Controlled thermostat control-Short circuit to earth P0598

[darko]

Hi everyone,

Looking for some insight on an issue after replacing the thermostat housing on a 1.6 THP.

Immediately after the install, the ECU threw fault code P0598 - Controlled thermostat control - Short circuit to earth.

Here is what I’ve done and checked so far:

• Driving Condition: Car drives completely fine, holding normal operating coolant temps (around 90∘C–100∘C). No overheating, no limp mode.
• Tested Old Part: Reconnected the old thermostat plug to test, but P0598 remains active.
• Power Supply / Fuses: Main fuses (F10/PSF1) are intact, power is present on the 12V feed, and there are no other sensor/actuator fault codes logged.

Since putting the old thermostat back on didn't change anything, it seems the issue occurred during the swap (coolant in connector, pinched control wire, or ECU driver issue).

Before I start stripping down the wire loom back to the ECU:

1. Has anyone experienced coolant dripping into the 2-pin connector causing a persistent short reading even after drying?
2. Are there any known common chafing points on the THP thermostat harness branch near the intake/gearbox bracket?
3. If the control wire shorted to ground during installation, is it common for the ECU low-side driver transistor to latch/fuse closed on these Bosch MED17.4 units?

Appreciate any advice or pinout diagnostic steps!

 

[Pedro]

Very strange when you bought the replacement did it come with new connection tails ?