2001 Pathfinder - solenoid problem

[gumby6]

My engine light has come on many times over the years and have had parts replaced each time. It just went on again while on a road trip last month so had no choice but to have it repaired at the dealer. Now I'm looking at my previous bills and this forum and it sounds like I've been mis-diagnosed... Can you please tell me if I could have an other "under-lying" problem here... I've spent a small fortune on this...

Here is a summary of what's been done so far....July 2005replaced 23731-2Y524 (96.69 cdn$)

July 2006replaced 23796-4W000 ($250.34 cdn$)replaced 23731-2Y524 (free as last one was just under 12 mths old)

March 2007replaced 23796-4W005 ($246.00us$) what's the difference between this part and the 4W000?

Any help / information would be greatly appreciated..

Thanks.