P0034, P261C and EPC Light - Going in circles

[Hazlow]

Hi all,

Looking for some advice on a 2018 SEAT Ateca 1.4 TSI EA211 that has developed ongoing EPC/start-stop faults after a coolant wiring contamination issue.

It started with:

• EPC light
• Limp mode
• Start/stop error
• Reduced power

Original codes included:

• P261C
• P0034
• P0641
• P0237
• P2562
• P0122/P0222/P2122 etc.

I eventually found coolant contamination/corrosion in connectors around the turbo area. A mechanic later diagnosed a leaking coolant temperature sensor that had wicked coolant through the wiring loom.

So far I have:

• Replaced the leaking coolant temp sensor
• Replaced the auxiliary coolant pump
• Cleaned ECU connector thoroughly
• Cleaned affected connectors with contact cleaner
• Inspected loom for obvious corrosion/damage
• Checked MAP, throttle body, turbo actuator, oil pressure valve connectors
• Battery and grounds seem OK

The car now drives mostly normally, although still restricts power a bit and:

• EPC light and start/stop error still return
• Codes currently are mainly:
  • P261C
  • P0034
• Codes usually return after restarting the engine
• Cleaning/reseating ECU connector temporarily improves things

One ECU pin was also found slightly bent outward at one point, so I’m wondering if a female ECU terminal may now have poor contact tension.

Before I go down the route of loom or ECU replacement:

• Has anyone seen coolant wick all the way into the ECU connector on an EA211?
• Did cleaning/repairing terminals solve it?
• Has anyone had ECU driver damage from this?
• Any known shared circuits/grounds between P261C and P0034?

Trying to avoid replacing the entire loom/ECU unnecessarily.

Thanks!

 

[James_R]

Trying to avoid replacing the entire loom/ECU unnecessarily.

That's going to be the only reliable resolution here.