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Old 11-09-2021, 09:29 PM   #1
TheHolyGhost
 
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Default Troubles With MAF after installing SAFCII

Hello everyone, this is my first post on here so please be gentle.

I will preface this by saying I have been crawling forums for the last week to find an answer to my issue to no avail, and I have tried the search function on here to no avail as well.

I have a 1995 Hardbody, 2.4L 5 speed manual, 2WD
My mod list is as follows:

240sx intake manifold and fuel rail, stock FPR
DW 550cc injectors
Innovate LC-2 wideband (sends narrow band to ECU in place of stock narrow band O2)
Walbro 255
Z32 MAF
Unkown Turbo kit on it, with FM intercooler
SAFCII
I have removed/deleted all of my emissions and EGR equipment.
I have no IACV as my 240sx intake did not come with one, I know its not recommended but it is not my issue at the moment, I'm in the process of getting one ATM


The truck ran like a top prior to putting my turbo kit on it and installing my SAFCII.
I am having my ECU throw code 12 and 41. The engine is cutting out at 2500 rpms.

12= MAF sensor

41= AIT sensor

All wiring has been checked, double checked, and triple checked. I am 90 percent certain that my MAF is grounded properly, I am getting signal from my MAF to my SAFCII @ 1-1.1 V at idle. All engine grounds I could identify and find were verified and are good. I have verified that the MAF is not the issue, I swapped out my old one with my friend I got it from with one I watched him pull out of a running 300zx. I am getting 12V at the MAF for power, ground is reading continuity on both C and D, and my signal wire is sending the proper signal to my SAFCII. Coming out of my SAFC, When connected to my ECU on pin17 it is reading -7 to -9 volts.

For curiosity sake, I disconnected my signal out from my SAFC and read the voltage and it was around 1.1V. When I checked pin 17 on the ECU (where the signal wire from the MAF goes into it) to see if any signal was coming from from it, it was reading -7 to -9 volts, and dropped upon acceleration to around -4.9 to -6 depending on where the engine was at rpm wise (limited to 2500 rpm)

My SAFC setting are as follows

Sensor type: Hotwire, 2 in 5 out: 1in 1out
Vehicle type: 4 CYL, arrow ascending
LO throttle is -%50 across all points
Hi throttle is -%50 across all points until issue is figured out
TH-point: Lo 15% Hi 50%
Dec. Air: Thr: 1.0%, Ne1 4.8 Ne2 5.8

I am at a loss as to what the issue is. I have swapped in 3 difference ecu's, tried every combination of sensor type configurations, and am beyond frustrated that I cannot figure out my issue and am on the verge of sending my truck to a scrap yard. Is that voltage coming out of pin 17 normal? I have read the FSM for my truck and it shows pin 16 as your MAF wire on the pinout, But it is a black wire that reads 1V to 3V coming back from the MAF, which from what I read and understand is from the ground for the MAF. From what I have read the ECU should have no wires showing negative volts coming out of it, especially not the MAF pin. Any ideas? Any help or direction at all is greatly appreciated!

Last edited by TheHolyGhost; 11-09-2021 at 09:39 PM.
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Old 11-10-2021, 01:19 PM   #2
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2500 RPM cut out indicates "Limp home mode"
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Old 11-10-2021, 06:06 PM   #3
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Hi Resurector, I appreciate the reply, but I should have stated in my original post that I am aware it is in limp home mode as it is throwing code 12 for the maf, which will cause it to go into limp mode and restrict rpm to 2500.
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Old 11-11-2021, 12:23 AM   #4
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What ecu are you running? What maf are you running? When I swapped the 240 maf in on the truck ecu there was 2 wires that needed to be swapped. Just an idea.
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Old 11-11-2021, 11:54 AM   #5
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What is SAFCII? Is that a different ECU?
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Old 11-12-2021, 01:55 PM   #6
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Quote:
Originally Posted by jp2code View Post
What is SAFCII? Is that a different ECU?
Sounds like A "microsquirt" type of system. (piggy back)
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Old 11-13-2021, 08:09 PM   #7
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The SAFCII is a Apexi Super Airflow Converter 2, I take your MAF input signal and modifies it to trick the ECU into changing the injectors duration, in my case with 550CC injectors it take the signal and reduces so that the ECU only sends half the required amount of pulse/ signal to the injectors so it does not run crazy rich. PoBoi you are correct, it is a piggy back system.

91Nissan94, I am currently running the stock truck ECU with a Z32 MAF out of a 300ZX. under normal circumstances the truck would reject the Z32 MAF but with the SAFCII it can change the output signal to what the truck is looking for. I have tried it with the 240sx ECU as well.

I have two truck ECU's
The one that came in the truck is : HR PHR MECM-E111, A1, 5719
The second one I picked up is : J8 PJB MECM-E120, B1, 4914

The 240sx ECU that I have tried is number 10, A11-B15-G02 which came out of a manual 1989 240sx, Federal emissions with the 8.6:1 KA24E, Nissan part number 23710-40F04

Unfortunately my ECU identification chart does not show anything for the two truck ECU's I have, the latest model truck ECU listed is 1993.

I am curious my friend, which two wires needed to be switched? Maybe I missed something in my scouring of diagrams and forums!
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Old 11-13-2021, 08:21 PM   #8
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If you look at the 240 intake swap how to you will see. It has been a long time since I did mine. I just remember having to swap them.
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Old 11-13-2021, 09:01 PM   #9
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I know on my swap the MAF wires needed to be reversed. Instead of color matching w/w and b/b I did w/b and b/w. My MAF codes were corrected and OBD II worked as designed after that.
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Old 11-16-2021, 09:06 PM   #10
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91Nissan94 I have looked through all of the swaps I can find, I could not see anything about swapping two wire.

dvdswan, I have tried switching the wires, as well as running wires separate from the wire harness directly to the ECU. It is not a wiring problem between the MAF and the ECU.
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