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Discussion Starter · #1 ·
2 Big issues all the codes are showing errors and then not showing errors and then they’ll show errors again sporadically after being cleared the second big problem I’m having is oil pressure dropping while at idle After LS 2 rebuild how do I rule out ECM or PCM or fuse box failure? Or could it be both? Oil pressure also dropping when my foot is off gas not giving any throttle during test drive after the rebuild… If I’m getting the correct information on my gauges and it has in one of the codes “lost communications” with I’ve already replaced ignition replaced the power control relay and all fuses , replaced the starter relay and still both of those are coming up in my OBD reader. is there anyway to narrow down more specific problem within the OBD reader in classification and which test would that be. both are still coming up bad sporadically. do I need to get the multimeter out and how would I go about using that to trace down the wiring issue. I know this is a lot and I appreciate all inputs given any kind of experience is extremely appreciated Oh and I have installed. a high-volume melling oil pump. could it be the oil pump? Or O-ring or O-ring what is the process of elimination without Having to take the motor out or purchase more parts?

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Discussion Starter · #3 ·
That's alot to unpack.. first oil pressure, normally the "O" ring on the pickup tube gets crushed and there's the loss of pressure. I would put a mechanical oil pressure gauge and verify your pressure issue and go from there. As for codes, what codes are coming and going? Check, clean and add grounds.

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Driver 2 line 1 and my reduce power light was coming on since I have replace the ignition that hasn’t came back up but once or twice. I’ve only test driven it two different times but not for very long just down about two blocks in back to the house And as far as codes the evaporated emission is saying solenoid circuit open I think Ian on the module test I believe it is the ignition keeps failing and passing it says or is that just normal terminology? and the heater banks.. all of them are saying they failed and those are throwing the meal lamp almost every single time. I’ve checked all my connections, replaced two oxygen sensors. I do have it looks like space for four of them but I believe the guy that had the truck before me took two of them out and left them out . on my OBD reader as far as I believe volts for the O2 sensors they’re all showing 4.5 or .45 except for one is reading like .75 and my short term fuel trim is reading negative. I can send a screenshot of the data I’m looking at on the OBD reader if that will help first time using this forum so if I can send it through here and attach it I will just do that

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Discussion Starter · #5 ·
ok so multiple major issues here, right-

assuming none of the computer issues were present before the rebuild?

what modifications were present before this and what are present after the rebuild?

1-need to get ALL the codes while you still have communication with the ecm/bcm/tcm/modules.
a-B, U, P, codes, need all of them
b- reduced engine power- this could be a million things, but PROBABLY related to throttle body or MAF sensor or both
c- maybe the fuse block deal, but if nothing was happening BEFORE the remove/replace on the engine then eh

2-oil pressure
a-well, since you have consistent oil pressure, you probably have a dogbone in the back of your block, unlike someone on here a few months ago or whatever because the builder didn't install it. so that's good. it's just low, right, so ya it would be interesting to see what the mechanical gauge says at the oil pressure sensor port and the port on the block behind the power steering pump, but that's a pain to get to. I don't remember what the minimum spec on oil pressure is, but the computer will send the truck into reduced power mode if oil pressure drops too low. I'm not saying this is it, I'm saying this will do it.
b- ya could be the o ring, absolutely. I'm not an engine builder, but I do know bearings and clearances are taken into account when building an engine, a stockish rebuild should be compatible with damn near anything out there, you can put 5w30 in it, 10w 40, whatever, it should be fine. obviously people get wrapped around the axle on oil weights and this and that, but its a gen 4 gm engine. it will eat what you throw at it, designed to eat 5w30 from the factory. You should see 20-30 at hot idle and 40-50 at higher rpms.

3- oxygen sensors
a- this isn't that big of a deal right now, but it would be good to check out the tune to see what, if any changes were made by a previous owner/tuner/shop/whatever.
b-these not working aren't that big of a deal right now, imo

As far as the wiring, ya a general continuity check on every wire would be good... make sure nothing is shorted to ground that isn't supposed to be. Make sure you have contiuity from the connector at the ecm to each sensor connector pin. The forum has great schematics in the electrical section, i think. Ya these intermittent things are a pain. Start with the electrical/wiring, two cents. this is my opinion

View attachment 104460
I took it on another test drive and this test drive a lot longer because seeing all these codes were only from running it idle in my driveway and the fuse box being out for almost a year I wanted to make sure these problems didn't just go away after warming it up and driving a bit. I also put dielectric grease but def have some fuse problems because when I barely tap the power control module relay the fuel pump will not come on. When I tighten the bolts to the fuse box all the way down I noticed out of desperation trying to get the brand new ignition to work when I back the bolts off the ignition worked again and fuel pump came back on. Its got to be an issue with fuse box to some degree right? I have all the freeze frame data - how should I send that over to take a look? Thanks for the advice. I can send email, DM, text here etc. Really appreciate all the feedback. I'm just going back over things time after time. I'm going to replace the oil pressure sender just because and should there be any oil leaking from the torque converter transmission housing or does the rear main seal obviously block that from happening so the torque is internally oiled from the transmission? The other issue is that I did accidently pinch my fuel lines and only was able to recover 1 of the 3/8 lines and the evaporative commission control return hose ended up using one from Silverado which i think was a 7/16. I just replaced both of those today so the correct sized fuel lines are going back on the truck today. The main reoccurring code was evaporative commissions solenoid circuit open and misfire and driver 1 line 2 and it is telling me it's loosing communications with the body control module etc. etc. but it would be easier if I sent you the data like you said.
As far as modifications go before the 1st rebuild I spun a rod bearing and the only change was the bent rod, the crank and the rod bearings and the cam. Installed a Stage 2 cam. However I never actually got it tuned because the builder at the time unfortunately didn't turn out to be legit. Now fast forward 9 months after getting it back I spun another rod bearing and my oil pressure was consistently around 40 psi. The day that I spun the bearing it only dropped to about 35 psi and was still running but I turned it off as soon as I heard it happen. That is why this time I took it upon myself to do the rebuild and acquire this exp. and knowledge for myself due to the previous experience. Next as far as the new mods that I installed are as follows:
1. crank
2. rod bearings
3. honed cylinders
4. had the block machined and decked
5. I personally ported and polished my heads
6. replaced the valve stem seals (this is the first ? in my mind. I didn't find out until after installing heads that there are different size valve stem seals between the intake and exhaust but the BTR cam that I got came with the valve stems seals, cam and springs; I did read in my hanes guide that if they were mixed up or installed exhaust valve seals on intake side or if wasn't correct could be a result in loss in oil pressure but the BTR cam for my truck specifically came with all the same, I thought, valve stem seals. all the same color...)
7. Also inside the block had new cam bearings installed when at machine shop.
8. New rear main seal
9. New timing chain
10. New timing chain guide
11. New Melling high volume oil pump
12. Also when ported the heads I lapped all the valves very generously but that just made them seat smoother
13. I welded a baffle plate in the oil pan and left about a 1 inch long from deflector tray to the bottom of oil pan doorway for the oil to go in and out of but where the pick up tube is is basically enclosed 3/4 of the way up inside the oil pan obviously to keep the pick up tube submerged and not have to rebuild my motor again a 3rd year in a row
16. it was an all wheel drive and that was the issue the front sump oil pick up in the front of the pan so any kind of acceleration the pick up tube would starve for oil then there goes the rod bearing. So bad call bad flaw not sure but. I took the front drive shaft and front differential out and transfer case that was originally in it came out. I replaced transfer case with a 4 wheel drive electric selectable transfer case and stuck it in 2 wheel drive and installed it. This was before the last spun rod bearing before my personal rebuild here.
15. Replaced battery
16. replaced all fuses
17. Still have an electric fan and oil puller to install
18. Still have my Melling high pressure oil pump from the previous build so if it does turn out to be a bad oil pump after taking your advice checking sender unit etc. going to do what I can to NOT have to take harmonic balancer off because my installer stripped when I was installing it.
- Only other possibility I can think of is one of the long bolts of the 2 bolts oil pan rear main seal stripped. I was able to get 85% of bolt out and stuck another bolt in there but it didn't feel as secure as original so I guess now I will have to tap that and finally learn how to do that because I know that bolt is extremely important which could be a part of the oil pressure issue BUT my rear main seal has 13 other bolts in it so at the same time, and it has all new gaskets, I just didn't think at first it could cause too many problems but maybe it did..???...
---upon starting it the first major difference is that it sounds like it has a stage 4 cam from the more mild stage 2 cam that is actually in this and you will see this in the freeze frame data or pictures of live data I can send you showing ignition timing going all the way up to 34 within a second is all the way back down to 7. I know there are guys putting ghost cams on their trucks by messing with the timing and almost the exact same form to make it sound like it has a cam but for whatever reason my truck is doing it and exaggerating the cam I already have installed in it. It sounds rowdy and awesome but I know it's not correct.
I know some of these issues will be resolved with the tuner but until I get some of the main issues fixed I can't get it tuned bc dyno guy said I could not have any misfires or oil pressure issues in order to put it on the dyno and tune it.
Let me know where to send the freeze frame data and any other code information info I have. Man I will send you gift card for helping me out or something whatever you want. This is a lot I know but my livelihood depends on getting this rebuild done!
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