I have a 1998 Cummins 24v with 190,000 miles. About 3 miles into a trip, I felt the truck loose a bit of power. About 10 miles into the trip, I started getting intermittent loss of power, which occurred approximately once every two minutes. The check engine light turned on, as well. I exited the freeway and stopped at an auto parts store. The codes were all ECM related. I drove home on back roads.

Codes

• P1698 - ECM Fault-no CCD message from TCM (probable cause Open CCD bus line or failed TCM)
• P1696 - ECM EEPROM fault write denied, attempt to write to EEPROM denied (probable cause ECM defective, service reminder module failed internally, information between modules needs updating
• P1693 - Tachometer Circuit Fault, ECM has detected an open or short circuit condition in the tacho

meter circuit (probable cause Open or short circuit condition, defective tachometer)

A bit of history
A few years back, I had someone syphon my fuel. They left the cap off. I wasn’t driving it and I didn’t notice it for two months. I had air in fuel system, which I had to bleed from hard lines. No issues since. I don’t run any type of additives to my fuel but was recommended CRC Fuel Injector Cleaner first just to make sure that isn’t the issue. Codes dont suggest this. My number greatest concern has always been the lift pump failing, resulting in the injector pump failing.

When I had air in the fuel line, the truck would loose power. My current issue is similar; however, I notice the tach is sporadic and it almost feels like all the cylinders are not firing properly. The codes don’t seem related to the fuel system considerations.

Any suggestions to the steps I should take to diagnose? I suspect maybe the harness.