BTW there are several different P0670 fail codes.
Most OBD computers only show 1 code as they dont show the extra digit e.g. P06701

My cheap OBD shows the description though "open circuit".


Here are the basic codes in German
17054 429E P0670 Gluhzeitsteuergerat 1,Gluhstromkreis elektrischer Fehler im Stromkreis
17055 429F P0671 Gluhkerze Zylinder 1-Q10 elektrischer Fehler im Stromkreis
17056 42A0 P0672 Gluhkerze Zylinder 2-Q11 elektrischer Fehler im Stromkreis
17057 42A1 P0673 Gluhkerze Zylinder 3-Q12 elektrischer Fehler im Stromkreis
17058 42A2 P0674 Gluhkerze Zylinder 4-Q13 elektrischer Fehler im Stromkreis
17059 42A3 P0675 Gluhkerze Zylinder 5-Q14 elektrischer Fehler im Stromkreis
17060 42A4 P0676 Gluhkerze Zylinder 6-Q15 elektrischer Fehler im Stromkreis
17061 42A5 P0677 Gluhkerze Zylinder 7-Q16 elektrischer Fehler im Stromkreis
17062 42A6 P0678 Gluhkerze Zylinder 8-Q17 elektrischer Fehler im Stromkreis
17063 42A7 P0679 Gluhkerze Zylinder 9-Q18 elektrischer Fehler im Stromkreis
17064 42A8 P0680 Gluhkerze Zylinder 10-Q19 elektrischer Fehler im Stromkreis
17065 42A9 P0681 Gluhkerze Zylinder 11-Q20 elektrischer Fehler im Stromkreis
17066 42AA P0682 Gluhkerze Zylinder 12-Q21 elektrischer Fehler im Stromkreis
17068 42AC P0684 Gluhzeitsteuergerat 1=>-J179 unplausibles Signal



From a Chevrolet manual I found the full codes (it uses the same/similar glow plug module)

DTC P064C (00): Glow Plug Control Module Performance
DTC P0670 (01): Glow Plug Control Module Control Circuit (Short to Battery)
DTC P0670 (02): Glow Plug Control Module Control Circuit (Short to Ground)
DTC P0670 (04): Glow Plug Control Module Control Circuit (Open Circuit)
DTC P0670 (54): Glow Plug Control Module Control Circuit (Temperature High)
DTC P0671 (02): Glow Plug 1 Control Circuit (Short to Ground)
DTC P0671 (04): Glow Plug 1 Control Circuit (Open Circuit)
DTC P0672 (02): Glow Plug 2 Control Circuit (Short to Ground)
DTC P0672 (04): Glow Plug 2 Control Circuit (Open Circuit)
DTC P0673 (02): Glow Plug 3 Control Circuit (Short to Ground)
DTC P0673 (04): Glow Plug 3 Control Circuit (Open Circuit)
DTC P0674 (02): Glow Plug 4 Control Circuit (Short to Ground)
DTC P0674 (04): Glow Plug 4 Control Circuit (Open Circuit)
DTC P0683 (00): Glow Plug Control Module Communication Circuit
DTC P0683 (3A): Glow Plug Control Module Communication Circuit (Incorrect Component Installed)
DTC P0683 (71): Glow Plug Control Module Communication Circuit (Invalid Serial Data Received)
DTC P161E (00): Glow Plug Positive Voltage Circuit


Full reference here for the meanings of these codes:
Service Manual2007 Captiva Diagnostic Trouble Code (DTC) P064C, P0670, P0671, P0672, P0673, P0674, P0683, P161E


So the glow plug module computer was still working as it was getting power, but the voltage would have been below 8.5V which is the trigger for open circuit.