Poorly C5 (2006 hdi auto)

[Harlequin]

Was pottering around town when the C5 (2006, 138bhp 2 litre hdi, 6 speed auto) came to a halt , lots of dash lights and `gearbox faulty`.

Tried resetting ecu, but nothing at all. RAC brought it home of a flat bed.

Errors listed are:

RAC DIAGNOSTIC SYSTEM
System Type: ENGINE SYSTEM TEST/VALUES
Name: XFU - BOSCH ME 7.4.7
DTC: P2408,Diesel additive system; defect filler cap sensor or additive level error
DTC: P0401,Exhaust Gas Recirculation Flow Insufficient Detected
DTC: P0500,Vehicle Speed Sensor Malfunction
DTC: P1164,Rail pressure sensor circuit, coherence
System Type: GEARBOX
Name: GEARBOX - AL4 - AT
DTC: 3251,unknown
System Type: GEARBOX
Name: GEARBOX - AM6
DTC: -,Rear left wheel speed sensor
DTC: -,Front wheel speed sensor
DTC: -,Incorrect change to neutral position
System Type: BRAKES
Name: ANTILOCK BRAKING SYSTEM - MK 60 ESP
DTC: -,Rear left speed sensor
System Type: SUSPENSION
Name: AIR SUSPENSION - VALEO
DTC: U1213,Invalid data received from ABS control module
DTC: U1205,No communication with steering wheel angle sensor
DTC: U2005,Triggering (vehicle speed receipt anomaly)

rest fault codes and gearbox came back straight away - the change to neutral one

any ideas? Am thinking Valve Body

[Harlequin]

As an extra - emergency 3rd is not available, putting it in reverse or drive does nothing, it still free wheels. Position lights up (P>R>N>D) and pushing to manual mode lights up 1 - but rev it to move off , it comes up gearbox faulty and manual mode 5 stays lit.

[Jay-Bruce]

This maybe sounds stupid, but have you checked the battery voltage? During lockdown, when the car was only moving once a week, and draining more power than it was generating* our X7 did something similar.

*during lock down our was doing worse than naff all, start engine, drive couple of meters on driveway to access boot, stop engine. Open electric tailgate, load shopping bags, close electric tailgate. Start engine, drive ~1/4 mile to supermarket, electric tailgate open to retrieve shopping bags, electric tailgate closed. Electric tailgate open to load shopping. Electric tailgate closed. Start engine, drive ~1/4 mile home, stop engine. Electric tailgate open unload shopping, electric tailgate closed. Start engine, reverse couple of meters into parking space on drive, stop engine.

[Harlequin]

Will put it on charge - the lexia fault code is P0765, Solenoid D.