This 1997 Chevrolet S10 Blazer cam in with the service engine soon light on and a complaint of low power. Checked data with Tech 2 scan tool and found codes P0102 MAF sensor circuit low frequency and P0340 cam position sensor circuit. I checked CMP retard and found it fixed at -60 degrees. I talked with the customer and found that the distributor had been out for some other repairs. Sounded like the distributor (cam sensor is built into it) needed to be set. Removed the distributor, reindexed the rotor and installed. The engine ran but I could tell the timing was way off and strangely the cam retard was still at -60 degrees. I put the distributor back to where it was originally and started doing some research.
I found a case where the ENG-1 fuse was blown causing the same thing.
I checked the fuse.
Sure enough it was blown and replacing it corrected both codes.
CMP retard also reset to -7 degrees. A little off but within allowable specifications. Perfect would be 0.
Now what caused the fuse to blow. Kind of strange that there is a new fuse just below the
ENG- 1. What is that for?
The radio of course. Some one in the course of trying to keep a piece of junk radio installation going pulled the ENG-1 fuse, put it in place of a blown radio fuse and put the blown fuse back in the ENG-1 fuse holder . Blew again and decided to buy new fuses but never bothered replacing the ENG-1 fuse. Recommended having the radio properly wired but the customer declined at this time. No surprise!!!