P2502
Charging System Voltage
- Severity
- High
- Driving
- Drivable — book it in
There is a problem with the voltage the charging system is producing, without the module committing to whether it is too high or too low. Every electronic system on the vehicle depends on a stable supply, so a fault here tends to produce a scatter of unrelated codes elsewhere - modules misbehaving because of their power, not because anything is wrong with them.
Possible causes
- CommonWeak or failing battery
- CommonFailing alternator or voltage regulator
- CommonCorroded or loose battery terminals
- CommonCorroded earth strap between engine, body and battery
- PossibleSlipping or worn drive belt
- PossibleDamaged charging cable between alternator and battery
- PossibleHeavy aftermarket electrical load
What you might notice
- Battery or charging warning light
- Lights dimming, flickering or unusually bright
- Several unrelated warning lights and codes at once
- Slow cranking
- Electrical items behaving oddly
What to check, in order
- Measure battery voltage with the engine off and again with it running. Roughly 12.4 to 12.7 volts at rest and a steady charging voltage running is what you are looking for; anything well outside that has found the fault.
- Fix this before diagnosing anything else the car is doing. A supply problem sets codes across unrelated systems, and chasing those individually wastes a great deal of time.
- Clean and tighten the battery terminals and every earth strap you can reach. Corroded earths cause voltage problems that look exactly like failed components.
- Perform a voltage drop test on the main charging cable and the earth path.
- Check the drive belt tension and condition.
- Have the battery load tested rather than judging it on voltage alone.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx
Vehicle speed control, idle control and auxiliary inputs
P2500P2501P2502P2503P2504P2505P2506P2507P2508P2509P2510P2511P2512P2513P2514P2515P2516P2517P2518P2519P2520P2521P2522P2523P2524P2525P2526P2527P2528P2529P2530P2531P2532P2533P2534P2535P2536P2537P2538P2539P2540P2541P2542P2543P2544P2545P2546P2547P2548P2549P2550P2551P2552P2553P2554P2555P2556P2557P2558P2559P2560P2561P2562P2563P2564P2565P2566P2567P2568P2569P2570P2571P2572P2573P2574P2575P2576P2577