2005 Mustang 5V MAF sensor problem.

[Laga77]

I have a 2005 Mustang GT. It is modified with Edelbrock SC, cams, headers, E85. I did all the mods. It was running great. I then damaged the automatic transmission. It sat for a couple of months until I could make arrangements for a repair. I had to hire a local mechanic to remove and then reinstall transmission. Afterwards it ran terrible. The mechanic had switched upstream O2 sensors. Bank 1 to 2, 2 to 1.
I fixed that, but it still ran bad. When I did a datalog, I found MAF was not working. I tested wiring, and it was fine. There was no 5V power going to MAF sensor. There is 5V going to fuel pressure sensor and throttle body position sensor. Since they are all on one source from PCM. I thought the PCM was bad. After installing a PCM replacement, same problem. No power coming out of pin on PCM for MAF. Everything else works perfectly. My tuner (Lito), who has been tuning Mustangs for over 20 years has never heard of this problem. I’m thinking the wiring to the O2 sensors are shorted somewhere. They are 5V also. I need to take it somewhere since my health prevents me from crawling under cars now. Any other ideas?

 

[iCurious]

I have a 2005 Mustang GT. It is modified with Edelbrock SC, cams, headers, E85. I did all the mods. It was running great. I then damaged the automatic transmission. It sat for a couple of months until I could make arrangements for a repair. I had to hire a local mechanic to remove and then reinstall transmission. Afterwards it ran terrible. The mechanic had switched upstream O2 sensors. Bank 1 to 2, 2 to 1.
I fixed that, but it still ran bad. When I did a datalog, I found MAF was not working. I tested wiring, and it was fine. There was no 5V power going to MAF sensor. There is 5V going to fuel pressure sensor and throttle body position sensor. Since they are all on one source from PCM. I thought the PCM was bad. After installing a PCM replacement, same problem. No power coming out of pin on PCM for MAF. Everything else works perfectly. My tuner (Lito), who has been tuning Mustangs for over 20 years has never heard of this problem. I’m thinking the wiring to the O2 sensors are shorted somewhere. They are 5V also. I need to take it somewhere since my health prevents me from crawling under cars now. Any other ideas?

You will definitely need a wiring diagram for this. Check what else is tied into the 5V REF with the MAF sensor and disconnect all of them until the 5V is back.

You sure the wire is not broken? Grounds are good?

 

[Laga77]

You will definitely need a wiring diagram for this. Check what else is tied into the 5V REF with the MAF sensor and disconnect all of them until the 5V is back.

You sure the wire is not broken? Grounds are good?

Disconnected wire at PCM connection to check continuity. It’s good all the way to MAF pin. Re-did PCM and MAF ground about 2 years ago. Checked them now and still good.
I do have wiring diagrams. I’ve talked to two local shops and they don’t want to touch it. May have to reluctantly take it to dealer. Thanks.

 

[iCurious]

Disconnected wire at PCM connection to check continuity. It’s good all the way to MAF pin. Re-did PCM and MAF ground about 2 years ago. Checked them now and still good.
I do have wiring diagrams. I’ve talked to two local shops and they don’t want to touch it. May have to reluctantly take it to dealer. Thanks.

Disconnect sensors that shares the same 5V and does it goes back to 5V?

You should post up the wiring diagram.

 

[Laga77]

Disconnect sensors that shares the same 5V and does it goes back to 5V?

You should post up the wiring diagram.

Can’t get under car to check O2 sensors. Only did FP and TBPS without success. I’ll post diagram later.

 

[BC1]

I suspect wiring was damaged or routed wrong during the tranny swap. Could be smashed between the bellhousing and the block. Some grounds were left off...melted on the headers etc. Can you look with a mirror or scope?

 

[clinebarger]

5 volt reference is a misnomer in this application.....

The PCM sends out a 5 volts through a resistor on the MAF Signal circuit, You have to unplug the MAF to get a 5 volt reading.....The MAF will pull the circuit down to zero with it plugged in & no airflow across the hot wire.