GM MAF install with ECU+: ECU stays in open loop

[donmagicjuan]

I know my chances are pretty slim of finding someone out there using ECU+ to translate the GM MAF signal, but some of you ECU savvy guys might be able to help me just the same.

I just installed a 3" MAF in a blow-through configuration and made the necessary wiring alterations to the ECU+ head unit. To give you a quick rundown, I had to route the MAF output signal into the head unit in place of the stock one, and simulate air temperature and pressure signals to the ECU using 2 of the analog outputs from ECU+. I have the air temp voltage set to 2.37 volts, which indicates 78-80* on the logger, so I'm pretty sure that's ok. The pressure signal is set to 3.90 volts, which I'm not sure what translates to, but the car runs, so I'm alright with it for now.

My problem is that the ECU will not come out of open loop (accel/decel). I've checked voltage to the MAF at 12V, so nothing seems wrong there. When I log translated MAS frequency, it doesn't appear to change when I rev the engine in neutral. Yet, the engine runs extremely rich, and gets richer as RPMs increase (could be a side effect of the simulated pressure signal).

The MAF is oriented correctly for the direction of airflow, and I've double-checked the wiring connections.

Anyone have any suggestions for resolving this?

 

[donmagicjuan]

As an update, I've narrowed down the problem to an absentee MAF signal. I either have a defective MAF (brand new --> highly unlikely) or a fried ECU+. I've checked continuity from the MAF to the ECU+ to rule out interconnecting wiring. My only guess is that the heat from soldering the wire to the ECU+ lead damaged the circuitry.

As soon as I isolate the fault to one of these components, I'll post another update and some possible lessons learned. To anyone thinking of running a similar setup, please do not be discouraged by this hangup. I know that many people are currently using ECU+ as a MAF translator with great success. Even more are doing so in the Evo community. My hope is that I can post some helpful suggestions to ensure this doesn't happen to anyone else.

 

[sbiggi]

I thought the maf uses a 5v signal?

 

[donmagicjuan]

You're right if you're talking about the stock MAS, but the GM MAF requires 12V.

 

[FORMONTOYA]

I don't use a MAF, and the power feeding the MAF might very well be 12v (I'm not doubting you), but what about the signal out?

edit...sorry, I re-read a little better and see you're looking at the output.

 

[donmagicjuan]

Don't sweat it, Jim. I really appreciate you taking a look and trying to offer something. It's looking more like MAF sensor and not the ECU+. I might try a different source, as I currently have it tapped off the fuel pump test connector. If anyone has any knowledge as to why this wouldn't supply a constant 12V, please let me know. All I know is that I tapped my fuel pump relay from this source when I did the rewire, and it works fine for that. My voltmeter is garbage, but it reads the same value as battery voltage when I check the supply line with the ignition on.

 

[FORMONTOYA]

Of course I'm just throwing thoughts out there....

You mentioned that the voltage is the same with the ignition on, is just the key on, or is the car running with an actual load on the system?

If not the same....maybe you could "scrounge" a relay, fuse holder and some wire and tap directly off the battery for the power feed (fused of course) to the MAF using the ignition as the "switch" for the relay to see how that effects things. Maybe for some reason with the combined loads it's pulling the voltage down and you're just not noticing it at the fuel pump because the fuel demand is not great enough out of boost.

Just a thought.

 

[donmagicjuan]

I've checked the supply voltage against that of the battery with the ignition in ON, both with the car running (like crap) and with the car off. Each time the voltages are the same. Sorry for the confusion, but I have the source tapped to the line feeding the fuel pump relay, not the actual fuel pump. My logic was that a relay in parallel with the MAF shouldn't have that much of a detrimental effect on the voltage. I will try a different source, though, probably just as you've described to isolate either that or the MAF. Thank you for the suggestion.

 

[donmagicjuan]

Before going through the hassle of rewiring the MAF, I did a check of the resistances across the pins of the sensor. I found that there was infinite resistance between the 12V power supply pin (pink wire) and either of the two other pins. This seems odd to me, although I don't have access to a schematic of the sensor to deem it faulty. Does anyone running this sensor happen to know (or feel like checking) if this is normal?