fault code: 26--> Control Unit Supply B+

[mino1709]

howsit guys. my m3 refuses to start:nonono:??? checked all the fuses, they fine. ran a diagnostics tingy and picked up fault code: "26- Control Unit Supply B+"
any of u guys had this problem on a 2door e36 m3?
any advice on how to fix this problem? thanx

 

[beezo003]

have you checked the DME?

Do you have spark?

 

[ClassicB]

Does it crank or completely dead?

 

[mino1709]

tanx for the rply bru:thumbs: how do i check that and how will i knw?... the car jus swings... i get a fuel smell... if i let it stand overnight wen i try to start it switches on but then dies almost immediately

 

[beezo003]

it sounds like you not getting spark,do you know how to take spark plugs out?

 

[mino1709]

yes i do

 

[beezo003]

leave the spark plug in,pull the lead out and swing the car to see if its sparking

 

[ClassicB]

Did your battery lose power anytime?

 

[mino1709]

yeah my battery is completely dead. plus it nt even 3months old... i have to jump start it if i dnt use the car for 3days... will check for spark as soon as i get home:thumbs:

 

[ClassicB]

thought as much. Get your battery tested, even though it is 3months old.

Seems to me you have a power supply problem with that error. If you have the incorrect size battery will also add to this.

And if you jumping with a car with a smaller battery/power, it wont start.

What size battery you got?

 

[mino1709]

yeah plus the guy wu done the diagnostics told me sumin about the control unit voltage... it is a size 652....

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few time i had to jump start i used the same 318is im usin nw to jump start and it worked... cud i have not effed sumin up by jump startin the car?

 

[ClassicB]

I think that is your problem.

I will double check on my car, but i think it should be a 658.

If you jump start make sure to put your park lights on and demister, to be safe. Then you should be fine, but i just think your battery is too weak. Even jumping it with another car is not enough. I had a similar problem once, once the battery is too weak it will refuse to start.

 

[ClassicB]

Checked, your battery size is correct...652.

 

[mino1709]

ok so ive checked for spark made sure of the battery power ect.. bridged the power from the fuel pump to the + and car starts...:idea:.... any1 knws what cud b the cause here? cs i dnt tink its wise to b drivin the car like dat haha

 

[beezo003]

did u check fuel pump relay/fuse

 

[mino1709]

the fuses r all 100%. how do u check a relay?

 

[beezo003]

check maybe if u can swop one of the relays

This is e36 diagram i dont know if the m3 is the same

 

[mino1709]

so i sorted out my car, made sure there is spark den found that petrol wasnt cumin through so ran direct power to the pump and it started then found my alarm system was the issue.. cuttin off petrol.. jus nw my airflow meter is nt workin:argh:......

 

[beezo003]

you got an aftermarket alarm system?

 

[oscargxx]

hey guys im a newbie here but I had the same problem on a 92 e34
i had a bad o2 sensor replaced it and after that cel came on code 26 control unit supply votage i checked power on battery 12v good relay 12v alternator 14v when running good power supply at ecm 12 good so i thought after all that that i had a bad ecm replace it and still same code one thing that it will do was when ever i reset the light with the scanner i had a hard starting it it will shut down right away well i found the problem bad mass air flow sensor replace it and code 26 went awayraise: