Hi all, I’m hoping you can help.
 

my 07 Skoda octavia vrs tdi is failing to start. It’s throwing out the fault code PO642. 

The “specialist” who’s supposed to have sorted it has told me 3 times now he knew what was causing it & each time he’s been wrong. 

I’ve a video of what it was doing & his vcds reports. 
 

The first vcds is the original report.

Also attached are 3 further scans relating to fault codes generated when certain sensors are detached. (That was their idea)
 
As you can see that with both the map and fuel temp sensor disconnected the car threw a crank position sensor fault.
 
With the cam position sensor disconnected the car did not spot it.
 
They had started to investigate the loom & the next step would have been to check the wiring diagram to see what common ground this sensor have and then start tracing it in the loom. Not sure if they’re digging down a wrong hole.

 

so is this a common issue?
Has anyone had this happen to them before? & how did you solve it? 

It's likely with the age of the vehicle a wire has chaffed or a connector oxidised.

I could be leading you up the garden path, but looking at your freeze frame data, you can see a lot of 10.85V stored when the fault occurs.

If that value is your battery, then it's knackered and will be too low to supply a health Voltage to the control modules.

 

Can you elaborate on how the fault occurs, meaning what are you doing and what do you experience.

Example: "I leave the car overnight, try to start and it just turns over and doesn't fire, after a few tries it does and then runs rough"

Thanks for the replies. 
 

So we’ve got slow acceleration, loss of power, irregular idling, engine hesitation/ jerking when accelerating, my fuel consumption is high & my check engine light and the sometimes stalling. I’ve also got an absolute stench from the exhaust.
 

that’s when it starts. It feels like the engine doesn’t want to “catch” on turn over. 

Thanks for providing extra information.

Do you have the full log of faults?  As I can see errors are elsewhere in the car, and anything could be of use.

 

That smell could be DPF if equipped trying to do a regen.

 

Are you able to get the battery health checked somewhere?

 

There's a list of VCDS users on the forum that you might want to locate someone to help scan/see live data and do some testing.

Yeah I assumed it could be the dpf. 
 

the first 2 vcds reports (pictures) I posted we’re the fault at rest. The others are when we started unplugging sensors to check the ecu was registering them properly & also to see if the initial low vault code disappeared if we found the correct sensor. 

If you can wipe a rag/kitchen tissue around the inside of the tail pipe, it shouldn't in theory be very sooty.

 

On some cars they can collapse iirc, so blocking the pipe potentially.

 

It will be good if you can test that car battery to see if that is healthy, best of luck!