Airbag light and Limp Mode

[jono12345]

I have a 2015 mustang GT (5.0, 36,XXX miles) which just starting having issues with the airbag light and going into limp mode.

About a month ago the I was driving the car and the service wrench came on, car went into limp mode, and the airbag light came on (solid light, no blinking).

I just replaced the springs with DMR SP080 about a month before this issue (battery was not disconnected). Car also has a ford racing X pipe and Roush axel back (been on for years).

This issue would happen intermittently at first and the limp mode/airbag light would reset after the car is restarted. I visually checked all the fuses and connections under the seat for looseness. Everything seemed fine. When limp mode comes on the car could still drive but has almost no power. Car has not been in a wreck.

I drove the car about a week ago with no issues, then it happened again. This time the wrench light and airbag light goes off with just a touch of the throttle. Once this happens the throttle no longer works and I can depress the gas all the way and the car will just idle with no increase in revs. Once I turn the car off and on the lights are cleared but will happen as soon as I touch the gas again. There is no check engine light illuminated at any point.

I can turn the car on and it will idle with no lights at all until the gas is pressed.

I was going to drive it to get the codes read but now I can't drive it and will need to have it towed.

I have searched through the internet/forums for this issue but haven't found anything thats quite the same.

I also just noticed that by air pressure display is no longer reading, its just dashed lines for all 4 tires (I don't know if this is related).

Any thoughts on what this could be before I have it towed to a shop to be looked at?

thanks

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[Elp_jc]

Start by pulling codes with FORScan, and then come back. No sense in trying to guess what could be wrong without knowing exactly what is affected. There are like 8 airbags on our cars now, and they're all over the car, so you need to know which one is acting up to begin with. And also what other codes (if any) could be. Good luck.

 

[jono12345]

Alright so I purchased the FORscan unit and read the current DTC codes on the car. See Below.

P0532
P0533
P0A5A
P0A5B
P2122
U0401
B00A0: 68

The first two codes I know what is causing them because my refrigerant sensor is unplugged.

I used the FORscan to clear the DTC codes, I drove the car down the street the car went into limp mode and they all came back so obviously something needs to be looked into.

P0A5A and P0A5B are both for a generator current sensor which I've read can affect the body control module. I thought I saw somewhere that the body control module can be associated with airbag sensors? I should probably check the voltage on my charging system.

I performed the re-configuration process for the OCS and RTM systems and the FORscan says that everything is working as normal.

Any thoughts on what to tackle first? Or how to better use the FORscan to get deeper into the route cause of the problem.

thanks

 

[Cobra Jet]

Just curious - have you removed the battery lid and checked to see if the terminals or ends of cables are corroded?

 

[jono12345]

The terminals looks clean. There is one ground that I can see that has a little bit of green that I'll probably take off and clean.

 

[fatbillybob]

There are like 8 airbags on our cars now, and they're all over the car,

Not only that but modules to the ECU and sensors all over the place. But I am puzzled by the limp problem. My car is a 2019 new car converted to a racecar. My airbag ligth has been on since about day 2 and all my crash sensors are gone as well as all the airbags. The modules are still there only because I wanted to get on track and remove them to make sure I got no weird limp feedback. That said with my system defunct I get only the airbag light and no limp. I'm racing my car 10/10's without issue. I'm even a paddle shift automatic.

 

[jono12345]

Yeah im thinking the limp mode is probably coming from the p2122 for the throttle position sensor. I'm going to check the voltage from the charging system and see what its putting out today.

I do remember about a week before this happened I had a weird idle issue where it sounded like the car had choppy idle almost like a ghost cam tune. That only lasted for a minute or two and then went away. Not sure if that is related.

 

[jono12345]

So I let the car sit with the negative terminal off for about 4 days. During this time I disconnected and reconnected the current sensors. When I turned the car back on and cleared the old codes I only got one code for the power steering control module. I ran a test on this module and the code changed and turned into code U0415 for the ABS.

The car seems to be running and driving fine now, but has anyone had these issues where the codes seem to be jumping around?

 

[jono12345]

Just to put this out there. The problem was found. The A/C sensor plug was worn/chewed through causing a short. See pic below.

 

[Elp_jc]

So an A/C sensor was causing all the other faults, including limp mode??? Damn; that makes no sense. But good to know that could happen. Now take care of your rodent issues .

 

[fatbillybob]

Do you need that part where it is cut from the harness further up? My car is a racecar and I do not need that connector. I'm sure it is orphaned in my 2019
GT

 

[jono12345]

Yeah, I didn't think this would be the cause of all the faults since it was for A/C pressure but I guess so. I actually found another post here from a while ago that had this same plug causing throttle position sensor faults (wire was rubbed through).

FatBillyBob - I ended up just purchasing the plug head and splicing it in so I'm all set, but thank you.

 

[Deep4k]

I have the exact same problem on my 2015 mustang GT pp… except it’s not my ac plug because I checked it as well as all the wiring around the engine bay and everything seems fine. Battery connections are good (clean and tightened). The problem comes and goes with there being no real way to make it pop up or really diagnose. Codes are u0151, p0532, p2122. Ac doesn’t work even though it’s filled… I’m thinking that’s it’s own problem since it’s been like that before this limp mode issue started and compressor also makes a whining noise which is common on this platform from what I’ve read. Any help is appreciated thank you.

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