Jesus Freak

So my thread isn't getting any response, so I'll post this as an individual question.dum

I have a GMPP harness kit with my ls376/480 + tci 6x trans.dum
ECU part# 19201790

I had the car running great. Started every time, drove it twice. I let it sit for a day, came back and now it cranks but won't start. I have no power to the fuel pump and my PLX OBD2 won't connect. I've verified all fuses are good, I have 12v constant and 12v switched power to the fuse block. And it sounds like the relay is clicking, I tried switching two relays just in case and it didn't work.dum

Any suggestions?

psiconversion

iTrader: (5)

Remember that the PCM is providing constant power. If you jumper power to the relay will it work? If so, then the PCM is not providing the power. If that is the case, either the PCM is not getting switched power or ground.

Jon
PSI

Jesus Freak

So I was getting intermitten continuity with the ground leads to the relays. I took the ECU out of my box (plastic) and set it on the shock tower, I noticed the relays turned on. So I made a jumper wire to go from the body to the body of the ECU and all is good.

Now my question is, why did it work for 3 days straight? And shouldn't it be grounded through the harness? The instructions don't say to ground the body of the ECU.

gMAG

iTrader: (1)

The manufacturer may have assumed that by bolting/fastening the ECU to the frame, that the ground would be taken care of. That would be a pretty big ASSumption (by the manufacturer)!

Redbull87

iTrader: (3)

I rewired my harness to avoid issues like this for simple diagnosis by connecting all the grounds together and running a single 8ga ground from the battery to the ecm,same for the main power to the ecm,then a small 10ga ground from the ecm chassis to a ground bolt just incase.All my switched 12v wires are together and supplied by 2 40amp relays drawing power directly off the battery aswell.

1975delta88

I have the same problem with my E-rod LS3. It cranks, but it won't start. Although my fuel pump does turn on. I had my ECU mounted on my fender well with MSD anti-vibration rubber mounts. I have the harness grounded to the engine x3, two more grounds from the engine to the firewall. I have the switched power connected to the ignition switch and constant connected to the battery. My scanner won't connect to the ECU at the OBD2 port. I ended up having to get the ecu exchanged for another one before my warranty ran out. I 'll give that a try once I get the replacement.

Jesus Freak

We're you getting an injector signal? I missed the crank sensor plug the first time I tried to start it up.