Jaguar XK Battery Issues Point to Faulty Voltage Sensor

Having experienced a similar situation with a 2006 XKR, I can share some relevant battery maintenance insights as someone with moderate experience in car repairs. Initially suspected a dying car battery, but after proper battery testing, the readings were normal just like in your case. The symptoms were identical, slow cranking, dim lights, and inconsistent electrical behavior. The workshop diagnosed a faulty battery sensor, which was incorrectly reporting the battery charge status to the vehicle management system. The repair involved replacing the battery sensor unit and recalibrating the charging system. Total cost was 315€, including diagnostics and labor. The fix resolved all electrical issues completely. Before proceeding with repairs, could you provide: Current battery age and maintenance history, Any error codes showing on the dashboard, Whether the charging system warning light comes on, If the battery health has been professionally tested recently This information would help determine if your issue matches my experience exactly. While battery sensor problems are common in these models, a thorough battery testing process is essential to rule out other potential causes. Would also suggest checking the alternator output voltage to ensure its not contributing to the charging system problems.

Thanks for the detailed response. Latest service was at 142737 KM and battery testing was performed last month. The car battery itself is actually only 8 months old. No warning lights on the dashboard, but I noticed the voltage gauge occasionally shows slightly lower readings than normal. Using a multimeter, I measured 14.2V while running and 12.4V when off, which seems within spec despite the symptoms. Called a local shop and they quoted 380€ for complete vehicle diagnostics and voltage sensor replacement if needed. Planning to bring it in next week, but wanted to verify if this price sounds reasonable based on your experience.

Thanks for the additional details. The voltage readings you shared actually match what I saw with my XKR before the repair, technically within spec but still experiencing issues. The battery charge indicators can be deceptive when the battery sensor is faulty. The 380€ quote sounds in line with what I paid (315€), considering prices have increased since my repair. The battery sensor replacement itself isnt expensive, but the labor and system recalibration make up most of the cost. The fact that your battery is only 8 months old further supports the likelihood of a sensor issue rather than a battery problem. When my battery sensor was failing, it caused the charging system to misread the battery charge levels, leading to similar symptoms despite having good voltage readings. One thing to note from my experience, make sure the shop performs a full charging system diagnostic before replacing parts. My mechanic found that the faulty battery sensor was causing the system to undercharge the battery intermittently, even though basic voltage testing showed normal readings. Also worth mentioning that after my repair, the voltage readings became more stable and the battery maintenance system started functioning correctly again. The slow cranking and lighting issues disappeared completely.

Really appreciate the insights about the charging system and voltage specifics. This matches my situation perfectly, especially the part about intermittent undercharging despite normal battery charge readings. Having a new battery that shows these symptoms definitely points toward the sensor issue you mentioned. Going to proceed with the shop appointment next week. The quoted 380€ seems reasonable given your repair costs and current prices. Will make sure they run complete diagnostics on the battery sensor and entire charging system before replacing any components. Will update once the repair is done, but feeling more confident now that the voltage sensor is likely the root cause, especially since all the symptoms align with your experience. Thanks for sharing the specific details about the repair process and resolution, exactly the kind of first-hand information I was looking for.