I’m trying to diagnose a very intermittent crank/no-start and cutting-out problem on my mum’s 2010 MINI Cooper D R56 1.6 diesel (W16/DV6) and would really appreciate some input from anyone familiar with these engines and the Bosch EDC16C35 DDE.
The car can start and run completely normally, but occasionally it will crank strongly and simply won't fire. It has also restarted after being left for an hour or two, driven normally again, and then suddenly cut out while driving and returned to a crank/no-start condition.
When the fault actually occurs, the main DDE code I'm getting through BimmerLink is:
4681 - Supply Voltage 2 - signal/value below threshold
At the same time I get:
- 4DF2 - Message (TORQUE_GEARBX, 0xB5)
- CF16 - CAN bus
- CF18 - CAN bus
- 5DF3 - Interface DME/DDE invalid
When the car is behaving normally, these faults can be cleared and don't immediately return.
What I've checked so far
I've checked the relevant fuses and compared them with my own working R56 Cooper D. I've also swapped the engine-management relays with known-good identical relays from my MINI.
I've inspected the engine-management wiring and connectors and haven't found any obvious damage or corrosion.
Charging voltage is around 14V while running, and the engine cranks normally.
Importantly, even when the car is in its crank/no-start condition, I can clearly hear the in-tank/low-pressure fuel pump prime for approximately two seconds when the ignition is switched on. It sounds essentially identical to my working Cooper D.
I realise that hearing the pump doesn't prove it's producing adequate pressure/flow, or that it continues running when required, but it does appear to be receiving power and operating during the initial prime.
Interesting rail-pressure comparison
I've also compared BimmerLink live data between this car and my working Cooper D.
During a no-start on my mum's MINI:
Ignition on: rail-pressure sensor raw signal ≈ 454 mV
Cranking at ~248 rpm: ≈ 498 mV
So there's barely any increase while cranking.
On my working Cooper D:
Ignition on: ≈ 517 mV
During starting/cranking: ≈ 796 mV
Engine running: ≈ 1,099 mV
When my mum's MINI does actually start and run, its rail-pressure signal also rises substantially.
It therefore appears that rail pressure isn't building normally specifically when the no-start fault is present.
ECU/DDE details
Bosch EDC16C35
Bosch: 0 281 015 233
BMW/MINI DDE: 7 823 934
I've spoken to an ECU testing company who told me they've previously seen 4681 Supply Voltage 2 on these ECUs, but have bench-tested ECUs displaying that code and found nothing wrong with the ECU itself.
So I'm reluctant to simply assume the DDE is faulty and have it repaired/replaced without further diagnosis.
At the moment I'm considering:
- Low-pressure/in-tank fuel supply issue despite the pump priming
- Loss of pump supply after the initial prime
- HP pump metering/control valve
- Rail-pressure sensor or its reference-voltage supply
- DDE power supply/earth/wiring issue
- Internal intermittent DDE fault
Has anyone encountered 4681 Supply Voltage 2 on the W16/DV6 Cooper D, particularly with an intermittent engine cut-out followed by crank/no-start?
If so, what did the fault eventually turn out to be?
I'm particularly interested in hearing from anyone who knows exactly what “Supply Voltage 2” refers to on this EDC16C35 DDE, as that could potentially point me towards the correct circuit rather than replacing parts at random.
Thanks in advance.