need help on my first LS conversion,04 LQ9 in an 86 K5, no start

My computer has been reflashed and VATS removed. I have good fuel pressure and plugs are wet. I have random and weak fire only on 4 and 6. I have checked pinouts over and over and grounds but do not have 12v supply voltage to the crank sensor if I measure right at the pcm at key on with sensor disconnected. With it connected, I get .5 volts with the key on and off. Fuel pump signal is good to relay and injectors are firing. I can connect a code reader and it communicates and shows all monitors ready to learn. Bad PCM?

thanks

Have you tried replacing both with a known good crank and cam sensor? Are you certain you did not pinch part of the wiring harness between the engine and transmission during the install? Don't ask me how I know to check for this. :whack:

I did check harness routing and I ohmed out all 3 wires from the pcm connector to the crank sensor and they checked good. I have not tried another sensor. Are you saying I might not get the 12v without a good sensor in the circuit?

thanks

pull the connector off the pcm, find the three wires that go to the crank and cam sensors, ohm them out to ground and see if you have a short to ground somewhere.

ok, I'll check them tomorrow

Correct me if im wrong but if you had no crank signal, you would also have no injector pulse. Also you would have no spark at all. If your scan tool displays any data, look at engine rpm during cranking. Kinda sounds more like harness issues than a lack of ckp signal.

Subscribed, im curious.

Did you build or buy your harness? Which pcm?

Thanks for the replys. Just finished checking out crank and cam sensor wiring. No shorts to ground or each other but mysteriously I now have 11.6 or so volts to crank and cam sensors. I'm going to put pcm connector back together and try it again before I buy new sensors. Will be tomorrow before I can get back to it.

I modified an 04 escalade harness per the "pinout" sticky, btw, thanks RedHeartBeat. PCM is 12576106 with Hwd. No. 12570558. I'm using this one because the only trans I had was a 700r4 and wanted to use dbc instead of dbw.

If crank sensor was bad, I wouldn't see rpm on scan tool, right?

Thanks for your help

hey steve iam new to this site: iam not a senior member but i know a bit about automotive u are not to have 12v at any sensor they run on a 5 volt reference voltage to ck for an open ohm out the wire it should read 2 ohms but if on two cylinder u are getting fuel fouled plugs i think ur issue would more likely be stuck open injectors just remove fuel rail make sure injectors are secured on fuel rail with thier locks cycle key dont crank and see which one leaks

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Originally Posted by stevebbc

Thanks for the replys. Just finished checking out crank and cam sensor wiring. No shorts to ground or each other but mysteriously I now have 11.6 or so volts to crank and cam sensors. I'm going to put pcm connector back together and try it again before I buy new sensors. Will be tomorrow before I can get back to it.

I modified an 04 escalade harness per the "pinout" sticky, btw, thanks RedHeartBeat. PCM is 12576106 with Hwd. No. 12570558. I'm using this one because the only trans I had was a 700r4 and wanted to use dbc instead of dbw.

If crank sensor was bad, I wouldn't see rpm on scan tool, right?

Thanks for your help

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That's correct, if the ckp signal is missing, weather it be due to faulty sensor or wiring, you will see no rpm during cranking while monitoring an engine speed pid. I would certainly check that before buying anything if you're able. Good luck, ill keep checking in.

Tried it again today after putting connector and old sensor back in. Still no start. Ocassional firing with valves still open, back thru throttle body.

So what is sensor supply voltage supposed to be. All the schematics I see of the crank and cam sensor say 12v ref.

Going to try new crank and cam sensor unless somebody's got another idea.

thanks

Try a noid light on the fuel injectors and see if they're firing. They could be stuck if the engine sat any length of time in the bone yard.

I got a loaner set of lights today from AutoZone but none of them are the right size. I'll try Advance or Oreilly's.

Just another piece of info, I have pulled off injector connectors and put voltage to 4 or 5 of them and all have the solenoid clicking if I just quickly touch the negative. So I think injectors are good and not sticking. I've built 7 or 8 motors and tuned a bunch more. (old school)This is a classic timing issue. Backfiring thru the intake and starter is struggling to turn it over.

Thanks

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Originally Posted by stevebbc

Just another piece of info, I have pulled off injector connectors and put voltage to 4 or 5 of them and all have the solenoid clicking if I just quickly touch the negative. So I think injectors are good and not sticking. I've built 7 or 8 motors and tuned a bunch more. (old school)This is a classic timing issue. Backfiring thru the intake and starter is struggling to turn it over.

Thanks

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Hmmmm. Strange. You can use any noid light. Just make a couple small jumper wires to attach the pins on the light to the pins in the inj connector. If you think its a timing issue, there would have to be coil control wires crossed up. Im really curious now. I had a cmp connector pinned wrong once and it took forever to start the engine, all the while backfiring. That sounds very similar to your troubles. I doubt you have a ckp problem because you have some spark and fuel. Cmp on the other hand is looking more and more suspect. Keep at it. It'll be worth it.

Just put in new crank sensor and its very close to firing up. What is a crank sensor learn procedure? Is it necessary for a start? or does it just improve performance?

thanks guys!

I believe it is needed if the pcm is setting false misfire dtcs. Engine must be running to relearn.

stupid question, I do not have the oil presure sensor connected to the pcm cause I'm gonna use an adapter and use original gage on the dash. The pcm wouldn't keep it from starting if it didn't see the pressure sender signal would it?

No, I don't use it in any swaps

Maybe I better go back to square one. While checking wiring yesterday, I started wondering about some basic things I could have got wrong like:
Is the picture of the connector in the "Pinout" sticky the pcm or the wire harness connector?
If its the wire harness connector, which side are you looking at, the front or the back?
On the pcm, which is c1, the top or the bottom?

thanks

You may be on to something here. The blue connector is C1. The pcm should say blue where the blue connector goes. Be sure you are not using a late (blue/green) diagram with an early (red/blue) pcm or Vise versa. The connector "view" shouldn't really matter because you are just using the cavity numbers on the connectors themselves. Also looking at the connector cavity numbers, one connector will hook in the pcm one direction and the other goes the other direction.

I like your idea of retracing your steps and I feel like you may possibly find the culprit this way.

If I understand correctly, early is 99-02 and late is 03+. Im still a little unclear about weather or not a blue green pcm can be used with dbc or if a red blue pcm can be used with dbw. Don't use the pinouts here as a view, but rather just for the cavity numbers, that way there will be no confusion about weather you are looking at the front or backside of the coonector.

ok, installed new cam sensor and crank sensor. Have ignition all the way around now. Injectors are lighting Noid light. Still no crank. My programmer specified this pcm pn from an 03 with blue/green connector. I've been over the wiring and cannot find anything wrong but check me out anyway. Pin #'s in circles are in place, all others have been removed. I'm going by the pin #'s on the back of the aluminum connector housing. No. 1 is in the top LH corner. I see the way the connectors are keyed so one goes in opposite from the other and the pcm is marked blue and green. Gonna take fuel rails adn injectors off and clean next.Attachment 4940Attachment 4939Attachment 4938Attachment 4937Attachment 4936

I don't necessarily see anything wrong, although I am a little confused about some of your written in wires. Maybe a veteran will see the culprit.

You may be way ahead of me here but don't take offense. There are many duplicate wires throughout the harness. Did you check continuity on the duplicates to make sure non of them were mixed up?

At this point I bet its something you have "assumed" is right all along. Think about everything you have physically checked and what you have not. Physically check what you have not.

Also at this point, its time to monitor an engine speed pid. That will be an excellent starting point. If the pcm sees engine rpm, and displays it on a scan tool, then there is no doubt that the pcm has everything it needs to start the engine.

There has got to be some mix up with pcm pinning. I think the diagrams you are using are for a red blue pcm, although I am quite certain that all circuits required to run the engine are the same.

Where are you located?

hey steve are the shematics u have are from like gm work shop manual ? normally all sensors run on a 5 volt ref , but if u say u r shematic says 12v and on ur previous thread u said u had no voltage on the pwr for the crank sensor and then u did load test that circuit with a fog lamp bulb u could have high resistance, have u already ckd for fuel pressure or spark are all the plugs wet or only 4and 6 did u ck with noide light if injector signal ill try and get a shematic from work tomorrow and see if it says 12v like urs on crank sensor

n-guerra, I replaced crank and cam sensor, now have 12v at sensors. Schematics are from links on this site and they are complete GM schematics for 03 Silverado 3500, in color even. I'm using this in conjunction with chart on LT1 Swap site on what wires to remove for a harness to run the motor only. Now could the positive 12v be knocked down to 5 by a -5v low ref out of the pcm? If so, then maybe u r on to something. Maybe this feature in the pcm is not working. I still have the 04 Escalade pcm with factory programming. Would it hurt anything to connect this one just to see if it would run it for a few seconds. I know the vats would turn it off.

I have fire all the way round now and noid is lighting on all injectors. Took fuel rail and injectors off last nite and tapped them with 12v. All were spraying plenty of fuel that was still in the rails.

Vortecyota - I'm in eastern N. Carolina. at least for now, if my wife doesn't kick me out

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Originally Posted by n-guerra

hey steve iam new to this site: iam not a senior member but i know a bit about automotive u are not to have 12v at any sensor they run on a 5 volt reference voltage to ck for an open ohm out the wire it should read 2 ohms but if on two cylinder u are getting fuel fouled plugs i think ur issue would more likely be stuck open injectors just remove fuel rail make sure injectors are secured on fuel rail with thier locks cycle key dont crank and see which one leaks

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No, the CKP and the MAF for TWO are 12v.

To the OP, those connector end views are with the terminal ends facing you, not looking at them where the wire go in as in the pics. Look closely at the aluminum body of the connectors and you'll see the numbers.

I just now read this topic so forgive me but you're using a red and blue PCM like you should for this swap, right? At least it makes more sense to me for a DBC swap.

If the plugs are wet, the injectors are doing something...most likely at the wrong time. A noid won't help injector timing issues. Does it have spark for sure?

Ordered new pcm(411) and tune from a highly recommended tuner. Installed pcm, same problem, no start, occassional pop and misfire thru tb. Had spark and injectors were lighting noid light. I was told to do the "30 minute learn" procedure. Did the procedure and now have spark but injectors are not firing. I have a call into the tuner but haven't heard back yet. Anybody seen this before or know what's going on here?

This is crazy. I wish you were close to me. I wanna see it. Never heard of the 30 min learn procedure. Injector timing is not critical to startup, ignition however, is. I know you know that, but. Gotta be cmp/ wiring, or coil wiring. Ckp is working because you do have spark and did have fuel. Move closer to me so I can figure it out. Lol

On a serious note, if you get desperate enough, haul that dude down here to Atl and we will figure this out.

Vortecyota, 30 min procedure is turn key to crank, then to on and let stay on 10 minutes, turn key to off, wait 5 seconds, then do this 2 more times. Sounds like something to do with VATS to me. Anyway it killed the injectors.

I've been looking at my fuse block set up. I have one relay turned on by the keyswitch and it supplies power to the fuse block. Another relay running the fuel pump. When I'm cranking, the voltage at the fuse block drops from 12.5 to 10.5v. I get the same drop measuring straight off the battery. Seems like this should be sufficient to keep everything live while cranking. I get a good strong spark at the spark tester, you can hear it arcing.

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Originally Posted by vortecyota

Never heard of the 30 min learn procedure.

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Wow. I guess that means you use TIS2WEB on a GM account or with on the client server with a yearly subscription.

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Originally Posted by GasGuzzler

Wow. I guess that means you use TIS2WEB on a GM account or with on the client server with a yearly subscription.

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I had a brain fart. Lol. That procedure is for the pcm to learn the fuel enable passkey and the op had inj pulse so I never considered that procedure.

Im just a trans builder and we don't reflash so no I have never used TIS2WEB. When necessary, we have a mobile guy come out. Service all makes and models so we are not interested in setting up to update cals for thousands of different vehicles. We already have plenty to stay current with.

Op- im sure your tuner disabled VATS but since you did the relearn, I wonder if that could have in effect re enabled it??? Never heard of anyone trying a relearn with VATS disabled.

We got your message, i double checked your file and vats is definitely turned off.

I'm not sure if there's anything else you needed to go over, but from the looks of it, you have a lot of help from the guys here, vs one on the phone.
It could be anything and to go over each detail on the phone with one tech vs having 5 minds going at it...

Keep posting and we'll do our best to reply with answers,
thanks,
allen

Allen, have you ever known of anyone to do a passlock relearn after VATS has been set to none? Its just odd that he had noid pulse before the relearn but not after.

Steve, now that you have no inj pulse, check for key on 12v on the pink inj wires.

you can perform the procedure, but i don't see it doing any good or change. vats is off, so it wouldn't make a difference. sounds like some sort of intermittent issue if things are changing.

i had the same issue regarding ignition crank voltage on my truck, but my truck would turn over a few times, then finally start on the 2-4 try.
my truck didn't have crank voltage going to the relay/fuse, etc. that was an ignition issue tho.

make sure all the sensors are reading correctly, make sure the crank is producing an rpm, cam sensor is toggling, map is 100kpa during crank, injectors are opening or at least commanded, can't remember the pulse value, but maybe like 10ms or so, be sure the pcm is grounded, be sure the pcm has it's battery and ignition voltage, and keeps voltage while cranking. 10volts is fine.


might wannatry this first, take all your ignition wires straight to battery, see if it starts. doing this you'll bypass the ignition ON and ignition crank voltage for now.
NOTE: engine will stay running when key is turned OFF.

I still have 12.25v on the pink wires to the injectors during crank and in the run postion. To me, this means the pcm is not setting the ground to energize the injector coils. This pcm was firing the injectors before I did the learn procedure, but not afterwards. How can I undo the learn procedure?

If I get time tomorrow, I'm going to try the previous pcm.

Thanks for the replys and suggestions, keep'm comin!

This is what has me curious about what happens when a relearn is done on a pcm that has vats disabled. Im with Allen. I wouldn't think it would change a thing, but you are the first guy I've known of to do it and now the pcm is not pulsing the injectors.

Your other pcm hasent had vats disabled has it?

Either way, if you have 12v to the injectors, a Ckp signal and obviosly the injectors are wired right bc you had pulse before, I think you need to have NP look at your tun file to see if somehow the relearn reenabled vats. I don't think that's possible, but I think this is the first time many or all of us have heard of someone doing a relearn after vats disable. I am looking forward to a conclusion to this story!

If it comes down to it, my offer still stands. Im sure I could find the culprit if I was with the truck.

The other pcm is a stand alone too and has had the vats disabled but no learn procedure. Both had the same symptoms up until I did the learn.

Get a handheld diagnostic tool and read the codes that are coming up. You have to have codes if it's not starting. Have you checked all the grounds to make sure none of the ground wires a broken internally? Are they all grounded to either the driver side backside of the head, the driver side of the block down by the oil pan towards the front of the engine and the one ground that goes on the passenger side of the engine centerline, top of the block just a few inches away from the oil pressure sensor. A good source for the handheld diagnostic tool is Oreilly's where they actually rent it, take it home and use it.