Mercedes-Benz: Coolant light on in instrument cluster and coolant pump over speed fault in PTCU

Models affected:

Mercedes-Benz - all models with electric cooling pumps

Issue / Symptoms:

Yellow coolant warning on Instrument cluster and possible fault in the PTCU (power train module) “The rpm of component 'Coolant pump' is too high” following the coolant system being opened.

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Warning Light on IPC

Cause:

The fault can be caused by air in the coolant system allowing the pump(s) to run dry and over speed.

Repair Guidance:

The coolant system must be drained, filled and bled as per WIS instructions (group 20) using all the required tools.

Do not replace the pump, they have a “dry run detection” that turns them off to prevent damage.

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