No Ground at MAF

[Laga]

I’ve been dealing with family and health issues and not driving my 2005 GT a lot.
I took it out for a run and it stumbled at about 100mph under WOT. No active codes but I checked stored codes and it had P0340. PA alternator is working fine.
Before this happened, I noticed the a/f was running lean. At one point, the Interceptor gauge was stuck at 19.9. They are not the most reliable. Recalibrated, at it was at high 14’s.
Last week I changed plugs. It’s been over two years and with the SC it was due. Plugs looked normal. Took the car out to dinner and on way home when I went 50% throttle, it started to shudder.
I double checked all wires and air filter since I cleaned that also. It’s a dry Amsoil filter. Cleaned MAF, and looked up how to test with multi-meter. It is getting 12V constant power with KOEO, but when I checked for continuity for ground, I couldn’t find any. I peeled back tape to get to main wire harness, cut insulation as shown in photo, and with KOEO, neg lead hooked to neg terminal, the positive probe does not beep when I touch the black wire with white stripe. It will beep if I touch good ground source. Does anyone know where that wire goes, and what to test next?
Car will start and run great if driven easy.

 

[JC SSP]

Can you data log? I would say TPS but without a hard code Your just replacing parts.

 

[GlassTop09]

I peeled back tape to get to main wire harness, cut insulation as shown in photo, and with KOEO, neg lead hooked to neg terminal, the positive probe does not beep when I touch the black wire with white stripe. It will beep if I touch good ground source. Does anyone know where that wire goes, and what to test next?

That blk\wht wire is the 12v MAF hot wire ground.........it is grounded to the body at G102 thru connector C110 according to the 2005-2010 FWM wiring diagram so if I'm taking a guess, I'd check every body ground around the PCM for this blk\wht wire............or run this wire to another body ground to test it.

Don't have access to pinpont the connector\body ground location thus I'm assuming that this ground wire runs back thru engine harness & grounds in the vicinity of the PCM.

Hope this helps.

Update: Just checked under the hood on my Stang.........that blk\wht wire is grounded to radiator core support by the PCM thus this location has to be G102........
There are a couple of splice joints shown along this wire at S108 & at S115 so I'd think that at least 1 of these has failed...........exactly where in the harness S108 is I can't say but I'd like to think that S115 is the same spliced ground at G102 (there is another blk wire crimped in the same ring terminal w\ the blk\wht wire).

 

[Laga]

That blk\wht wire is the 12v MAF hot wire ground.........it is grounded to the body at G102 thru connector C110 according to the 2005-2010 FWM wiring diagram so if I'm taking a guess, I'd check every body ground around the PCM for this blk\wht wire............or run this wire to another body ground to test it.

Don't have access to pinpont the connector\body ground location thus I'm assuming that this ground wire runs back thru engine harness & grounds in the vicinity of the PCM.

Hope this helps.

Update: Just checked under the hood on my Stang.........that blk\wht wire is grounded to radiator core support by the PCM thus this location has to be G102........

 

[Laga]

Electricity is not my best subject. I will check those locations.
If the ground locations are good, and it appears to be a break in the wire. Would splicing and running a separate ground wire be a possibility?
I appreciate all the help.

 

[GlassTop09]

Electricity is not my best subject. I will check those locations.
If the ground locations are good, and it appears to be a break in the wire. Would splicing and running a separate ground wire be a possibility?
I appreciate all the help.

Yep.......that's the alternative next step if the potential break in the harness can't be located & repaired.

PS edit--The reason why this wire is grounded in the vicinity of the PCM is to reduce\prevent a ground offset since the 12v+ MAF hot wire power comes out of the PCM itself.......not from the BEC. So, it would stand to reason that you would also run another ground wire & terminate it in the same vicinity for the same reason........if you end up doing so.

FYI................

 

[Laga]

Friend, I owe you a cold one. It was right where you said it would be. I will fix it tomorrow as my back has had enough for today. Thank you very much. The one on the bottom,you can see break in the wire

 

[JC SSP]

Thats why this forum is the BEST!

 

[GlassTop09]

Friend, I owe you a cold one. It was right where you said it would be. I will fix it tomorrow as my back has had enough for today. Thank you very much. The one on the bottom,you can see break in the wire

View attachment 98349

You know................come to think of this, I'll also bet that the other blk wire IS the PCM 12v- ground wire off the board.............

You may have just averted another potential issue since the other blk ground wire is also showing corrosion issues........so if I may make a suggestion.........I'd really clean that ground termination point on the rad core support after repairing both wires & apply some dielectric grease to prevent this from happening in the future..........even though this took 19+ yrs to develop.

No problem Laga, glad to be of some help to you.

 

[Laga]

Absolutely, I’m going to replace those two ring contact's along with two others I have for aftermarket accessories I have installed. I’m going to use heat shrink contacts with glue on the inside for a weather proof seal. After sanding down to bare metal, I like to use a conductive grease only on all my ground points. It’s messy if you over do it, but I’ve found it works great.

 

[DieHarder]

Absolutely, I’m going to replace those two ring contact's along with two others I have for aftermarket accessories I have installed. I’m going to use heat shrink contacts with glue on the inside for a weather proof seal. After sanding down to bare metal, I like to use a conductive grease only on all my ground points. It’s messy if you over do it, but I’ve found it works great.

Laga, did this fix your shuddering problem? I recently changed out plugs due to a misfire (first time I've ever had that) which fixed the misfire but found that the engine would shudder at anything above 30-40% throttle under boost. If I baby it (stay out of the boost; less than 25% throttle) she runs fine. So far I pulled the plugs again; cleaned/rechecked everything but haven't taken it on a test drive yet. COPs are less than a year old. No codes by the way but will recheck w/my SCT tomorrow to see if anything comes up. I have a similar setup to yours (06 with DOB kit and M122).

If I still have the shudder under load I'll check the MAF wiring next but wanted to ask exactly where are the wires in your last pic? Can't tell where in the engine bay from the pic. Can you zoom back a bit? Thanks

 

[Laga]

No it did not. I am still chasing electrical gremlins.
Lito is helping by sending a tune where I can replace the MAF with a stock one that I still have. This will test to see if there is a problem with the circuit somewhere else.
The wire location is next to top radiator support on passenger side. Disregard wires on left hand side. Those are to accessories.