99 Suburban intermittant start problem

My Suburban has 147k miles on it and has functioned flawlessly for as long as I've owned it. 3 months ago while leaving work and after a long steady rain it would not start. It would run momentarily (1/2 to 1 second) and die. Had it towed to a reputable repair shop that night. Next morning I stopped by (just to see) and it started. The shop replaced fuel filter and checked fuel pump pressure which tested OK. Codes he got were for O2 (which I knew about) and a security code. 3 months later I'm still having the problem. Seems to occur after a soaking rain or when humidity is exceptionally high. I can usually let it sit for a while and it will start just fine. Any thoughts on where I might look for problems?

I experienced (experience) a similar problem only during the winter months. the problem is with the security system. Either the sensor or the module is bad(sometimes) in my case. The solution is to leave the key in the "on" position for I think 10 minutes. At that point the computer will reset the password, and after shutting off the vehicle, it will restart. Frustrating problem. Hope this gives you something to rule out at least.

I will give this a try and see what happens. It's so inconsistant that you never know when it's going to fail. Thanks for the info.

I had the same deal... just hit and miss. Have the security sensors been replaced? Mine were changed and the problem still occurred. My '99 TD burb was also starting really rough when it first started in the morning. Through some research i found that my PMD (pump mounted driver) was bad. I changed that and relocated it.... the starting problem mysteriously went away and it cold starts no problem at all.

I have not had the security sensors replaced but I'm convinced that's the problem. It happened again about two weeks ago. This time I paid particular attention to the "Security" idiot light. It did not go out after the ignition switch was left in the ON position for several minutes. That evening, after leaving the burb sit all afternoon, I turned the switch to ON, the idiot light went out after a few seconds, and poof, it started.

Well here's a little update on what i thought was a solved problem.. I changed the PMD a week ago and all seemed well until this morning.... once again the burb decided not to start.. AAARRGG!!!! Fortunately, it was at a GM dealer getting some other service work done when it occurred so my mechanic did a full diagnostic and found that the Theft Deterrent Module wasn't sending or receiving information with the main computer. He changed that out (about $160) and wha-la, no more trouble codes. Hopefully we got it this time. It would've been cool if we could have just bypassed all that theft deterrent crap.... but i guess if we could, so could a thief. I keep ya posted..... Oh BTW the PMD i changed.. it did fix my non-functioning cruise control, the cold starting problem, and the occasional "bucking" it did on the expressway....