[green grass]

Symptoms

"Drivetrain malfunction, drive moderately" error occasionally on startup every few weeks, but then behaves perfectly normally. Error only appears on startup, and clears spontaneously after a few miles. The error never appeared with stop/start (although I've disabled that as a caution) and has never appeared while the car is driving. The following codes appear:

• 1B5202 - Terminal 15N_1: no voltage
• 1B5302 - Terminal 15N_2: no voltage
• 1B5402 - Terminal 15N_3: no voltage
• 130002 - VANOS solenoid valve inlet, control: short circuit to ground
• 130202 - VANOS solenoid valve outlet, control: short circuit to ground
• 122002 - Diverter valve, control: short circuit to ground
• 1C0202 - Engine oil pressure control valve, control: short circuit to ground
• 120408 - Boost pressure control: shut down as a follow-up reaction
• 12B102 - Lambda probe heating after catalytic converter, control, short circuit to ground
• 102A01 - Air mass meter, signal:electrical fault
• 1D2402 - Map thermostat, control: short circuit to ground

Battery is new, car is essentially stock.


Solution

Replace Integrated Supply Module/Power distribution module, BMW part number 12638645514

Around $100 from the usual suspects, or $30 from fleabay. I went with new due to uncertainty, were I to do it again, I'd buy a used one.


Replacement notes

• The part is located in plain sight on the wall of the engine compartment on driver's side strut tower
• You actually remove the PDM/ISM carrier from the car, and then snap out the module. The snaps are pretty stiff, best to use a plastic pry tool or a screwdriver.
• It's hard to get the bottom electrical connector locking clip off in-situ, and much easier to remove the module and then pick at the connector.
• This took me half an hour because I was being really careful with the weak plastic clips and used locking pliers and picks. If you've got better hands than I do, it's a ten minute job

Idle speculation

In any other car, I would guess this is a starter relay fault. Terminal 15N is post-start ignition on, and my guess is that the starter might be drawing too much power, causing the DME to brown out, causing all the above random shorts.

Terminal 15N is switched by the ISM/PDM, forward electronics/fuse box, and aft electronics/fuse box. I started at the source (ISM/PDM), and the error has not reoccurred in six months.

A similar (although weather-related) problem on X-series BMWs of similar vintage

[Waltabeast]

Hi OP. Did you have start up issue? My car has no issues starting or driving but i recently got the 1B5202 – Terminal 15N_1: No voltage code. Do you recommend I swap that same part you did?

[green grass]

Waltabeast: Depends. I wouldn't throw parts at a mostly working car, as that could cause more problems than it fixes.

Do you get any other codes? Replacing that part makes sense if you're having trouble switching everything on terminal 15N.

[Waltabeast]

These are the 4 codes i have. I do have a catless down pipe but i don’t think the terminal is related.

12B302
Lambda probe 2 heater Bank 1, activation: Short circuit to ground

12B102
Heating lambda probe 1 bank 1, activation: short circuit to ground

138104
Exhaust flap actuator, signal line: open

1B5202
Terminal 15N _ 1: no voltage

[Waltabeast]

Bump. Anyone?

[AlejandroRuiz]

Hi i have the codes 1B5202 12B302 12B102, i change the ISM module and the codes doesnt erase!!! Please Help!!!

[FREE100KSECRET]

Curious, is there a way to diagnose the Integrated Supply Module/Power distribution module, BMW part number 12638645514 or do you have to replace it. I am getting a crank for a second, then dies, so is there a point to see if it is getting power.
Thanks,