DTC codes 18 &35

[kenisret]

Has anyone experienced these codes and were able to correct them by eliminating alt. interference bby installing a filter wire harness on the optical sensor on the inj. pump? I have a feeling my pump may be going bad although it only has 56000 miles on it.I understand water in the fuel is the most common cause of optical sensor failure.I have never had a water in fuel light come on and I filled a glass jar with fuel from the the fuel filter drain line and it was free of water.I keep getting code 18 and once in a great while I can get it to reset but it keeps coming back and you can tell it is in limp mode.I want to eliminate all possile causes before I change the pump.Any ideas?

[gmctd]

Some '94 and '95 required the OS filter, so all got one - remove yours and see if the symptoms improve.

The connectors were crimp-only and would fail - if so, Bill Heath carries the replacement part.

35 is also caused by bubbles in fuel, failing lift pump, plugged filter, etc, anything that restricts fuel supply, even low fuel level in tank