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2018 S60 T5 Start/Stop Not Working - Battery or Sensor?

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Mike T. · rep 0 · May 25, 3:55 AM · 1 replies · solved · Question

Vehicle: 2018 Volvo S60 T5

My 2018 Volvo S60 T5 has been acting strange lately. The automatic start/stop feature, which usually works fine, has completely stopped engaging. I've noticed it regardless of outside temperature or driving conditions.

I thought it might be the auxiliary battery, but I'm not getting any error messages on the dash. Could it be a sensor related to battery health or perhaps something else entirely? The main battery seems okay, no slow cranks. Any ideas?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:55 AM

0

ClearTheCode admin answer:

  1. Check Battery Health: The most common reason for the start/stop system to stop working is a weak main or auxiliary battery. Even without error messages, the battery management system (BMS) might disable start/stop if the battery charge or health is below a certain threshold to ensure reliable engine starting. Have your main 12V battery and, if applicable, the smaller auxiliary battery (often found in the trunk or under the hood) tested professionally for charge and cold cranking amps (CCA).
  2. Driving Conditions & System Requirements: The start/stop system has numerous conditions that must be met to engage, including:
    • Engine at operating temperature.
    • Ambient temperature within a specific range.
    • Battery charge level and health sufficient.
    • HVAC system not demanding maximum cooling/heating.
    • Steering wheel not turned sharply.
    • Brake pedal pressed sufficiently.
    • Vehicle speed reached a certain threshold since last start.
    • No active diagnostic trouble codes (DTCs).
  3. Diagnostic Scan: A professional diagnostic scan using a Volvo-specific tool (like VIDA) can reveal any hidden or pending codes related to the battery management system, engine control module (ECM), or other relevant modules that might be preventing the start/stop function. Common codes might not appear on the dash but could be stored internally.
  4. Software Update: In some cases, a software update for the vehicle's control modules can resolve unexpected electrical behaviors or improve battery management logic.
  5. When to See a Shop: If a simple battery check doesn't identify the issue, or if you don't have access to a diagnostic scanner, it's best to visit a Volvo dealership or an independent specialist. They can perform comprehensive battery tests, check for specific sensor failures (e.g., battery current sensor), and ensure all control modules are communicating correctly. Ignoring persistent electrical issues can sometimes lead to more significant problems down the line.
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