P0517
PowertrainBattery Temperature Sensor Circuit High
The battery temperature sensor tells the charging system how warm or cold the battery is, so the ECM can adjust the charging voltage accordingly. A cold battery wants a bit more voltage, a hot one wants less. When the ECM sees an unusually high voltage from that sensor circuit, it sets P0517 and assumes the reading is bogus. This is almost always a wiring or sensor fault rather than a battery that's actually cooking itself.
ⓘ Information only. This page provides general educational information about fault code P0517. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does P0517 mean?
P0517 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Battery Temperature Sensor Circuit High.
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • Engine warning light on, frequently the only thing you'll notice
- • Battery not charging properly when it's cold out, so it feels flat on frosty mornings
- • Slightly down on fuel economy on some cars as the charging strategy drops to a safe default
- • Harder cold starts in winter if the battery isn't getting topped up correctly
- • Battery management running in default mode, ignoring the missing temperature data
- • Plenty of cars show no drivability problems at all, just the dash light
Possible causes
Causes commonly associated with P0517, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Broken or open wiring in the sensor harness, the most common cause, often where the loom runs near the battery tray and chafes through
- 2. Corroded or loose connector terminals at the sensor or the ECM, salt and damp from winter roads love to attack these
- 3. The battery temperature sensor itself gone faulty and reporting nonsense
- 4. Short to voltage somewhere in the sensor circuit pulling the reading high
- 5. Damaged battery cable or harness near the sensor, sometimes from previous battery work done in a hurry
- 6. Failed ECM, but this is rare and you check everything else first before you go anywhere near it
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Scan the car and confirm P0517 is actually stored, then note any other codes sat alongside it, charging faults like P0562 often turn up together and point you at the same area
- 2. Get your eyes on the sensor connector and the wiring around the battery. Look for green corrosion, chafed insulation, and pins that have backed out of the plug
- 3. Measure the sensor's resistance with a multimeter and check it against the manufacturer's figures for the temperature it's sitting at, a sensor reading open or wildly off needs replacing
- 4. Check the circuit wiring for continuity and that it's getting its proper reference voltage, this catches the broken wire that a quick visual misses
- 5. Watch the live sensor data on the scanner. If the reading is pinned at maximum or jumping around when nothing's changing, that confirms the circuit fault
- 6. Only if the sensor and every bit of wiring check out should you start considering the ECM, and that's a last resort
Common questions about P0517
Is a cheap pattern sensor fine or should I buy genuine? +
For the sensor itself a decent quality aftermarket part is fine on most cars, you're talking £15-£40 and the cheaper ones do the same job. The thing to avoid is the bargain-bin no-name temperature sensors that read inaccurately out of the box, because then you'll be chasing the same code again. Stick to a known brand. And before you spend anything, make sure the sensor is the actual fault, because a corroded connector or a chafed wire is by far the more common culprit and a new sensor won't fix that.
Can I keep driving with P0517 showing? +
Short term, yes, the car will run and drive normally. What you lose is the smart charging adjustment, so in cold weather the battery may not get charged as well as it should, which can leave you with sluggish starts and a flat battery over a hard winter. It's not an emergency, but don't ignore it for months either. Sort it before the cold sets in and you'll save yourself a no-start on a freezing morning.
Will this stop me passing the MOT? +
The code on its own isn't a fail. What can catch you out is the engine warning light being lit when the tester looks at the dash, an illuminated MIL can lead to a fail. If you've fixed the underlying wiring or sensor, drive it a few cycles to let the light clear before you book it in. The battery temperature sensor isn't part of the emissions tailpipe test, so the only risk here is that warning lamp being on at the time of inspection.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →