A little confused on what needs power

**joegreen** · 06-13-2014

I printed out the wiring diagram for 1227747 ecu but i am confused on what pins get constant voltage and what gets switched. The injectors get switched. The fuel pump relay is switched. Does the ecu send out power to apply the fuel pump relay? I believe pins b1 and c16 have constant 12v. Basically i just need to know what pins get power and when. Sorry for my noobishness. On the plus side i have the fuseblock relays and wiring harness in the truck.

**joegreen** · 06-14-2014

So the esc and injectors and pin a6 i have tied together with switched 12v on crank and on. B1 and c16 always get power tied together. The coil gets 12vswitched with crank and on. The coil sends 12v to distributor through the 2 wire connector .

**joegreen** · 06-15-2014

So i think i have the power wires down. Next question is regarding the grounds. Some wires seem to get grounded to the ecu and some to the engine. But then some say chassis ground. Can i just ground all necessary things to ecm and the rest to the engine block. I read that its best to ground all things in one spot. Thanks

**EagleMark** · 06-15-2014

Nothing get's grounded to ECM. There are wires from ECM to ground and the ECM uses these to ground a circuit to turn it on, like injectors have power coming into them and the ECM uses a ground to complete the circuit.. or fire the injector if you will.

There should be two sets of ground wires, one is diret grounds for ECM to use and the other is grounds for sensors etc... system grounds and sensor grounds... it just takes a little time to go over wiring diagram and tackle them one wire at a time. Yes several wires can end up on same ground. Stock there are two ground circuits and they both end up on intake manifold bolts.

IIRC B1 and C16 get constnt power all the time. A1 does not! When key is turned on A1 puts out power to fuel pump relay to turn it on. Don't forget B2 that ties into the power going to pump, it comes back to ECM to let it know fuel pump is running.

A6 and the coil need to get power when key is on, all the way to crank and back to key on uninterrupted!

**joegreen** · 06-15-2014

a12 goes to engine ground and can be tied to d1.
a11 and 12 are solder connected in ecu so use them both as grounds.
a11 says map sensor ground. so does the map ground go to engine or a11?
d2 sensor ground goes to engine block
I think thats it d14 and d16 go to ground out the injectors to pulse them.
school starts for me in one week and i am stressing a little with this tbi thing. I really want/need this done before then. thanks for your help eagle mark on this post and others.

**EagleMark** · 06-16-2014

Originally Posted by joegreen

a12 goes to engine ground and can be tied to d1. Correct.
a11 and 12 are solder connected in ecu so use them both as grounds. Well, I've always kept them separate. One is a chassis ground and one is a sensor ground, I don't like to mix the 2. Sometimes if you look at 2 differant diagrams it will be more clear!
a11 says map sensor ground. so does the map ground go to engine or a11? Look at diagram! It goes to MAP sensor, it also ties into ground for TPS and then goes back to A11
d2 sensor ground goes to engine block D2 just goes to MAP sensor.
I think thats it d14 and d16 go to ground out the injectors to pulse them. No, they just go to ECM, the ECM has it's own grounds and uses them when it needs too like to pulse injectors.
school starts for me in one week and i am stressing a little with this tbi thing. I really want/need this done before then. thanks for your help eagle mark on this post and others.

HTH!