ECM/PCM Power Input Signal Intermittent
The P2506 code means the vehicle's onboard diagnostic system has detected: ECM/PCM Power Input Signal Intermittent. This is a critical severity code.
- Keep driving?
- No -- stop driving
- DIY difficulty
- hard
- Estimated cost
- $150 - $1200 (parts and labor)
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Common Symptoms
- Random engine stalling
- Multiple dashboard warning lights
- Engine cranks but won't start intermittently
- Loss of scan tool communication
Probable Causes (Ranked by Likelihood)
- Corroded ECM power supply connector Very High
- Damaged wiring in ECM power circuit High
- Failing ECM main relay Moderate
- Loose battery cable causing voltage drops Moderate
Step-by-Step Diagnostic Procedure
-
Check ECM power supply voltage during cranking
-
Inspect ECM main relay and power distribution fuses
-
Test voltage drop across battery cables under load
-
Wiggle test ECM harness connector while monitoring signal
Common Fixes by Vehicle
What techs usually find when diagnosing P2506 on specific vehicles — tap your vehicle for the fix and the exact part:
2008-2016 Ford F-150/Escape/Focus easy DIY
P2506 = battery voltage saw an unexpected disconnect or dip. Most common cause: loose battery terminal or corroded ground cable. Remove both cables, clean with wire brush + baking soda, re-torque to 5 ft-lb, and apply terminal protectant.
Labor: 20 min2010-2018 Ford Fusion/Escape 2.0L/2.5L moderate DIY
Failed alternator causing voltage to drop below 11V under load. Load-test with a carbon-pile tester -- should hold 13.6-14.4V at 30A load. If it sags, replace alternator (Motorcraft or ACDelco OE). Aftermarket low-cost alternators often fail P2506 quickly.
Labor: 1-2 hours2008-2017 VW Passat/Audi A4/Q5 easy with VCDS DIY
VW/Audi BEM (battery energy management) module fault. After battery replacement the new battery MUST be coded to the car via VCDS/ODIS with the correct capacity and chemistry. Without coding, P2506 is inevitable within a few weeks.
Labor: 10 min codingFrequently Asked Questions
Why does my car randomly stall with P2506?
The ECM is losing power intermittently. Even a brief power loss stops fuel injection and ignition control, causing an immediate stall.
Can a bad battery connection cause P2506?
Yes. Loose or corroded battery terminals can cause voltage fluctuations that trigger this code.
Is P2506 an ECM failure?
Usually not. It more commonly points to wiring, connector, or relay issues. Internal ECM failure should be considered last.
Sources
This page is built from documented references. Verify against your own service info before repair work.
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