Car runs in safe mode: cel, keyl, seatbeltl all stay lit. Gutless acceleration,
Temperature and rpm gauges inoperative. Can can eventually get up to about 60 mph, but, you can't punch it, it boggs down. Dealer and other shops say their scanners can't read the ecm for code indications. They suspect the network bus (?) is the problem. Have no idea what this network bus is, nor how it got broke. Temp and rpm gauges were working before dealer looked at the car, and connected their scanner to the car (maybe just coincidental that they stopped functioning?) I'm not trying to blame dealer.

2003 honda civic ex, auto trans, vtec 1.7 engine

Try installing a known good ECM.

The Honda dealer did in fact install a new ecm, but, it still did not solve the problem.

Performance issues on your generation of Honda usually involve the ECM or Crankshaft Position Sensor.

I assumed the network bus they were referring to was the bus inside the ECM. Apparently, that's not the issue. Without more information, I'm not going to be of much help.

We had one of the Japanese engines installed a couple of months ago. It ran good for about a month, then these issues surfaced. In the process of diagnoses, the dealer installed a new ecm, they thought they had it fixed, but, car still had symptoms mentioned. So I had them re-install old ecm, same symptoms persist. We've spent over $4000 this past couple of months on this car and now feel we have to eat it and take it to the wreckers! I'm not confident I can find the problem, especially after having honda dealer, and two other shops look at this car. All the last shop says... they thinks it's the "network bus???"

Were both engines identical (i.e. same engine number)?