if you are still trying to fix this, it's likely a bad glow plug. I would suggest to get an OBD reader that will give you the correct code. It will come in handy with an newer vehicle especially with us CRD owners.
Same thing happen to mine that started with a bad #5 glow plug, for me it's the on in the middle at the left engine side or the driver side. Replaced it with a Bosch Glow Plug for $35 at VAP (dealer wants $80 each) and 3-4 weeks later the engine light came on again with a glow plug module code. I had no choice but to replace it as it was a dealer item at $350 and erased the code and it has been fine since.
Love the torque with this engine but we must deal with the minor hick up as they age, good luck with it