4.7L PCM can't ignore the PS switch. 4.7L wiring harness always has a connector for the PS switch, IIRC it splits out of the big harness at the base of the branch that goes to the engine-oil-pressure sensor.

I'd assume this vehicle would have always been popping a code if the switch wasn't there.. unless it was never driven over 40MPH.

 

I have owned this truck for the past three years with out any issues or codes.This problem started when I replaced the 2nd pcm. The first replacement put up an evap code .The shop checked out the purge solenoid and it was fine. I sent that pcm back to the rebuilder and the following TWO pcm's show the po551 code after about 20 miles or so. The local shop reflashed the pcm with my mvn and still the po551 code.I have had the truck checked out by my ASE mechanic and myself and there isn't any wires for this .Unfortunately, I cannot acquire my original PCM as it has been rebuilt. The next plan is too open the harness and chase down the wire from the pcm and see where it leads too.Due to a recent surgery, I will have to have the shop do it to the tune of $300-$400 !! Have you any more ideas ? Thanks

 

what is your build date (the MDH code on your door sticker)?

I don't see any evidence that 03 4.7's were ever built without the switch, but 04 4.7's do NOT have the switch.

 

I will have to wait until Monday when the shop opens to check it out. I do know the original PCM was dated 23/06/2003.

 

I checked my vin and it all checks out as to the year,engine,ect. The last six digits are:618649 which is supposed to be the build sequence number ?

 

Manufacture date is 6/03

 

hm.. my '03 was 594678.. it definitely had the switch..

Do you have a buildsheet for your rig?

 

No I don't...I bought this used from a lot in IN. three years ago.It has never shown any codes prior to this other than an evap code do to a loose gas cap. This has been a real headache...What we are going to try is to ground the wire that would go to the switch from the pcm.It is a blue/orange wire from pin 31.Hopefully, the pcm will accept this as a completed circuit and will stop showing the error code and thus stop the engine low idle stall.

 

reading the description of the OBD code in the diagnostic manual, I have my doubts that will fool the PCM.

If you have that wire in your harness, then you should have the switch connector as well; I don't think they'd put in a wire to nowhere..

It is PCM connector C3 pin 30, and also pin 10 in C105 near the PCM (that will be the easier place to get at it)

...tom

 

I have looked again for the wire hookup and it isn't there. My pcm has four connections;could that be why it doesn't have a switch in line ? Thanks for the information ....backroadsltd

 

sorry, clipped you the wrong C105 location drawing.

All 2003 4.7L's have a 4-connector PCM. You should have the wire.. Check C105 to see if it has a dark-blue/orange wire in pin 10..

 

Thanks for all your help !! Although I hated to do it this way, my Durango is back on the road after two months of chasing my tail. I found the wire, cut it ,then grounded it to the firewall. It's been over 50 miles with out the check engine light and she drives fine. Hopefully, I haven't created any long range issues.....

 

I just wonder where the wire goes.. I can't believe there would be a wire that doesn't at least end up in a disconnected connector..

If you make it to some get-together that I'm also at, ping me and I'll bring a tone-tracker to see if we can figure out where it goes..

The PCM test happens after driving above 40MPH for some amount of time (I forget how long, 30sec I think) .. so drive a bit on the highway to make sure it behaves..


...tom