03 LB7 won't start (DTC 0335), need advice.

[Claven]

Here is what happened, went to a friends place last week, everything was fine, when I went to leave, I wanted to warm my truck up, turned the key and it just cranked over without starting. Code I got was 0335, which is crankshaft position sensor no signal, I replaced the sensor, that didn't do it, so I checked the voltage at the sensor plug with my meter and it checked out OK (except where it says I should get battery voltage, I was getting 11 volts, is that normal?) , I unplugged the wires from the ECM to check for corrosion and found nothing, then I checked the reluctor wheel and it feels tight, so I thought maybe I would try disconnecting and reconnecting the batteries just to see if that would do anything...now it wont even crank over. Any ideas? today I was going to remove CKP signal wire from the ECM to see if there is a signal there, but it wont crank over, I get lights and all that, so it's not the battery connection. I do have all the service manuals, but this last problem threw me for a loop, I need some pointers as to where I should start now.

[DmaxMaverick]

If all the connections, grounds, voltages, and duty cycle check out, the only thing left is the ECM. The voltage minimum is 10V, and the duty cycle should be 40-55%. If you have steady continuity between the CPK connector and the ECM, and you are showing the specified duty cycle and voltages, it may be time for an ECM. I went through the diagnostics, and that's the bottom line. The only other mention is crankshaft end play, which could cause the CPK/reluctor gap to fluctuate. But if that's the cause, you should be having other issues, too.

I suggest this...
Check your batteries, cables and grounds. If you still have the OEM batteries, one/both could be failing, and the result is all kinds of electronical issues, including a no-start, and DTC P0335, among other possible codes. Verify good batteries and connections. Disconnect both battery grounds and check voltage at the batteries. If either is less than ~12.6V, or there is a differential between them more than ~.5V, it could be a simple as that. If either battery is cracked or leaking near the terminals, that could be an indicator, as well.

Good luck with this and keep us posted on your progress.

[Claven]

Well...thats the track I was on, however, it started. What I did was when I got there I hooked up the booster cables and charged the batteries up before anything, then I disconnected the performance module (which i already tried once, with no luck), and then I reset the ECM "back to stock"(which I hadn't tried), turned the key and it started. So the way I see it, it must be one of three things: the performance module, the connectors for it, or the ECM software glitched somehow (bad ECM as you suggested). I will try putting it all back on and see what I can find, and I'll keep you posted. I really appreciate the quick response and knowledgeable answer, I figured I was on the right track, but it's nice to have some experienced backup when going in. Thanks again.

[Mark Rinker]

Interesting thread. Keep us posted, please. With my Dmax's running coast to coast, having these threads handy will unfortunately come in handy as they age.

No performance boxes is my current thought, to keep things simple. Plan to run custom tunes on the ECMs instead.

[Claven]

Well...I got my truck into the shop today, finally out of the cold, its been in the low minus 30's for about a week now, the "no crank" issue came back a couple times and what I found was I forgot to tighten the starter bolts and it was loosing it's ground (did the front tranny seal 2 weeks ago, don't worry I already kicked myself), as for the "crank with no start", it was the horsepower module connectors, I found a significant amount of corrosion on some of the pins, as soon as I plug it in, it wont start. I haven't repaired the module yet, but I'm 100% sure that's what it is. So there's my results, thanks again for the help, it was really appreciated.