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.
Diagnostic Trouble Code (DTC) Information PHM-0020
Condition
The diagnostic trouble code (DTC) is stored if the phone module (PHM) registers an open-circuit or a short-circuit to +12 V in the microphone signal to the handset.
The diagnostic trouble code (DTC) can be diagnosed when the ignition is switched on (not key position 3) and when the battery voltage is 9-16 V.
Substitute Value
- Only hands-free operates.
Possible Source
- Short-circuit to +12 V in the cable (microphone signal) between the handset and the control module
- Open-circuit in the cable (microphone signal) between the handset and the control module
- Contact resistance, oxidation or loose connections in the connectors.
Fault symptom[s]
- The carphone handset is not working.
- Message in the text display (applies only to phone modules (PHM) with Volvo On Call).
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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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