P2505
ECM/PCM Power Input Signal
- Severity
- High
- Driving
- Drive only to a garage
A fault in the engine control module's power input signal. The module monitors its own supply, and this is that check failing. Modules need a stable voltage to drive actuators accurately, so a supply problem shows as poor running long before the module actually stops working.
Possible causes
- CommonWeak or failing battery
- CommonCorroded earth strap or module earth point
- CommonCorroded or loose battery terminals
- CommonCharging system fault - a failing alternator or regulator
- PossibleBlown fuse or failing relay in the module supply
- PossibleDamaged supply wiring
What you might notice
- Erratic running or stalling
- Limp mode
- Several unrelated warning lights
- Slow cranking
- Module resetting while driving
- Check engine light on
What to check, in order
- Check battery voltage, the terminals and the earth straps first. An unstable supply produces faults across unrelated systems, and chasing those individually wastes a great deal of time.
- Measure battery voltage with the engine off and again running, and compare both against specification.
- Perform a voltage drop test on the module's supply and earth. High resistance in a corroded connection produces exactly this with nothing looking wrong.
- Check the charging system output under load - lights and heated screen on.
- Do not order a control module on the strength of a power supply code. The module is reporting a problem, not necessarily having one.
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