4 wire MAF voltage questions

Post by **subzerocarfanatic** » 26 Oct 2019, 17:37

I should be getting 12 volts when the key is on at one of the wires. i am not sure which one, the picture i seen with instructions i don't think is for my 2000 volvo c70 HT 2.3, and the wires that were numbered are different order than mine are. Mine has a green wire red stripe on one end,brown wire with white stripe next to it, the one beside it is purple with white stripe and the 4th one is solid green,it's a 4 wire MAF harness has 5 plugs but one has silicone plug and no wire there. The brown wire with stripe is the only one that shows any kind of voltage but it only shows 8 volts or barely over if i have volt meter on correct setting.Any help is much appreciated.

Post by **abscate** » 26 Oct 2019, 19:53

Pin2 on the MAF IS Green orange and needs to be close to battery voltage om ME7

If it isn’t, both the MAF and fuel injectors won’t work.

Trace the voltage back to the fuses, relays and find where you are losing voltage

Post by **subzerocarfanatic** » 27 Oct 2019, 12:13

what is ME7? Thanks. So is it possible i'm losing voltage between the MAF connector harness and ECU, assuming it goes there from the MAF plug. I traced battery positive to fuse box, the 4 red wires the bolt to nut inside fuse box, it was corroded bad, i replaced it with a 4 gauge wire and soldered the old connection on the end and new connection on battery end as well.

Post by **subzerocarfanatic** » 27 Oct 2019, 12:24

Where does the MAF wiring harness lead to so i can trace where im losing power if i am?

Post by **Clemens** » 27 Oct 2019, 14:30

ME7 is the 99 up motor management system as opposed to Motronic 4.3 and 4.4 in previous years.

Post by **abscate** » 27 Oct 2019, 15:43

ME7 is the name of the ECU software

All of th MAF wires run to the ECU except the 12V supply which goes to a common Bus with the fuel injectors

Post by **RickHaleParker** » 27 Oct 2019, 16:07

7/17 is the MAF.

Pin 1: Not used
Pin 2: GN-OR (Green/Orange) Power
Pin 3: BN-W (Brown/White) Data
Pin 4: VO-W (Violet/White) Ground
Pin 5: GN (Green) Data

Pin #2 GN-OR is a common power node (23/11) shared with the fuel injectors. Should be 12-14V. Check the voltage at solid Green wire of the fuel injectors. Is the Voltage low there also? Defective injectors could pull the voltage down, disconnect one at a time, watch voltage. Defective MAF could pull down voltage, disconnect MAF, watch voltage.

Pin# 4 VO-W is a common ground, provided by the ECM.

Pin# 3 & 5 is the sensor data.

Post by **subzerocarfanatic** » 27 Oct 2019, 20:51

So if everything runs back to the ECU how and where do i check for power loss, do i trace the MAF plug wires to the ECU and trace the green one that has power to the fuel injector harness and do i check the fuel injector plugs at each injector or do i Ohm check each injector instead of testing for volts? I apologize for the noob questions but I have a lot to learn about Volvo's and this is the best place to do it. I appreciate the input and help more than i can express!

Post by **subzerocarfanatic** » 27 Oct 2019, 23:30

abscate wrote: ↑27 Oct 2019, 15:43 ME7 is the name of the ECU software

All of the MAF wires run to the ECU except the 12V supply which goes to a common Bus with the fuel injectors

If i done it correctly, the injector i tested had 12.5 Ohms, I just used red probe and black probe from multimeter to the 2 pins on injector. the voltage going to injector plug was 3.5 volts with key on. I set the meter to volts DC,is that correct, My meter has DC mA and DC V 10 MegOhm Input, the 10 MegOhm input DCV is the one i use, I had the voltmeter black probe on battery negative side and the red probe on one of the 2 pins in the injector plug harness. 1 more question, i removed the blue screw on cap off the schrader valve on end of fuel rail to relieve fuel line pressure, i pushed it in 4 or 5 times and there was still fuel coming out, and it was not dripping out, it still seem to have pressure behind it, i removed the 15 amp fuse for fuel pump, am i missing something or do something wrong, i thought the fuel pressure would drain off when relieving the pressure off the end of fuel rail like i did. Also, do all the fuses in fuse box supposed to have 12 volts to them with battery connected and key on or off because some of them did not have 12 volts. thanks again for the help.

Post by **subzerocarfanatic** » 28 Oct 2019, 11:35

what should the injectors have for Ohms, i only checked one, it was 12.5 ohm's , i will check the rest now and report back my findings. I will test the green wire to each injector plug to see if i'm getting 12 volts with key on and report findings as well. thanks!