I have a 1999 Dodge 2500 4x4 with 5spd. The engine runs great when it feels like it. Sometimes it will just crank over and won't start. Some times when driving the tach. will stop working and then it will throw a code. If I stop the engine with the tach not working it won't turn on the lift pump to feed the injector pump. If I turn the ignition on and off three times it will bring up a P1693 Critical injector pump failure. Once reset it starts right up. once in a while I will get the Companion ECM comm code. I think it's wiring harness or ECM problems. This has been going on for years.

Thinking about changing ECM

Any Ideas

Thanks,
Glenn