niscur29
09-26-2011, 07:05 PM
Ok so heres the deal with my ECU power issue…I pulled apart the relay box and the plugs at the body/engine connectors nothing was crossed/frayed and it looked almost new for a 20yr old car. With the key off and the ecu unplugged the EGI relay plug outputs nothing on the b/w wire. With the key on and the body/engine plug disconnected and ECU plugged in the b/w relay wire is dead. If I plug it all in the my ECU has 11.3 to 12 volts flowing through the ECU into the black/white wires and causes the b/w wire on the relay plug to get the same voltage (with no relay in there). I even plugged in a second stock ECU and the same thing happens. The ecus are getting the right voltage on the switched ignition pin 36 however I am not getting a ground signal on pin 4 for the EGI relay to be tripped.
Now the way I understand ECU power is as follows:
1. ECU always has 12V as a backup on the red wire
2. Turn the key to ON and switched 12V comes in via pin 36
3. Pin 4 should ground out triggering the EGI relay and a ground signal on the relay pin with the relay out
4. Once the relay senses the ground trigger, the relay closes throwing 12V from the other side to the b/w wire all the way to pins 38 and 47
So Right now I have #1 and #2 however both ECU’s are sending 12v out on the b/w instead of receiving it from the relay and the ECU is not on. Continuity checks out all the way from the ECU to the relay . I can’t believe I have two bad ECU’s and I suspect the engine harness but even then continuity exists and why would the ECU’s be outputting voltage. Now both ECU’s where plugged into the car after it stopped running at one point (In trying to diagnose WTH is going on I forgot the stock one wont work with ls coils) so I could have fried both of them. This is a friggin brand new OE (not OEM) harness which means it could be shit or be kinked/frayed somewhere already but should be fixable. Thoughts? This car was driveable prior to it sitting while it was painted.
Now the way I understand ECU power is as follows:
1. ECU always has 12V as a backup on the red wire
2. Turn the key to ON and switched 12V comes in via pin 36
3. Pin 4 should ground out triggering the EGI relay and a ground signal on the relay pin with the relay out
4. Once the relay senses the ground trigger, the relay closes throwing 12V from the other side to the b/w wire all the way to pins 38 and 47
So Right now I have #1 and #2 however both ECU’s are sending 12v out on the b/w instead of receiving it from the relay and the ECU is not on. Continuity checks out all the way from the ECU to the relay . I can’t believe I have two bad ECU’s and I suspect the engine harness but even then continuity exists and why would the ECU’s be outputting voltage. Now both ECU’s where plugged into the car after it stopped running at one point (In trying to diagnose WTH is going on I forgot the stock one wont work with ls coils) so I could have fried both of them. This is a friggin brand new OE (not OEM) harness which means it could be shit or be kinked/frayed somewhere already but should be fixable. Thoughts? This car was driveable prior to it sitting while it was painted.