondering what to expect.

TIA!

[This message has been edited by mender (edited 06-24-2012).]

quote Originally posted by mender: I'm considering doing the LX9/F23 swap and have a couple more questions re: the LA1 PCM. I'm assuming that stock sensors (MAP, MAF, knock, ECT, IAT, CPS, ICM, etc.) from the LA1 will also be used along with the FPR and fuel rail. 1. Any problems using the stock tune with a manual? I'm not too concerned about codes as long as the PCM doesn't limit normal operation (ie go into limp mode).

Usually you have to have the VATs requirement programmed out of your PCM, in which case you might as well have them fully tune it for your application. You could also use a VATs signal emulator.

quote 2. If needed, I can plug in a transaxle range switch to tell the pcm the car is in drive, or is there a better way? Resistor or jumper wire/switch?

See above

quote 3. Does the PCM need the fuel pressure signal from the fuel tank sender/pump assembly? VSS as well?

Fuel
No on the fuel pressure, however many modern cars check the AIR pressure of the tank and will display a MIL (SES) code with the fuel tank air pressure sensor missing. Again you can get your PCM reprogrammed at a very reasonable price and not have to deal with these headaches.

VSS
Manual transmission PCMs are programmed to idle the engine higher between shifts. They are also programmed to not interpret a long downhill throttle closed event as a problem high idle event. So yes the PCM wants/needs to see the VSS input.

quote 4. Should I use the 3500 injectors or the 3400 injectors? I may make some minor mods in the future but peak hp likely won't go over 220-230 hp. 5. I'm assuming that the spark map will be close enough to run the 3500 despite the slightly higher compression ratio (9.8 for the 3400 at 9.5) and I'm also assuming that the MAF and MAP will compensate for airflow variations caused by headers; yes? 6. I know the block learn should take care of most of the tuning while in closed loop but does the adjustment also get applied to the fixed fuel map at full throttle? I have a wide-band O2 kit that I'll be using to verify proper mixture but am wondering what to expect. TIA!

If you are running close to stock, you can use stock injectors.

MAP and MAF will accommodate minor variations in air flow, however don't expect them to cover large ones.

[This message has been edited by phonedawgz (edited 06-24-2012).]

So is there a base tune available for a reasonable cost for this combination?

Is $ 85 reasonable

http://www.gmtuners.com/eprom/index.htm

Very; thanks for the link!