I have a 2013 MCS with no spark on Cylinder 4. P0304 code so I replaced coil and plug. Same result. I hooked up a test light to the between the new coil and plug installed in #4. No pulse. I switched the wire from the top of #3 to the coil and plug on #4 -- I got a pulse. Basically I'm not getting any signal from the computer to fire #4. Checked compression all are good. It will start and run on three cylinders. Its an automatic transmission.

Other than a wiring short or computer failure - what could cause one cylinder to have no spark?

What tells the computer when to fire #4?

cam or crank sensors?

Would this cause only one cylinder to not fire or all cylinders?

Is there a place to test for signal from the computer closer to the computer to rue out a short? what voltage comes from the computer to the injector 12v -- would it activate a test light? A wiring diagram I found shows it to be an orange wire at #28 from the dme/ecu to the #4 injector. This looks to be consistent with the orange wire a see at #4.



thanks for the help.



Heath

 

Likely a wiring issue or faulty DME.
With the ignition on, check for 12V on the green wire that connects to the coil.
Check for continuity on the orange wire that runs from the coil to the DME.
If everything checks out then it's probably a bad DME. The FETs inside it that fire the coils can sometimes go bad.

 

Harness ? https://www.realoem.com/bmw/enUS/sho...diagId=12_1399

 

Thanks for all the replies ---

Confirmed 12v on the green wire at all coils. Checked continuity on the orange wire from the coil connector to the computer connector. It is good and verified resistance is same as cylinder #3.

Question --- is there something that would tell the computer to not fire #4 if the injector is out? only code i have seen is a p0304 cyl 4 misfire. It is stored as a permanent code (i think they reset after 100 miles or so of normal driving). My code reader is generic and not mini specific.

Considering buying 3 more coils as recommended above. might get a code reader that will read mini specific issues. any recommendations?

 

Perhaps, but I'm not entirely sure.
Definitely scan it with a BMW/MINI specific reader. They can often sniff our errors that generic readers will miss.
I'm using ISTA-D with a DCAN cable. It works great but it's not for everyone - there's a steep learning curve.
I don't think buying more coils is going to do anything for you. There's no indication that anything is wrong with them.

 

follow up --- it was a bad dme. bought a junkyard dme with matching numbers for $80. took it to a guy in Dallas who had a video on YouTube of cloned dme. $295 later and it fired right up with no issues. I did have to clear some codes.

 

Great thread!
Which numbers on the DME did you match up?