At the APP1 & 2 (pin 1 and 4) I’m getting close to zero. At the intake pressure sensor blue wire, I’m getting 4.8V under the conditions for testing.
does that still mean DME is bad? I believe I did tests correct. Black wire on intake pressure sensor test was connected to ground on valve cover. For the APP, I used the pedal rod exposed metal as a ground.

 

From my googleing....

Mini Cooper R56 DME (Engine Control Unit) failures typically manifest as a crank-no-start condition, total loss of communication with scan tools, and severe engine misfires. Other symptoms include sudden limp mode, heavy power loss, or complete stalling due to ignition/injection failure, often triggered by voltage spikes or water damage.

Key Symptoms of R56 DME Failure:

• No Communication: OBDII scanners cannot connect to the DME.
• Misfires & Rough Idle: Continuous or intermittent misfires (often Cyl 2 or 3) that do not improve with new spark plugs or coils.
• Limp Mode/Power Loss: Sudden drop in power, stalling, or inability to accelerate.
• Error Codes: Multiple, inconsistent fault codes (e.g., "internal failure" or "no coding").
• Locked CAS System: CAS (immobilizer) and DME mismatch, preventing ignition.

Common Causes:Immediate Troubleshooting Steps:

1. Scan for Codes: Look for ECU communication issues.
2. Check Ground Cables: Ensure ground bolts are tightened.
3. Inspect for Water: Check the DME box for moisture.

• Crank, No Start: The engine cranks but will not start, often accompanied by code P167F.
  • Voltage Issues: Jump-starting with a dead battery can "brick" the DME.
  • Water Damage: Water entering the DME box under the hood.
  • Internal Faults: Overheating or damaged circuits within the module.

 

The pedal rod may be insulated by grease or plastic bushings, so it could potentially yield a false 0V reading. For confidence, repeat the APP1 and APP2 voltage tests using a known good chassis ground (strut tower bolt or even better the (-) battery post). If you read 0V using one of these grounds, the DME is damaged.

The wire to test in the intake pressure sensor connector is gray with a blue stripe (gray/blue). Testing a different wire (e.g., yellow/black or yellow/blue) would potentially lead to a false 5V reading. For this test, use the (-) battery post for ground.

 

I ran another test on APP pin 1 & 4. Connected the black to negative battery post. Readings were 0.011V on both. Did another test intake pressure sensor. The blue wire showed 7V this time. The white wire showed .0009V.

 

Unfortunately, both tests confirm DME damage to internal DME rail A and rail C. 0V at APP1/2 (rail A) points to a blown internal voltage regulator. 7V at the blue wire of the intake pressure sensor likewise indicates a damaged rail C because the 5V reference voltage should never be above 5.5V-6.0V. This could be caused by an internal DME short that leaks 12V into the 5V rail.

Be aware that the abnormally high 7V on rail C may collaterally damage sensitive 5V sensor electronics (e.g., intake pressure sensor, Valvetronic position sensor, or even the accelerator position sensor). This would become evident by seeing fault codes for these sensors after installing a repaired or cloned replacement DME.

 

Hi. Here’s an update. I sent the DME / ECU to The ECU Pro for testing and repair. Cost was $399. Here is what the tech said:

“Greetings,

I took a look at your equipment and found that a component on your DME, which would cause exactly the problem you reported, was damaged. I replaced the component and was able to subsequently start our test vehicle with your equipment connected. Attached is a video of your equipment running in our test vehicle without issue. The fault code in the video is expected due to differences between your vehicle and ours.

Your equipment will ship today via two-day shipping. I couldn't say exactly what caused the failure, but since the component was blown internally it was probably some kind of voltage spike.”

My follow up question for this thread. How do I make sure that all grounds are good before I reinstall the DME and attempt to start the car again? don’t want another voltage spike blowing it out again. I’m assuming I test the 5V and 12v pins again to see if voltage is correct. If you can think of another foolproof way to test, please let me know. Thanks.

 

Congratulations on the successful DME repair!

You are very wise to test the valve ground wire before reinstalling the repaired DME.

Conducting a voltage drop test on the valve cover ground wire is the only way to know whether the DME can be safely installed in your car.

The voltage drop test must be done with the circuit under load, so you obviously cannot safely use the normal coil load to test the ground as this would damage the repaired DME if the ground is bad.

This means you must place the ground wire under an artificial load having similar amperage as the coils without the DME installed. The high-beam element of a H13 incandescent headlight bulb produces a similar load. For the test, the outer high-beam power pin of the H13 bulb is soldered to a 14-gauge stranded copper wire that will be connected to the battery (+) post and the center ground pin of the H13 bulb is soldered to a different 14-gauge stranded copper wire that will be connected to the valve cover ground stud.

To conduct the voltage drop test:
1) Secure both the (-) bulb wire and the valve cover ground wire to the valve cover ground stud.
2) Secure the (+) bulb wire to the (+) battery post. The bulb should shine brightly.
3) Set multimeter to read DC volts.
4) Touch one multimeter probe to the engine head near the ground stud and the other multimeter probe to the (-) battery post.
5) If the valve cover ground wire is good, the multimeter reading should NOT be higher than 0.1V.

 

Ground test diagram

Does my diagram look accurate? How do I know which pin is power and which is ground on the bulb? Can you give me an example of where to put second probe from multimeter when you say “engine head”? Thanks.

 

Your voltage drop diagram is excellent. In my recreation, I added the key downstream ground points that you would need if the first voltage drop test is >0.1V.

For first voltage drop test, touch one multimeter probe to the metal ring terminal (eyelet) of the brown ground wire and the other probe to the center of the (-) battery post.

 

Do you have non-xenon H13 headlight bulbs? If so, you should be able to identify the bulb's (+) high-beam pin and ground pin by plugging the bulb into the headlight connector. The bulb's (+) high-beam pin will correspond to the yellow/blue wire and the ground pin will correspond to the brown wire.

 

At first I was getting a reading above 0.01V. In this picture, it’s 0.019. However, I think my connection of multimeter probe to ground wasn’t secure.

 

Better attachment onto valve cover ground pin with multimeter probe. Reading was 0.005V.

I also connected multimeter probe to the engine mount bracket where the other ground is located. Reading was under 0.01V. It was about 0.005V.

 

So I’m a little worried that my results may be inaccurate since I’m using banana clips instead of soldering. I was just testing to see if it would work. I can still do the solder if needed and more accurate. Also, I did get two different results connecting the probe to the valve cover ground pin. I was about to stop my test and believe the valve cover ground was not good, but when I tried it again, result was under 0.01V. Can I trust it?

 

Very promising. If you can reproducibly get <0.1V voltage drop using banana clips, the ground is good. Repeat the test multiple times until your voltage drop readings are convincingly 0.1V or less. The bulb seems to be glowing brightly.

 

I finally had some time to start putting things back together. I connected the DME and then started hearing a clicking sound. The “P” on the gear shifter was blinking to the beat of the clicks. I went to check where the clicks were coming from. There were two locations - the passenger footwell fuse box and the engine fuse / relay box near DME. Any idea why? I’m charging battery as it may have drained some, so not sure if that could be a cause. I’ve circled the two relays that were clicking.

 

What was the voltage across the battery posts?

Your circled component in the JBE appears to be the K96 fuel pump relay.

Your circled component in the A400a front power distribution box is the DME main relay (K6300).

Charge the battery until reads at least 12.6V across the battery posts.

 

Ok. I didn’t read your benchmark correctly. I’m getting reading of 0.024V and I kept thinking it was a problem. Reading your post again, the benchmark was 0.1V and not 0.01V. I got the same 0.024 reading at the valve cover stud as well as at the engine mount ground stud. Let’s see how this goes. Fingers crossed.

 

Correct. Your voltage drop readings have been outstanding.

Is your battery voltage optimal and do the K96 and K6300 relays continue to click?

 

No more clicking after I charged the battery. Battery may need replacement because after charging, it drops below 12V pretty quickly. Not sure if that’s a sign to replace.
I put all connections back together and tried to start the car. It only cranks and won’t turn over. I’m getting the error codes for “hot film mass meter”. I don’t see any issue with that part and never got that code before. 🤦🏻‍♂️. any thoughts on this new error and why engine won’t turn over?

 

Seems like now I’m getting random errors.


Now getting this error about rail pressure.

 

Both the MAF sensor and fuel rail pressure sensor share the same DME 5V rail. When your DME was damaged, the abnormally high voltage present on this 5V DME rail may have damaged both sensors. Code 002BF2 is preventing the engine from starting.

Do this test:
1) Turn off the ignition and disconnect the (-) battery connector.
2) Unplug both sensors.
3) Reconnect (-) battery connector.
4) Charge battery to 12.6V, if necessary.
5) Try again to start the engine.

This test may be followed by a couple of voltage tests, depending on the results.