I just built a 98 ls1 put ms4 cam, cncd heads, forged bottom end, lt headers, fast 102 intake with nick williams 102 tb, underdrive crank pulley and nitrous.

Here is the senario. Initial start up was great first key turn aand it sounded like a mean cammed ls1. I had my tuner come to tune car. Started to crank and got some nasty backfires. Once it started it didn't sound like a cammed car anymore? Wtf now I have a p0340 high voltage code replaced sensor still there.

I am at my wits end on this car I pulled front cover to double check timing it's dead on dot to dot. What I failed to check is if the cam had come loose but it looked normal. What do I do? I have hp tuner now but little new at using it. Of failed to mention I did check push rods and they are fine.

PLEASE HELP!

 

Additionally I have checked all wiring there is no problem.

 

1st step is you need to check all your grounds. Expecially the ones on back the driver head.

If loose they can cause several problems

 

Grounds are secure for sure I put harness on while body was off.

 

wow no help thats crazy i have read all posts and nothing sounds like my problem.

 

If you disconnect the battery for a little while and reconnect does it start better? My car actually used to do the opposite, first start after a battery disconnect and it would idle like crap, but shut it off and turn it back on immediately and it would be perfect. I think the first startup is like an idle relearn mode so it will run differently.

Also in regards to you saying it "didn't sound cammed", since its not tuned your A/F at idle may be way off, and that can make a huge difference in how it sounds at idle. My first startup after H/C sounded almost stock even open headers, but once I got the A/F nailed and the idle to settle a little bit more she started sounding much better

 

to answer your question yes i have disconnected battery and no change it still throws p0340 high voltage cam sensor. i am stumped from all the threads i have read my only option is to open her up. The first 10 start ups it sounded like a ms4 cam mean as hell. Now i have added the offroad y pipe and it sounds like a stock motor. The tuner that was referred to me tried tuning and could not keep it running brought the cam sound back but would not run. He said i would have to fix the cam code first then tune it on wide band for speed density. i got frustrated cause i have poored thousands of dollars on the best parts money can buy and it still isnt running right. Can it be tuned with that cam code?

 

The camshaft position sensor circuit is relatively simple in that the sensor connects only to the PCM which provides a 12 volt reference, a low reference and signal circuit. Since you have already replaced the sensor the problem lies in the connector to the sensor, the wiring harness to the PCM, the PCM connection or the PCM itself. The harness can also have intermittent issues if the harness is too close to other electronics. Finally, the PCM must be adequately grounded, but if it were not you would likely be getting some other codes.

 

I agree with you completely i have tested all connections from pcm to sensor and all checks out fine. All my grounds are tight and the few codes its throwing are untuned problems accept the cam code. This is really throwing me for a loop all the corvette forums have cam walking problems. I was hoping to find a wiring issue believe me. I can not get rid of the code it comes back as soon as i remove it. ill tear it down tomm intake and valley cover and see what happens.

 

As far as being close to other electronics the car is gutted this is a trck car only no ac or radio.

 

did you do a gen4 timing cover/sensor swap also?

 

i did not do a timing cover swap everything is the same. I was Wrong on the code its p0343 sorry for the mistake maybe this will clear things up

 

ok keeping my fingers crossed but the part number off of the cam sensor is for a 99 and dealer says the 98 part number is specific to 98 so i ordered that 118 dollar cam sensor and will be here in the morning. Anybody know if that would make a difference? The difference between 98 and 99 cam sensor?

 

P0340 and P0343 are essentially the same. In addition to the conditions I posted earlier, the literature on P0343 lists other possible causes as: (1) sensor contact with the reluctor ring; and/or (2) foreign material passing between sensor and reluctor ring.

 

but the real question is are the 99 and 98 sensors different? i have checked reluctor ring on cam and it is clean. The bottom of the sensor doesnt have any contact marks or rub marks that show contact at all.

 

They may be different. Rock Auto list GM#12260229 Delco#213355 for 1998, but GM#12561211 Delco#213363 for 1999.

 

well i believe since the 98 is such a difference in pcm tuning than the 99 i have the wrong sensor in it. I have it ordered though the dealer so tomm i will know for sure. Thanks for all your help i will post updates tomm.

 

Did you have the alternator wired in when you started it?

 

everything was pre wired before i put body back on. put new sensor in today and have the same problem. switched to a different computer from my parts car same code wtf

 

You say the fault won't clear and returns immediately? (hard fault) That sounds like an open or shorted wire between ecm and sensor. Use a DVM with audible function, disconnect sensor and disconnect ecm and see if there is continuity to ground at any of the power (12v) or reference (5v) pin connectors then check them connector to connector to see if any of the 3 are open.