Have been living with the DTC 35/36 trouble code for thousands of miles now. Only driveability issue is with the cruise control which shuts off when the SES light blinks on. I've tried everything else, like replacing the lift pump, relocating the PMD under the front bumper, swapping out the PMD, rechecking all of the grounds, new fuel filter, gallons of diesel-clean, etc. I'm thinking it must be optical sensor.

Except for that, the truck runs better than new. After installing Heath's recommended chip upgrage 5 years ago, it starts quickly with little or no smoke and runs in all kinds of weather better than ever before.

What would you do? Should I leave well-enough alone or do an expensive pump replacement? Is there any other reason to change out the pump other than to have cruise control?