I had a "Service Engine Soon light" come on with my 2001 Pathfinder, even though the vehicle seemed to be running fine. I took it to Autozone and they read the code as P1140, and it stated that I had a "water in fuel condition." I was perplexed by that, and they said it could be that I got some bad gas and sold me a bottle of fuel additive to remove any excess water from my system. I added the fuel additive, they cleared the code, but as soon as I cranked up again about 2 hours later the SES light was back on.
I decided to err on the side of caution so I took my vehicle into the Nissan dealer, who diagnosed that I had a bad VTC sensor on the right bank. They said it had something to do with valve timing control, or something like that. It took them no more than an hour to fix it, and the dealer charged me $353. Let me tell ya, that is one painful repair bill considering the vehicle was running fine when I took it in. The service guy told me, however, that there was a chance of causing engine damage if I continued to run it that way and the engine had a knock or misfire.
I'm not enough of a mechanic to determine if he was shooting straight, or selling me a line (for $353)!!!!