01 psd excursion not starting

[kirb]

I have an 01 psd excursion that died on the way home last night.. Cranks but won't start. It is getting the p0603 code Keep alive error. It has started 2 times today after long cool down periods. It will run for about 5 min. and then shut off. No funny sounds or anything, just shuts off. Then won't start again for several hours. I am getting fuel and have replaced the cps. Any ideas what it could be? Thanks...