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750WHP club :P
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Discussion Starter #1
Howdy, old member haven’t been on here for a while.
Back story on this car:
Bought from a member here, had to have the motor redone shortly after new cam swap. Sleeved LS3 418(417?) stroker. Had good shop do a hone on it forgot what it came out to and put it back together. Shop forgot to clean out intake that another member of shop said to clean out because there was metal in there from the failure. Car blows up on dyno. Shop made good and covered the damage. Ended up going with a 427ci since it needed to be redone anyway. So motor has been taken out twice and reinstalled at this point. Get the car back shortly after car has issues with dropping RPMs and jumping all over the place before ultimately dying. Car was unreliable to drive. Apparently was crank position sensor issue. Take to shop and have the issue diagnosed(after car sitting for a while) and fixed with new sensor. Take car home, drive here and there for a little and then same issue. Was told by shop to check the wires off the crank position sensor. Well working all the time and family life got in the way and this car was moved from spot to spot never driven but down the street and back due to the issue it was having. Would go above 3k rpms in 2nd and it would go crazy. Never really got any enjoyment out of it since the build was done and probably only a couple hundred miles on the motor. Finally found some time to take a look at this; HPT shows code being thrown of
P0336 also P0552 for speed sensor.
I have attached a picture and would like to know if the wires going to the sensor look like factory. It looks not like factory to me but wanted To see what others thought. I searched some threads on starter replacement and the code that was thrown itself to see if I could locate a picture showing the loom but I did not locate any pictures to help. Wanted to get this drivable so my wife can drive it in the summer time so any help is appreciated! Also attached the picture of the codes HPT pulled off it.
500441
500442
 

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750WHP club :P
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Discussion Starter #3
If that tape is flaky and brittle, yeah, it's factory.

Have you tried doing a CASE relearn?
No I haven’t. I came across that in my searches but only after I took the starter off. So I’m going to replace the crank sensor and VSS in the trans since I’m getting that code as well. Hopefully this fixes the problem because I found no issues with the wiring. If not then it probably means something is wrong with the reluctor which obviously is from the motor being put together but at this point it’s been so long.
 

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Howdy, old member haven’t been on here for a while.
Back story on this car:
Bought from a member here, had to have the motor redone shortly after new cam swap. Sleeved LS3 418(417?) stroker. Had good shop do a hone on it forgot what it came out to and put it back together. Shop forgot to clean out intake that another member of shop said to clean out because there was metal in there from the failure. Car blows up on dyno. Shop made good and covered the damage. Ended up going with a 427ci since it needed to be redone anyway. So motor has been taken out twice and reinstalled at this point. Get the car back shortly after car has issues with dropping RPMs and jumping all over the place before ultimately dying. Car was unreliable to drive. Apparently was crank position sensor issue. Take to shop and have the issue diagnosed(after car sitting for a while) and fixed with new sensor. Take car home, drive here and there for a little and then same issue. Was told by shop to check the wires off the crank position sensor. Well working all the time and family life got in the way and this car was moved from spot to spot never driven but down the street and back due to the issue it was having. Would go above 3k rpms in 2nd and it would go crazy. Never really got any enjoyment out of it since the build was done and probably only a couple hundred miles on the motor. Finally found some time to take a look at this; HPT shows code being thrown of
P0336 also P0552 for speed sensor.
I have attached a picture and would like to know if the wires going to the sensor look like factory. It looks not like factory to me but wanted To see what others thought. I searched some threads on starter replacement and the code that was thrown itself to see if I could locate a picture showing the loom but I did not locate any pictures to help. Wanted to get this drivable so my wife can drive it in the summer time so any help is appreciated! Also attached the picture of the codes HPT pulled off it. View attachment 500441 View attachment 500442
The reluctor has to be matched with the ECM and must be indexed. Mismatched wheels probably won't run at all, out of phase will act like the timing being off back when distributors ruled the roost. By your description I would look at that, the off the wall running characteristics indicate an ECM that is 'hunting' for the timing it wants to see, may run ok within the 'window' but go ape s___ outside of it, like it goes insane when exceeding 3000rpm.
 

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750WHP club :P
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Discussion Starter #5
The reluctor has to be matched with the ECM and must be indexed. Mismatched wheels probably won't run at all, out of phase will act like the timing being off back when distributors ruled the roost. By your description I would look at that, the off the wall running characteristics indicate an ECM that is 'hunting' for the timing it wants to see, may run ok within the 'window' but go ape s___ outside of it, like it goes insane when exceeding 3000rpm.
By indexing would that be the relearn procedure for the crank position sensor? I have HPT is that something I could look up on there?
Yeah so the car was tuned with the new motor without issue after the new motor was done. This issue developed within a few months of having the car. Then brought back in and had the crank position sensor replaced. I’m guessing a relearn was done on it. And if I recall they test drove it several days before giving it back. Then the same issue popped back up within another couple months. I’m hoping this is not the reluctor wheel being off in the motor or it shifting over driving. If that’s even feasible to occur. I’m going to get the loom on the wires and button it back up and go from there. It was electrical tape wrapped around the wires. I checked my other GTO and it’s all an actual loom didn’t realize it was that easy to see from the engine bay. The wires on it did not look damaged. Also checked the ground on the back of the head and that seems fine.
 

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If you replace the motor or the crank sensor, you are supposed to perform the CASE relearn procedure.

Hptuners software can do it, iirc.
 

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As far as the CKP circuit, all 3 wires go to the ECM.

One is a low ref (which is basically a ground, just isolated to prevent any interference, i think?), reference voltage, and the signal wire.

Should be simple to check, i hope.

Also found a post on LS1Tech from about 7 years ago that stated a certian aftermarket crank needed a counterweight chamfered away from the reluctor because it sits too close and interferes with the signal. I would think with an LS3 427 you have a 4.125" stroke crank, and the one listed is a callies 4.000"... worth checking maybe?

I dunno.
 

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Howdy, old member haven’t been on here for a while.
Back story on this car:
Bought from a member here, had to have the motor redone shortly after new cam swap. Sleeved LS3 418(417?) stroker. Had good shop do a hone on it forgot what it came out to and put it back together. Shop forgot to clean out intake that another member of shop said to clean out because there was metal in there from the failure. Car blows up on dyno. Shop made good and covered the damage. Ended up going with a 427ci since it needed to be redone anyway. So motor has been taken out twice and reinstalled at this point. Get the car back shortly after car has issues with dropping RPMs and jumping all over the place before ultimately dying. Car was unreliable to drive. Apparently was crank position sensor issue. Take to shop and have the issue diagnosed(after car sitting for a while) and fixed with new sensor. Take car home, drive here and there for a little and then same issue. Was told by shop to check the wires off the crank position sensor. Well working all the time and family life got in the way and this car was moved from spot to spot never driven but down the street and back due to the issue it was having. Would go above 3k rpms in 2nd and it would go crazy. Never really got any enjoyment out of it since the build was done and probably only a couple hundred miles on the motor. Finally found some time to take a look at this; HPT shows code being thrown of
P0336 also P0552 for speed sensor.
I have attached a picture and would like to know if the wires going to the sensor look like factory. It looks not like factory to me but wanted To see what others thought. I searched some threads on starter replacement and the code that was thrown itself to see if I could locate a picture showing the loom but I did not locate any pictures to help. Wanted to get this drivable so my wife can drive it in the summer time so any help is appreciated! Also attached the picture of the codes HPT pulled off it. View attachment 500441 View attachment 500442
That is not a factory wire harness... You need to carefully open up that wire loom to see what they did in there.
 

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With it ok for a time then not so much ok indicates something working loose probably through vibration or (looking very possible knowing the harness has been tampered with) the connection from the pigtail to the harness is not what it should be. Could be crimp on's, maybe nuts or just the leads twisted together and taped. The only exceptable means to make a connection like that is a good solder job, anything else is subject to corrosion, potential change in resistance and just screwing things up in general. Anything that interferes with the current flow in so little voltage can make a day go bad. The location of that part in the harness does not lend itself toward soldering, not even a crappy one. The reluctor is a press fit, as long as the installation is correct that is pretty low on the WTF totom pole. Something else to look at is the sensor itself; it should be gray.
 

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750WHP club :P
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Discussion Starter #12
I think that has happened. Could be bent or damaged. Misaligned, or even pressed in backwards...
If this is the case then it’s definitely installer error with the shop who did the motor as it started doing this within months of getting the car. Would make me even more irritated than I already am if this is the case. But I’m going to make sure to rule out everything else.
 

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750WHP club :P
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Discussion Starter #13
That is not a factory wire harness... You need to carefully open up that wire loom to see what they did in there.
Yeah I ended up comparing it to my other GTOs harness which I didn’t think would be easy to see from the top of the engine bay I took the tape off and could not find any issues but I cannot see the connection very well at the top when the tail goes into the rest of the harness that goes over top the bellhousing.
 

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750WHP club :P
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Discussion Starter #14
If you replace the motor or the crank sensor, you are supposed to perform the CASE relearn procedure.

Hptuners software can do it, iirc.
Luckily I have HPT pro so at least I can do the relearn on my own without taking it to a shop. I’m going to pick up some loom while I’m at work today and when I get home put the car back together and go from there. Would like to be able to have the mrs. drive it she’s gotten zero enjoyment out of it since we got it back years ago due to this reoccurring issue.
 

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750WHP club :P
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Discussion Starter #15
As far as the CKP circuit, all 3 wires go to the ECM.

One is a low ref (which is basically a ground, just isolated to prevent any interference, i think?), reference voltage, and the signal wire.

Should be simple to check, i hope.

Also found a post on LS1Tech from about 7 years ago that stated a certian aftermarket crank needed a counterweight chamfered away from the reluctor because it sits too close and interferes with the signal. I would think with an LS3 427 you have a 4.125" stroke crank, and the one listed is a callies 4.000"... worth checking maybe?

I dunno.
I’ll have to keep this in mind if this doesn’t fix the issue as I’ve never heard of that issue either until today with the signal being interferes with. Any word on if that scenario was with the 58x reluctor wheel? I’m assuming 58x since as far as I know the ls3 all had 58x. Im using 24x to keep from requiring the use of the converter box with the 58x.
 

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750WHP club :P
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Discussion Starter #16
With it ok for a time then not so much ok indicates something working loose probably through vibration or (looking very possible knowing the harness has been tampered with) the connection from the pigtail to the harness is not what it should be. Could be crimp on's, maybe nuts or just the leads twisted together and taped. The only exceptable means to make a connection like that is a good solder job, anything else is subject to corrosion, potential change in resistance and just screwing things up in general. Anything that interferes with the current flow in so little voltage can make a day go bad. The location of that part in the harness does not lend itself toward soldering, not even a crappy one. The reluctor is a press fit, as long as the installation is correct that is pretty low on the WTF totom pole. Something else to look at is the sensor itself; it should be gray.
I took the sensor out and replaced it. I recall the casing of the sensor was black but My eyes aren’t very good with shades and stuff but pretty sure it was black. I’m going to try to get a better look at the top of the harness where the factory loom was cut off on the pig tail. Possibly knife clipped the harness, with my luck I wouldn’t doubt It. Murphy’s law is in full effect.
 

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the camshaft sensor for the LS2 is grey. LS1 has the long black sensor that goes in the rear of the block by the valley.

crankshaft position sensor is listed in the post above.
 

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Discussion Starter #19

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Discussion Starter #20
Did the crank relearn over the weekend when I had some time. Appeared to have completed without issue. Plan on doing a test run to see how it drives. Even with a good drive I’m not going to consider the issue resolved until I have some good miles on it just knowing from the previous times. I really hope it’s not the reluctor moving and throwing off the sensor. If that’s the case I will at least put the situation on the table and see what the originating shop will or will not do. I would think it would be an issue with assembly since it’s been doing this throughout the entire time after some miles are put on it. I probably only have about 500 miles or so on it since it was rebuilt. The shop may have the miles documented when they had it. Hoping it doesn’t come to that and hope it’s just bad luck with the sensors.
 
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