Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Engine Temperature Control Module - GX33-, Checking: General Description
The Engine Temperature Control Module -GX33- combines several elements (thermostat, valves, coolant pump, etc.) into one component. Two mechanically connected rotary coolant valves (RCVs) are part of the module. The position of RCV 1 controls the coolant flow through the engine oil cooler, the cylinder head, and the main radiator. The RCV 2 controls the coolant flow through the cylinder block. The engine temperature can be adjusted to an optimum value regarding engine speed and load. In addition, the engine heat-up to optimum operating temperature is accelerated by the fact that the coolant circulation can be minimized. A position sensor detects the position of RCV 1. The monitor detects a stuck RCV. An emergency thermostat opens the main cooling circuit if the engine temperature is too high.
The Engine Temperature Control Module -GX33- contains the following components:
- Engine Temperature Control Actuator -N493-.
The Engine Temperature Control Module -GX33- components cannot be serviced separately, and they must be serviced as a unit.
Special tools and workshop equipment required
- Multimeter.
- Wiring Diagram.
- Scan Tool.
Test requirements
- Fuses OK.
- Battery voltage OK.
- Switch OFF all electrical and electronic accessories.
- Vehicles with automatic transmission, ensure the selector lever position is in "P".
- Vehicles with manual transmission, ensure the shifter lever position is in "N" with the parking brake applied.
- Observe all safety precautions: SAFETY PRECAUTIONS .
- View clean working conditions: CLEAN WORKING CONDITIONS .
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.