Fuel pump relay, O2 sensor, MAF sensor

[andyrew]

OK,

So I am finishing up with the wiring on my custom build and there are 3 current stumbling blocks that are causing what I believe to be related issues.

1. The fuel pump relay is kicking out 3.5v to the green/yellow wire that goes to the fuel pump, I can trace this 3.5V back to the ECU that is kicking out 3.5v on the purple/black(iirc) wire that tells the fuel pump to fire. Not a big deal I am running a dedicated 10ga wire to both fuel pumps with a 30amp fuse from the keyed black/yellow terminal on the relay board.

2. My o2 sensor is giving me code P0130, This is after replacing the o2 with a new one.

3. My MAF sensor is not letting the car run when plugged in. I am getting a reading but its either not scaled right or the MAF sensor is not getting proper voltage. I am reading around 30 g/s at 2k. Its a brand new HFX Blow through MAF sensor so I know its not bad.


My thought. The 02 and MAF sensor seem to be powered by the same green/yellow wire, I am unsure if it is the same wire source that feeds the fuel pump. If that is the case then should I just put a keyed power source to the fuel pump green/yellow to get these in the correct power range?

I am going to check the power at the MAF and 02 sensor later tonight. but looking for other possible items to look for.

Car runs with the MAF unplugged.

[desireroom]

I remember that the MAF and the lambda probe are fed by the same wire fuel pump. It is more feeds several things and ends with the fuel pump. from then I send a photo of the scheme of that system.

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[andyrew]

Sounds like I need to force that green/yellow wire to have 12v and all my problems will solve themselves.

[chris164935]

Fuel pump relay outputs 12v to three different sources. One green wire goes to fuse 28 in the fuse panel then changes to a green/yellow wire that goes to the fuel pump (12v). Another green wire goes to fuse 32 and changes to a black/blue wire that powers the injectors (12v). The third output is a green/black wire that goes to fuse 34 and changes to a green/yellow wire that powers the N112 (Secondary Air Injection solenoid), N80 (Evap Canister Purge Regulator valve), N75, triggers the secondary air injection pump relay, powers the MAF, and the primary and secondary O2 sensor heaters (12v). Each one of these 3 outputs from the fuel pump relay are independent of each other, so one should not cause issues for the others.
I would check all the N valves I listed for the third output, it could be that you deleted one and the resistor or whatever might have shorted out. Or just an open connector caused a short somehow. Or could be faulty wiring to any of those things causing a short. Might be easiest to start at fuse 34 (make sure it is good first), then check resistances/continuity to each pin on each connector that the green/yellow wire goes to. For the N valves/solenoids the green/yellow wire goes to pin 1 on their connectors. For the secondary air pump relay, it goes to pin 4 (or terminal 86 if you using the diagram on the relay), pin 2 on the MAF, pin 3 for the primary O2, and pin 1 for the secondary O2.

Good luck!

[andyrew]

Fuel injectors are indeed getting power, the only things being used on the other are the o2 and MAF.

All the rest of the items simply are not plugged in.

I will start checking leads. Do you know which items I can leave open and which do I have to put resistors on?

Again, total custom build (see my signature..) so I have been trying to keep the oem harness as much as possible.

[andyrew]

Btw Chris your response was excellent, thank you!

[desireroom]

as you see in this picture there are several powered by the same fuel relay output components. Y68 and Y104 we ignore, maf and lambda probe are fed by the same (terminal 30, the relay output B7F fuel) would be voltage of battery (12v)


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[desireroom]

sorry for my English and my schedule, I'm from Spain and here already dawning hehe. Of battery voltage have'd see the car started 13.4V + or -

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[chris164935]

Fuel injectors are indeed getting power, the only things being used on the other are the o2 and MAF.

All the rest of the items simply are not plugged in.

I will start checking leads. Do you know which items I can leave open and which do I have to put resistors on?

Again, total custom build (see my signature..) so I have been trying to keep the oem harness as much as possible.

I believe all of them can be left unplugged. It just depends on your tune, etc. I know Motronic requires some N valves/solenoids to be connected or have a resistor put in place in order to adjust fuel trims automatically. If you're using Maestro though, that probably doesn't matter.

You can also pull your fuel pump relay and measure the voltage to terminal 30 (according to the wiring diagram on the relay) to make sure it is getting battery voltage. Also, you could pull the relay and jump terminal 30 to terminal 87a (according to the wiring diagram on the relay) and see if your O2 heater and MAF get 12v then. You won't have to turn anything on since terminal 30 always has a constant battery voltage.

[andyrew]

OK so I am going over everything and I notice that relay #30 by the ecu is warm. I know its feeding power constantly but I wouldnt anticipate a relay to be warm if it was functioning correctly.

Also the green wire in front of the fuel pump relay shows the same amps as what is being sent to the fuel pump wiring and MAF/o2. With or without the relay in place and at all times.


Side note, I jumped terminal 30 and 87a and got 12v to the MAF. BUT now the car wont start with the MAF plugged in. Going to check my MAF wiring but pretty sure its right.. Sigh.