Let me start by saying that I am by no means an expert mechanic. I am a casual DIYer that will research a problem and see if it’s worth fixing myself. If you mention a part, I will probably need to check where it is located if I haven’t touched it before.
I bought my daughter a 2012 Mini Cooper S R56 N18 engine. I was getting an oil pressure code and suspected the plastic guide for the timing chain had cracked based on research. I used a borescope and saw pieces of plastic. Shops in SoCal wanted over $2k to fix the chain alone and I knew there would be more issues once they got into it. I decided to tackle it myself thanks to reviewing a bunch of YouTube videos on the subject.
After tearing the car down to maintenance mode, I discovered the crossover pipe for the water pump was also leaking. I decided to replace the following:
timing chain and guide including camshaft and crankshaft sprockets
oil pump including chain
water pump
thermostat
crossover pipe to water pump
tension pulley
belt
also most of the gaskets involved
cleaned the throttle body
new spark plugs
maybe a few more things that I can’t remember at this point.

Anyway, everything back together except for front grill and frame. I went to start the engine to see if it would start and nothing. It cranks, but won’t kick on. I’m getting 10 codes on my Ancel reader. All seem to be electrical and that was my biggest fear. I can replace parts, but I am clueless when it comes to the electrical codes. I know how to use a multimeter, but I don’t know exactly what to connect where to test if wiring is bad or I did something wrong. The ground wire attached to the valve cover did break off, but I stripped the wire and reconnected it. I believe I did it properly.
I will post pictures of the codes. Any help is greatly appreciated. The car has been out of service in my garage for a few months since I have limited time to work on it, and I really want to get it working for my kid again. I feel terrible on how long it’s taking, but I don’t think I can afford to take it to a shop.

Error codes

More error codes

Even more error codes

 

After completing the job, did you forget to reconnect the crucial ground wire for the valve cover and then cranked the engine? If so, the DME may be damaged. The fault codes for the DME 5V reference voltage unfortunately are consistent with this possibility.

In the meantime, re-verify that valve cover ground is properly repaired and has continuity with the battery ground post. Then fully charge your battery to 12.6V.

 

Thanks for your reply. Much appreciated.
I’m not sure if I repaired the ground wire properly. After your post, I went to check it again by removing the black electrical tape and the terminal connector I used on the bare wire wasn’t exactly intact. So it’s possible the ground wasn’t properly connected.
I’m going to repair it properly and see what happens.
Worst case, if it I did damage the DME, how hard would it be to repair and do you know what is needed? I will also do a Google search on this.

 

As you mention, the first and most important step is to properly repair the damaged valve cover ground wire.

When done:
Fully charge the battery
Connect your scan tool; turn the ignition ON (engine OFF); and clear all fault codes.
Turn ignition OFF and again turn the ignition ON (engine OFF).
Check whether all fault codes immediately return or remain cleared.
If the same codes return, the DME is likely damaged (or a 5V engine sensor wire is shorted to ground).

If the DME is damaged, the least expensive options to explore are (1) have your DME repaired or (2) buy a used DME and have your current damaged DME's data cloned onto the used DME.

Other members here or AI (e.g., Google Gemini) may be able to help you do the necessary research and shopping.

 

So I believe I repaired the ground correctly but is there a way to test the repair? I’m including pictures of what I used to repair and the final product.

I followed your instructions above and the fault codes come back. I’m assuming that means my DME is fried.

I’m not sure on how to check for 5V at the sensors. Where are they located or are we talking about any sensors in general like camshaft sensor? Here’s where my electrical ignorance shows. Do I just clip negative probe to a ground / bare metal and test prongs in sensor wire using the red probe?

Thanks for your help.



Purchased these online to fix the issue.

Crimped and heated.



I took out the DME just to get a look at it.

 

I'm sorry but I disagree with a damaged DME diagnosis based on a faulty valve cover ground. It could be possible but very rare odds in my opinion.

Are the error code still present? Have you cleared the codes and tried again?

The codes you've provided are probabaly dealing with something you've unplugged while doing the repairs. Double check every connector under the hood and look for unplugged wires or damaged connectors, even vacuume houses (lines).

 

The problem could certainly be that the 5V reference voltage is shorted to ground.

However, based on my research of the subject (reading and watching YouTube videos), the frequency of DME damage is extremely high when the engine is cranked without the valve cover ground wire connected. The valve cover ground wire serves as ground for the ignition coils. When you crank the engine with the valve cover ground wire disconnected, the high-voltage spark (tens of thousands of volts) has no path to the engine block. The high voltage seeks the path of least resistance, which unfortunately is commonly the DME control wires and ignition drivers, and instantly fries the internal circuitry. It's a BMW design flaw.

 

How to test the 5V reference voltage source on the connectors for the intake and exhaust camshaft position sensors on the valve cover:

Charge your battery to 12.6V.

Set your meter to read DC voltage. Clip the black meter probe to the battery ground connector. Use the red meter probe to read voltage at the camshaft sensor connectors.

With the Ignition ON, probe pin 1 (blue wire) in the intake sensor connector.

Also probe pin 1 (yellow wire) in the exhaust camshaft sensor connector.

You should read ~4.9V to ~5.1V.

Post your voltage readings.

 

Assuming I did this correctly, my meter readings are way low. I got 0.04 on pin 1 exhaust and 0.15 on pin 1 intake for the two camshaft sensors. Battery at 12.2v. Ignition on but engine off.

 

The codes were cleared and returned several times. I checked the two vacuum hoses I pulled when installing thermostat, and they have been properly connected. All other wires seem to be connected. I was thinking that maybe I knocked something out when I was trying to install that crossover pipe to the water pump, but I can’t find it if I did. I used a borescope but didnt see anything.

 

I meant to add. Seems like pin 1 on your diagram is always the middle pin? When I checked the connector, the blue wire was the right side which had a number 1 on the plastic connector. The exhaust had two yellow wires but I gave the reading from the right most hole which had a 1 above it.
if I was supposed to give the middle connector’s reading like pin 1 in diagram, they were both a little over 7v.

 

If i recall correctly there is a (turbo) vacuume line that runs under the intake manifold next to the crossover pipe. I also think there are electrical sockets near the firewall too in this same area. Might be worth checking.

 

You did the tests correctly, and the 5V reference voltage is clearly missing. However, to increase confidence in your results, consider redoing the voltage tests with the battery fully charged (12.6V).

There's either a short to ground in a 5V sensor or its connector/wire harness (best outcome) or the DME is damaged.

 

If you're interested, some relatively simple electrical tests can distinguish a short to ground in the 5V reference voltage downstream of the DME versus a damaged DME (blown internal 5V regulator).

 

I charged the battery to 12.67V. This time when I hooked probes onto the multimeter with ignition on and engine off, the center voltage was measuring right around 4.9V on camshaft sensor. Does this mean DME is not damaged?
note - I used the center wire on the camshaft sensors for testing since that seemed to be the corr canine from your diagram.

Battery tested

Camshaft sensor intake

Camshaft sensor exhaust




Some pics from under manifold

 

I am interested. Please advise. Thanks.

 

I checked anything I could find and everything seems to be connected including the vacuum hoses. Any other suggestions? Thanks.

 

4.9 volts is great! Keep looking for a connector or something not connected correctly.

 

I checked anything I could find and everything seems to be connected including the vacuum hoses. Any other suggestions? Thanks.

 

I’m getting 11.9V at the o2 sensors. Is that supposed to be 12V or higher? I’m guessing it’s not supposed to be 5V like others.

EDIT

I found this while searching:


For a 2012 Mini Cooper, standard system voltage is $\approx$12.6V (off) and 13.7–14.7V (engine running). Key connectors include 12V at the fuel pump (key ON) and 5V reference signals for sensors like the MAP sensor. Most sensor signals operate between 0-5V, while main harness power is 12V.


Key Electrical Connector Voltages

• Battery/Charging System: 12.6V (OFF), 13.7V - 14.7V (Running).
• Fuel Pump Connector: $\approx$12V (Battery voltage) for 3-5 seconds with key ON.
• Engine Control Module (ECM/ECU): Requires constant, stable 12V supply; 5V reference to sensors.
• Camshaft Position Sensor: 5V supply, 5V signal, and ground.
• Sensor Signals (MAP, Temp, etc.): Typically 0–5V range.
• Oxygen Sensor Heater Circuit:12V.
  

Testing & Troubleshooting Tips

• Method: Use a digital multimeter (DVOM) set to DC volts.
• Back Probing: Insert a probe between the wire and connector seal to measure live circuit voltage without disconnecting.

 

That's great news! With the battery charged to 12.6V or higher, clear the fault codes to see which ones, if any, return.

 

Unfortunately , the error codes came back.

 

Returning to the beginning of your thread with a pointed question:

Do you believe that the engine was cranked with the valve cover ground wire either disconnected or substantially damaged?

If so, the N18 DME has three separate internal 5V regulators/sources:
Rail A: Accelerator pedal & throttle body
Rail B: Camshaft and crankshaft sensors
Rail C: Valvetronic position sensors

You have fault codes for two of the Rails (B & C) but not for Rail A (consistent with 5V measured at camshaft sensor connector and no camshaft sensor codes).

Therefore, the current possibilities are:
1) Short to ground in accelerator pedal or throttle body circuit
2) Short to ground in valvetronic position sensors
3) Damaged DME (blown Rail A and/or Rail C)

 

I think I’m at the point where I need to send the DME in for testing. I just don’t want to have this happen again when / if the DME is repaired / replaced. I repaired the ground to the valve cover. I see the ground connection on the driver side near DME. The ground on the passenger side connected to the engine mount is also good. Not sure if I need to check any other grounds. I also checked them for continuity and I believe those checked out.
Any suggestions on a DME repair vendor? I keep seeing The ECU Pro, but not sure on reviews.

 

Shop around. Two other companies to consider: RPM Motorsports and Precision ECU.

These^ are the two relevant ground wires.

--------------------------------
If you wanted to test whether your DME is bad, here are the tests you would do:

Both voltage voltage tests below are done with the ignition ON.