The unstable control module voltage is still consistent with an electrical rather than mechanical issue. Can you include the fuel pressure data in the chart?

 

The drops in fuel pressure line up with drop in voltage.

 

That's a strong correlation that confirms that you are chasing an electrical gremlin. Nice work.

 

Test #1
Unplug downstream O2 sensor and then redo your recent test to see if control module voltage stabilizes and fuel pressure stays high. If so, either the O2 sensor is bad or the heater power wire for the O2 sensor is intermittently shorting to ground.

 

Wouldn't that make the car run horribly or since it only is checking the efficiency of the cat would it run ok?

 

Good question. The downstream O2 sensor does contribute to fine tuning the fuel trims. But after you unplug it, the DME will stop using the sensor data, and the engine will still run fine in a pre-programmed mode.

 

ok, would it be possible using ista to see the issue instead? I am also gonna try and throw a piece of electrical tape on the small tear to see if that helps too.

 

ISTA and tape are great ideas.

 

I am gonna run ista prior to tape and after tooth see if it fixes anything I'll let you know what I find.

 

is there anything different i should monitor compared to what you recommended before?

 

No. Those are best for now. Good luck!!

 

So recieved my new cable for ISTA in the mail but have not had a chance to do any data logs with it yet as the weather got really bad around me. I was however flipping through my Bentley manual that I have an noticed that many of the electrical components including the ones I am noticing the issues with share a common ground. I checked resistance with a crappy multimeter from the battery to the engine to check if it was a main grouding strap, it seemed alright but I am gonna recheck it over the weekend. I did notice that all the components go to common ground pin of 31 on the DME. It does not state which connector it is apart of but I know many of the grounding wires go to one of the three connectors. Would you happen to know where the grouding cables for the DME are? I looked in the manual and it told me but was very vague. I am leaning towards being a grouding issues because for a while now, idk if it was around the time I started having the other issues, but when I roll up the windows the rpms drop a little bit and them come back. I know on other cars like my subaru it was a pretty clear indicator of grouding needing to be done.

 

Be aware that Bentley wire diagrams are notorious for errors that can easily take you down a rabbit hole. Your best resource is ISTA because it matches wire diagrams to your VIN.

I have a side project working on R56 DME pinouts, so I'll look into the ground pin you mentioned.

 

I noticed for the most part the Bentley manual has been good at least for me, I'll poke around ista and see what i can find. If you do happen to get the pin out setup definitely would appreciate a copy.

 

Are you referring to the PWM sensor grounds labeled 31 in Bentley DME wire diagrams? The 31 does not represent a DME pin. It refers to terminal 31, which is the common designation for a ground return. With that said, the internal DME terminal 31 ground likely routes to pin 53 (Master Chassis Ground) in DME connector A (X60004) and then to the (-) battery connector via the DME chassis ground (X165) on the passenger strut tower (corrected).

 

Yes I was referring too that but good to know. I will check what the resistance of thise wires are and see if that may be the problem or part of it. I still gotta data log with ISTA which hopefully can be done on my way home from work.

 

 

was able to get a full pin out for the n18s dme. Gonna compile it into an excel file to make it easier for lookup

 

Is this the ISTA pinout for your VIN?

 

I think your N18 DME pinouts interestingly may be for an early European pre-LCI (2010?) N18 Mini Cooper.

What's your Clubman's build date?

 

I beleive so it was the one that came up based off my VIN it is a 2011 N18 US model built in November 2010

 

I did some resistance testing for the grounds and pin 3,4, and 53 for the DME X60004 read at 0-0.1 ohms when checking against the block, but when I tested it to the negative battery terminal it went up to around 0.8 ohms, is that normal? Is it also normal for ground resistnace to increase when the car is in accesory mode?

 

Circuits should not be under a load when doing resistance measurements. Better yet, disconnect the battery.

The DME ground pins will almost always be grounded to the chassis rather than the block, so do your DME ground pin resistance measurements to the chassis and the (-) battery connector or post.

Also, a voltage drop test is the superior method to test for a bad ground connection.

 

I measure the resistnace when they negative battery terminal was disconnected and it was around 0.2 ohms, when I reattched it increased. I can not find the excat locations for the ground on the chasis. I was able to find where the ground from the battery went to and measured good. I did some looking into how to do a voltage drop test, I can not find the best way to do it would you mind giving a quick breakdwon on how it should be done.
While checking around I checked the voltage on the 12v constant and they were reading steady and normal. I did digging in ISTA as well and could not find a way to track the Terminal 87 voltage, is there something else it might called I tried looking for voltage regualtor or anything to track the voltage and could not find anything.

 

Please provide details for how you are doing the measurements, what the meter probes are touching, and all of the readings.

Trace the thick brown ground wire that runs from DME pin A53 to the chassis around the passenger strut tower.

Let's start here. You need a back probe kit like the one shown below from Harbor Freight Tools.
Google Gemini AI response: