I'm catching a P0603 from my 02 7.3L. I have a tuner, and I know that it is a relatively common code if you have a tuner. However, I put the stock tune back on the truck, cleared the DTCs, and ran it for a couple of days, checked the codes again without changing the tune, and the 0603 is there again. What does this indicate, and what symptoms can it cause? Is my PCM bad? Checked fuse 36 good, BTW. Truck doesn't seem to have the throttle response it used to and I've been fooling with it off and on for a couple of months. Advice or opinions much appreciated!

 

The P0603 means the PCM lost power. Will set whenever the batts are disconnected or a PCM fuse is removed or blown or if there is a flakey contact in the PCM power relay. Swap the IDM and PCM power relays and remove and reseat the fuses. Clear it and then wait and see if it comes back.

Fuse 22 is for the PCM power- it's designated "Engine Control"

Fuse 36 is just for the KAM - Keep Alive Memory in he PCM

Relay 302 is PCM power - Designated Powertrain (EEC) Relay

Relay 303 is IDM power

Just having the 0603 code set should not cause any performance symptoms.

You should start another thread for the peformance problem. Best to stick to one thing at a time per thread.

 

Thanks for the feedback! I'll try swapping those relays and see what happens. If it doesn't cause any power related symptoms, I don't reckon that's my problem...

 

2 minuets back as a member and already finding good information. AWESOME!