ECU light not flashing. Bad ECU?

[Georgesteve]

My 1990 300zx NA 5 Speed turned off while i go downhill three times. I try to run a Diagnosis on the ecu but the little light does not flash. I followed the instructions and even looked up videos on how to do it. Could i have a bad ECU. The car runs fine in the city even though the check engine light is on. I already paid 300 dollars in towing so i rather fix it asap.

Thanks,
George

This is my first post.

[NolimitZ32]

If it only happens when the car goes down hill the cause is very likely a loose or bad ECU ground. Time to break out the wiring diagram and check every single one.

[t.mcginley.jr]

Wiring diagrams: http://www.ttxtz.com/tech/lee/

[Georgesteve]

But how about my ECU, the light is solid red. Shouldn't it at least shoot out the code 55 saying that everything is OK in mode 2.

[Georgesteve]

Ok guys so i checked to see if there was any loose ground and I found one. The ground bolt next to the battery was hand loose. I tightened it and went up and down some hills by my house, the car didnt turn off. Could this of been the problem?? Thanks.

[NolimitZ32]

Sounds like that could be the first part. Continuous on/off and bad ground connection could have cause other problems or damaged some of the delicate ECU internals, drive it around for a bit and pray that everything is fine, it wont take to long for other problems to show up if they are there. As for the ECU LED staying on; generally that means the ECU is bad, best way to check is to get another known good ECU and see how it reacts in your car and vice versa for your ECU. Sometimes a car will run with a bad ECU but then all of a sudden not. Deeply and internally testing an ECU's components is not a DIY procedure.