2zr MAF amperage draw, help needed

[atomic_hoji]

Awesome find Trevor - I mean awesome as in well done, because the problem is really a pain in the ass and not awesome..

I had a suspicion the same suspicions you describe re: a parasitic draw in the Fall after letting the car sit for a few days, then with the wicked cold lately I ran into the same problems: 2 days and she needs a boost. I actually keep a charged truck battery in my back-seat so I can get home from work; just in case. Just haven't had time to look into it with exam this past Friday, then low an behold you brought it up.

I just did a quick check, and sure enough, with the MAF plugged in I get about 250-300mA, bouncing around some, then after 60s it drops to about 185mA. If I disconnect the MAF and do the same test, it's immediately lower, about 150-180mA and after 60s drops to about 100mA. Definitely seems to be contributing to the problem for me, and would explain your 90mA draw pretty well.

Trick now is to find the solution - without unplugging the MAF every evening.. lol

-- Adam

[tmontague]

Originally Posted by atomic_hoji

Awesome find Trevor - I mean awesome as in well done, because the problem is really a pain in the ass and not awesome..

I had a suspicion the same suspicions you describe re: a parasitic draw in the Fall after letting the car sit for a few days, then with the wicked cold lately I ran into the same problems: 2 days and she needs a boost. I actually keep a charged truck battery in my back-seat so I can get home from work; just in case. Just haven't had time to look into it with exam this past Friday, then low an behold you brought it up.

I just did a quick check, and sure enough, with the MAF plugged in I get about 250-300mA, bouncing around some, then after 60s it drops to about 185mA. If I disconnect the MAF and do the same test, it's immediately lower, about 150-180mA and after 60s drops to about 100mA. Definitely seems to be contributing to the problem for me, and would explain your 90mA draw pretty well.

Trick now is to find the solution - without unplugging the MAF every evening.. lol

-- Adam

thanks a ton Adam for replying to this thread and checking your MAF draw, you saved me a $100 purchase off of RockAuto for a Denso MAF. Really interesting to hear you have essentially the same issue - I'm assuming you wired your MAF power to the LH light bulb fuse like we all did?

I would love to hear about others with their 2zr swaps and what their amp draw is with their MAF disconnected and connected. I have a feeling that the LH light bulb is not ignition switched like the power source the MAF needs. The headlights don't need the ignition on to work as long as you switch them on. I never actually tested that fuse to see if it was ignition switched as I just tapped into it based off of previous swap instructions.

I tested my 1zz MAF on my Vibe and sure enough, there is no effect on the amp draw with the MAF disconnected and it would make sense that the MAF needs no power while the car is off.

I had a few electrical issues which is why it has taken me a while to get down to the bottom of this and likely why this has never caused me a problem when I first did my swap. I had a low charging alternator (11-12.4V) which CT originally said was a bad battery. I only started to test the alternator and monitor my voltage gauge when I had the same issue with the new battery. New alternator solved that issue.

I also found out last night that I had an issue with my keyless entry where it would randomly trigger the internal relay in its computer and sometimes even turn the dome light on in the middle of driving. This started late last year. I didn't know until last night during testing that is was actually keeping the ECU-B circuit from going to sleep therefore drawing an extra 110mA consistently overnight.

From my testing last night I found the following for a 2zr swapped yaris:

-Normal parasitic draw (No MAF, and ECU asleep): 30-40mA
-ECU asleep with MAF wired up: 120mA
-MAF wired up and bad keyless entry causing ECU to be awake: 260mA-320mA

Base amperage draw from each device:

-ECU asleep: 10-20mA
-ECU awake: 120-130mA
-MAF: 80-90mA
-keyless entry 20mA

With the above info there is about 20mA of "unaccounted for" amp draw, this makes sense and would cover the clock as well as the light for the immobilizer. 30-40mA is a value that is very acceptable and would not cause my battery to die for a few weeks in the dead of winter and likely 2 months in the summer.

The issue I'm having is the extra 90mA from the MAF, plus the 120mA from the ECU that was caused by the faulty keyless entry module. This extra 210mA of draw is enough to cause a no start in 2 days and even over night in -25C weather.

I replaced the keyless entry with a new module I had lying around. If this one doesn't start randomly clicking on me then it should have fixed the issue. I tested it and it worked properly and allowed the ecu to go to sleep.

I am now down to about 130-140mA total draw with the MAF connected. This is much better but it is still too high and something that should be addressed with the cold we get here.

My next step is to test the fuse that the MAF wire is tapped into with the fuse tap. I am going to try and use another proper ignition switched source and see if that addresses the problem. This would also be why the warm weather 2zr swap guys have never had an issue. A 130-140mA parasitic draw is not enough to kill a battery in warm weather starting unless it sits for well over a week