LS1-450

iTrader: (33)

What on the crank shaft triggers the crank sensor? Is the trigger the same on a 98 LS1 crank/assembled block as it is for a 2006 LS6 crank/ assembled block? Is the crank sensor itself the same, (mechanically & electrical output) on a 98 crank sensor & a 2006 crank sensor? The 98 sensor was re-used & remains connected to a 98 PCM. The same is true of the cam sensor & all other sensors; 98 sensors & 98 PCM are used.

We have had an electrical issue since the swap & remain searching for the cause. Engine cranks, but, will not start. Cannot connect to the PCM.

DrkPhx

iTrader: (15)

Have you verified fuel pressure at the rail?
It should be between 55-60 psi at the rail.
Is this a LS6 (5.7L) crate motor?
GM last installed the LS6 in the 2005 CTS-V
Are you getting code PO335?
This will set if the PCM does not read a crank signal for less than 3 seconds.

The LS1 and LS6 both have 24X (24 teeth) reluctor wheels pressed on the backside of the crankshaft. When the crank sensor has voltage it creates a magnetic field that is interrupted by the reluctor wheel as the crank turns. This produces the actual signal which is read by the PCM. It is not a mechanical sensor.

You can try a new crank sensor or test with a known good sensor. Double check the battery voltage as well. The crank sensor needs a good strong signal. You may have check the wiring from the PCM to the connector for the correct voltage, but save that for last.

I would also check the plugs and oil for gas fouling and contamination. The repeated cranking may have ruined the plugs.

Finally double check to make sure the PCM has solid grounds to bare metal.

LS1-450

iTrader: (33)

-There's no fuel or spark.
-The new assembled LS6 block was installed to replace an original LS1 block w/ #5 & #7 piston failures. The assembled block is brand new. The AFR heads were re-built & all other engine parts remain as in signature.
-Don't know if it's throwing codes as we cannot conect to the PCM.
-The PCM voltage has been confirmed & is properly grounded. PCM pin outs have been checked.

It's difficult to find because it's a conversion where Miata gauges are used & Miata BCM sensors are connected to a GM PCM. Additionally, there is a Viper security system tied in that may be adding to the problem.

I asked about the crank sensor thinking that maybe there was a mechanical diffference. Thanks for the explanation.

Am hoping to get more insight tomorrow. A guy who takes care of the electrical interface for this type of conversion will be available to discuss what's happening tomorrow. We keep coming back to the Viper alarm system. Am not sure how, but, wouldn't surprise me to find out that it may have some thing to do w/ this. Maybe the crank voltage & fuel pump relay trigger power have been routed from the PCM through the Viper & out to the sensor as theft protection. Hopefully, we'll have better answers tomorrow.

All that was done was to swap the LS6 block for the LS1 block & then re-assemble the top end...etc. & re-connect the sensors & grounds. The Viper security system did some funky stuff when we powered up initially & VATS is dissabled in the PCM.

Thank-you for the advice. Your crank sensor explanation was especially helpful. I'll re-post any progress.

DrkPhx

iTrader: (15)

No problem.

I would definitely disconnect the alarm system and try to start it. If the PCM is getting voltage and sending it out it almost has to be the alarm system.

LS1-450

iTrader: (33)

DrkPhx,

The guy we spoke w/ today said that the LS6 block will not run w/ a 98 PCM because the LS6 uses 58 teeth on the crank & the LS1 uses a 26 tooth (I think it was 26) could have said 28 or something. The point being that the car will not run as long as the 98 PCM & sensor is counting more teeth on the crank. Does that make sense? How would that make us not connect to the PCM? Thanks

Randy WS6

iTrader: (69)

have you checked the fusses , i could not conect to my pcm and it was a acc.fuss blowed, it on the side of the dash between the drivers door.,I beleave it was a 20 amp fuss.

LS1-450

iTrader: (33)

Thanks for the suggestion. Yes, all fuses have been checked. We found that the tooth count difference between an LS1 & LS6 crank is the no-start cause. Don't know if changing the reluctor is the better solution or a PCM/sensor swap. Any opinions will be appreciated.

I still believe that the Viper security system is the cause of the no-PCM connect. We are trying to find out how it was wired. The Viper system was installed w/ far too many fail safe curcuits. We've requested more information about the Viper system & hope that the connection issue resides there. There are @ least two if not more relays effected by the Viper. In regards to the PCM/reluctor solution, have asked for help in the tunning/PCM section as well.

DrkPhx

iTrader: (15)

Sounds like you're getting mixed information. It's true the reluctor wheel count must match the PCM; otherwise it will not start. The fuel pump, injectors and ignition coils are referenced off this signal. But all Gen III engines (LS1/LS6) use a 24X reluctor wheel on the crank which means they are compatible between the LS1 and LS6. GM didn't switch to the 58X reluctor until mid-year 2005 for the LS2 and new LS7.

Which leads to a different question; Are you sure this is a LS6 block with a LS6 crank? More importantly, did a shop build the shortblock for you and maybe installed the wrong crank/reluctor wheel? I know it sounds odd, but you never know. The only way to tell at this point is to physically count the teeth on the wheel.

You need to disconnect the crank sensor connector from the sensor and check to see if it's getting the correct voltage with the ignition switch ON.

Was the alarm system installed before or after the new engine?

DrkPhx

iTrader: (15)

Just for clarification. Here's some information from a non-sponsor website. Note directly from the website:

GM PART # 12559353
DESCRIPTION: CRANKSHAFT RELUCTOR WHEEL 24X 97-05 LS ENGINES

LS1-450

iTrader: (33)

Thanks, the block is a 2006 LS6 assembled block. The GM dealer has confirmed that all 2006 GM cranks LS6, LS2,LS7 have 58 teeth. Even though, we need to count them as you have suggested. We really don't know for sure until we look & 24 teeth are required.

I think we can count teeth w/ the sensor removed by turning the crank shaft. If not, we'll have to pull the oil pan & count. We will check the sensor voltage as well. The no connect to the PCM through the OBDII connector remains an issue.

DrkPhx

iTrader: (15)

I would call Brian at Scoggin Dickey (SDPC - sponsor here)>> to confirm that information. If GM did that, it seems it would cause alot of problems with people like you retrofitting a newer block into an car with an older PCM.

LS1-450

iTrader: (33)

Called SCPC. They have confirmed that brand new 2006 assembled blocks & cars w/ motors assembled in 2006 are shown to have 58 tooth reluctors. Although, 2006 LS6 crate motors are shown to have 24 tooth reluctors. Based on my car not starting & the overlap of 24 & 58 toothed reluctors slated for LS6 motors in 2006, there is more than a good chance that my crank has a 58 toothed reluctor. Have also e-mailed the block assembler to see if they can confirm which reluctor was used. We will count the teeth to be sure. Still don't know how this relates to not being able to communicate w/ the PCM.

DrkPhx

iTrader: (15)

Wow. That's good to know. Why in the world would GM do that; especially if someone needs an engine replaced under warranty? That would cause a big headache. The reluctor wheel is used for engine start up only.

jay_99z

iTrader: (5)

The difference in teeth will have no affect on the PCM. It has no way of knowing how many teeth the crank has. Just what it is programmed to. In your case...24.


That sucks man.

LS1-450

iTrader: (33)

Well, after all of that, it turns out that the reluctor installed on the crank is the 24 toothed reluctor. It was confirmed by the block assembler late today. So, we remain in the dark as to the problem. At least the change from 24 to 58 in 2006 production vehicles has been noted & it's something for others to be aware of in the future. As noted, GM LS6 crate engines remain assembled w/ the 24 toothed reluctor & 2006 LS6 production engines use the 58 toothed reluctor which began sometime during the 2006 production year. There is likely some overlap.

The Viper alarm system & the reluctor have been eliminated. I think that this is a problem that won't reveal itself until we actually run across it or them. Could be several issues. We still need to check the power @ the crank sensor as you suggested. Maybe that will reveal something. We'll keep looking & more suggestions are welcome & appreciated.

DrkPhx

iTrader: (15)

At least that's out of the way. Do you have a scan tool? If not you need one.

Some quick checks:

* Verify battery voltage and make sure engine cranking speed is ok (not slow).
* Crank the engine for 15 seconds and check for any DTC's.
* Verify rpm are showing on the scan tool when cranking the engine.
* Disconnect crank sensor, turn ignition ON (engine off) and check the ignition feed
wire (light green) for voltage (12.0v).
* Do the same for the camshaft sensor and check the red wire for voltage (12.0v).
* Verify the VTD (vehicle theft deterent) is "Active". Inactive (disabled) indicates the PCM is not receiving the signal to activate the fuel system. In your case the anti-theft feature should be set to "None."

LS1-450

iTrader: (33)

Which scan tool is sufficient? Would also like to be able to make simple tune chages to timing, fan on/off temp settings,...etc.. I want something that allows me to save the current tune & change minor stuff as needed.

DrkPhx

iTrader: (15)

For your application you need a robust scanner/tuner. There's HPTuners and EFILive. I use EFILive and really like it. Either one is expensive and requires a laptop. But it's money well spent and a worthwhile investment that will pay for itself almost immediately because of the flexibility and convenience. Don't ask which one is better because this thread will get locked.

www.efilive.com

www.hptuners.com

LS1-450

iTrader: (33)

So..................here we are four months into it. Most of the time w/ the car sitting in a shop parking lot collecting bird droppings.

I had the car flat bedded back today & the car was in the same non-running condition as it was four months ago. Good news was that the shop had installed the oil restrictor that was missed when the block was installed previously. Honest mistake though; neither the shop or I had had experience w/ a new LS1 or LS6 block & did not know about the restrictor.

Called my friends @ Diamond/Manning motor sports. These are the guys who build LS1 Miata's & LS1 Miata kits. They've never let me down & have always been helpfull. Long story short.....the ground to a 30Amp power feed burried below a Miata fuse box that fed power to a GM fuse box & relay panel had lost its' ground. The power was @ the fuse, but, couldn't get to the GM stuff 'cuz of the lost ground. This fuse is burried & would likely not have been found without speaking w/Barry from Manning. Although, I don't know why the local shop here told me that the PCM had power & ground because when I checked it @ home today there was none. Anyway, a difficult problem has been resolved & everyone had the best of intensions while trying to work through it.

Also, thanks DrkPhx & all whom posted here.

Now, to hold idle I have to feather the pedal while the RPM's jump from 5000 to 25000, but, expect things to settle down after she runs a bit. Any comments about this? I also need to replace a coolant hose & connect some aftermarket gauge senders & she'll be ready to drive......I hope. Won't know for sure about the LS6/LS1 gremlins until I drive her a bit.