P0403 on '99 Chrysler Voyager resets after 100 miles...

Hello A friend recently bought a '99 Voyager about 150,000 3.3L engine. The SES light was on and I scanned the system and found P0401 and P0403 codes. I removed the EGR valve and checked it with a vacuum pump. It seemed to function properly and held open as long as vacuum was held. Released vacuum and the valve released.

I investigated and found that one of the two pins on the connector that connects to the EGR control solenoid valve had corroded away. I changed the connector and control valve (picked up a few used control valves from a salvage yard a friend owns), disconnected the negative cable for a while to reset the codes and figured that would cure it.

My friend said about 5 days later (about half a tank of fuel or 100 miles) the light came on again. I scanned again and it's code P0403 again. I had an extra control valve so I figured what the heck it's free and easy to change maybe the control valve I had put in was bad. So I swapped in the 2nd used control valve, disconnected the negative cable and away he went.

Well after another half tank of gas about the same amount of time the light came on again.

What stumps me is why does it take so long (100 miles or more, about a weeks worth of driving for him) for the SES light to come on??

Any ideas would be much appreciated thanks!

Well after searching the forum I have found that the wiring (especially where the wires pass by the bellhousing) tend to be troublesome on these voyagers. I'll check for batt voltage/continuity at ECU pin #40 at the EGR control solenoid and see what I find.

One question - where is the PCM for a '99 Caravan? I know I should have a factory manual and I do for each of my own 4 cars but this is a van that belongs to a 79 year old co-worker of my wife's on a very fixed income (hence the reason I am working on it). If anyone could tell me where the PCM is on this Voyager it would be appreciated thanks!