Alfa Romeo TCT Gearbox - P294D-18 DTC - Diagnosis&Fix

P294D-18 DTC - electro pump unit current too low/below threshold.

This problem occured in my gearbox last time, well it wasn't immediately, it was already throwing this DTC and go to limp mode before but it was occasional.

Before You decide to replace expensive components like whole hydraulic actuator kit or worse the gearbox, you should check only the electric motor of the pump (it's independence from rest) and things related to it like;

  • Condition of battery

  • SDU (Smart Driver Unit, mounted in e.g Giulietta, above the head driver lamp)

  • Relay

  • Fuse

  • Check if there is power at connector output going to the electric motor - 12V.

Also reminder, if you have P294D-18 DTC, sometimes there can occur different DTCs like clutch failure, invalid signal etc, but focus only on this one.

  • Picture of diagnostic before fixing:

Screenshot 20220528 101959 AlfaOBD

  • Picture of diagnostic after fixing:

Screenshot 20220531 160737 AlfaOBD

  • Compare video of old vs new electric motor work and sound:
  • Point by point diagnosis and fix:
  1. Check condition of battery, recharge it, eventually replace.
  2. Check Smart Driver Unit, it is main power module for TCT Gearbox, probably it should throw another DTC if there is some problem, but you can check in AlfaOBD "Electro pump pilot unit command % (duty cycle)", it should oscillate from 10% to 90%.

Smart Driver Unit

Smart Driver Unit Duty Cycles

3. Check relay and fuse in engine bay fuse box, in case of Giulietta it is:

  • TCT Pump - F83 - 40A fuse
  • TCT Pump - T30 - 50A relay

Fuses

4. Check voltage output connector to the electric motor, if TCU tries to wake-up it, it should be 12V.

Voltage at connector

If everything of above is alright, then you can unplug connector from electric motor and check for resistance, in bad motor I had from 0.2KOhm to 0.3KOhm, or you can just unscrew the electric motor and connect the connector, then switch on ignition, it should start automatically. If it's not then the starting switch is not working anymore.

In my case I could start the motor with hand help: connected the plug, then rotated shaft by hand and the motor started. Of course only for short moment.

5. Replace if you have case described as above, ONLY the electric motor, part number: MAGNETI MARELLI 023000037010 or 71769629.
6. Open AlfaOBD, do procedure of: electric unit replacement and clutch bleed and it should be ready to go.

  • Too add:
  1. Forgot about checking resistance of new electric motor.
  2. I will send the old to some good mechanic of stuff like that, to see if it's reparable.

If you have any questions, ask.