Did I buy a dud?

[Clarkcj]

Hi everybody, absolute noob here, recently purchased my first proper car and it was a 1.9 tdi se 130 Seat Leon.
I love everything about the car, it runs like a dream most of the time there's just one major problem...
Sometimes I can be cranking the thing for a good 10 seconds for it to start and as a result I keep getting these error codes thrown up:
P0605 and P0726.
I got the codes from this clip on fault code reader from a friend and I've done a bit of research but found nothing of any use.
I've also replaced the crank sensor at a cost of £70 which did nothing, I'm a student so that kind of money isn't easy to get hold of!
Any help off you guys would be much appreciated,
Regards,
Christian

 

[AndyBees]

P0726

- Faulty Crankshaft Position (CKP) Sensor
- Crankshaft Position (CKP) Sensor harness is open or shorted
- Crankshaft Position (CKP) Sensor circuit poor electrical connection
- Communication error between the Engine Control Module (ECM) and Transmission Control Module (TCM)

P0605

Possible causes
- Engine Control Module (ECM) may be faulty
- ECM harness power supply circuit is open or shorted
- ECM harness ground circuit is open or shorted
http://engine-codes.com/articles/codes_possible_causes.php

 

[Clarkcj]

Thanks for your quick reply,
How do I test all of these things?

I've replaced the crank sensor so I can assume that that's no longer faulty.
I've also had a look at the electrical connection and wires etc and there are no obvious breaks.
I'm totally at a loss as to what to do next.
Thanks

 

[Clarkcj]

Sometimes the car will start straight away which leads me to think that it could just be broken wiring - is this correct? Or potentially an ecm that's on its way out? How do I test this?

Also, am I right in thinking that the ecm is in the top of the plenum chamber, just below the middle of the windscreen?

Thanks.

 

[Clarkcj]

Bump please

 

[AndyBees]

Yes, ECM is located roughly in the center behind cowl below the windshield.

 

[dan kerkstra]

check all the grounds clean and retighten them then move on jmo

 

[Clarkcj]

Yeah sorry, what/where are the grounds and how do I check them?
Thanks for your patience

 

[stanz]

Grounds/earths negative side of the battery.