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.
Air Conditioning (ECC And MCC Only)
The engine control module (ECM) controls the A/C compressor. When the A/C switch on the dashboard environment panel is activated, a request to activate the compressor is transmitted via Control area network (CAN) to the engine control module (ECM). The engine control module (ECM) determines when the compressor must operate.
If any of the following conditions are met the compressor is disconnected:
- High engine coolant temperature (ECT)
- Wide open throttle (WOT)
- The engine has just been started
- Overpressure in the air conditioning (A/C) system.
When the engine is started the engine control module (ECM) activates the air conditioning compressor for a short period even if the climate control module (CCM) has not transmitted a request about this. This is carried out for diagnosis. This check is carried out at all temperatures exceeding -6 °C.
The advantage in allowing the engine control module (ECM) to control the air conditioning compressor is that it can delay compressor activation somewhat, if the idling speed must be compensated for the extra load for example.
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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.
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