No constant 12v to ecu

[94_TSi]

Alright heres the deal car is a 92 tsi awd 5spd. Im finishing up the build on it and this has me at a big stand still. Here are some things that may be of interest.

Battery relocated to hatch
Underhood fusebox moved to stock smic location
Zero blown fuses
Engine is out

While waiting on some parts I decided to get dsmlink setup and ready to go. Tried to connect and no go, double checked everything with it and its fine. Checked for 12v to ecu and have it from the mpi relay but no constant. There is also no check engine light when I turn the key on. Took 12v directlly from battery and got some more dash lights, underdash lights and some other interior stuff did not howev er see the check engine light. At this point I figure I have a short so I took the meter to continuity and put it to pin 102 from ecu to ground. Got the buzzerso I start tracing the 12v(pin #102) constant wire back.

There is a harness connector right under the center of the dash, close to the shifter cables. I detached the connector and checked from the ecu pin to ground and got nothing so I concluded it must be on past that section. If i go from the other side of the connector to ground I get the buzz again.

I removed the dash and the under dash wiring harness and cant find any issues with it up to where it goes above the fusebox of the drivers kick panel area.

Can someone point me in another direction please?

 

[yokotabrat]

Were you doing your continuity testing to ground with the ecu plugged in? Were you doing the continuity test with the key turned to the ON position? Where are you measuring 12V from the mpi relay? What pins on the ecu or mpi relay?

Pin 102 should go to the MPI relay, same as pin 107. Pin 103 is the constant 12V supply. Measure the voltage on pin 103. Also, make sure your MPI fusible link is okay. Measure the voltage at pin 10 of the MPI relay. That should be 12V all the time assuming the MPI fusible link is good. Pin 63 on the ecu should go to approx 0V when the key is in the ON position. Check that one also.

Let us know what you find out.

 

[94_TSi]

Thanks for the reply man.

Ya your right pin 103 is constant 12v and that was the one i meant not 102. Heres the deal now, I have all the correct voltages to and from the mpi and ecu.

I have 12v at all times to pin #10 at the mpi relay. Pinins 4 and 5 i have 12v with the switch in the on position. At pin 8 I have 12v until switch is turned on and it drops to 0 like it should. Constant power to the ecu is good as well as switched power now.

Now I still have no check engine light with the key on and therefore cannot connect to dsmlink. I have tried three known good ecu's. No popped fuses I dont know what the hell is going on here. Any advice at all will help

 

[94_TSi]

Nobody?

 

[yokotabrat]

There's not much else. You have switched power and constant power. You could check to make sure your grounds are good (pins 101 & 106). Check pin 1 on the ecu to see if you get the ecu's "heartbeat" signal. It should vary from 12V to 0 at a constant rate. If so, your ecu is powered up and there's just something wrong with your CE light bulb.

 

[94_TSi]

Well checked the bulb with the meter then switched it with two other ones to make sure, it is good. Also I put my ecu in a buddys car that the trans is out of and it gives the cel like it should.

 

[yokotabrat]

Check for that heartbeat signal, then. That will tell us if the ecu is booting up. What does the stock boost gauge do when you turn the key to ON? Can you connect to dsmlink when the ecu is in your friends car?

 

[94_TSi]

Check for that heartbeat signal, then. That will tell us if the ecu is booting up. What does the stock boost gauge do when you turn the key to ON? Can you connect to dsmlink when the ecu is in your friends car?

I will check the heartbeat signal. The boost gauge goes to zero then does not go back down. I didn't even try to connect to link when it was in his car, The cel came on so I was happy. Thanks agian yokotabrat.