ECM/PCM Power Input Signal Low
The P2507 code indicates that the Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected a low voltage condition on its main power supply circuit. This typically occurs when the battery voltage drops below a specified threshold (often around 9-10 volts) while the ignition is on. The ECM/PCM relies on a stable power supply to operate sensors, actuators, and communication networks. Low voltage can result from a weak battery, poor electrical connections, a failing alternator, or excessive voltage drop in the power feed circuit. This code may also be triggered by a faulty ECM/PCM internal power supply regulator.
1. Most Common Causes
- Weak or discharged battery
- Alternator not charging sufficiently
- Battery terminals corroded or loose
- Corroded or damaged wiring in the ECM/PCM power circuit
- Harness connectors with excessive resistance due to corrosion or looseness
- Blown fuses or fuses with high resistance in the power circuit
- Faulty ignition relay with deteriorated contacts
- Poor ECM/PCM ground connection
- Internal ECM/PCM failure (rare but possible)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Engine may crank slowly or fail to start
- Intermittent stalling or rough idle
- Dimming headlights or electrical issues
- Reduced engine performance or limp mode
3. Step-by-Step Diagnosis
Step 1: Check battery voltage with a multimeter (should be 12.6V+ engine off, 13.5-14.5V engine running).
Step 2: Inspect battery terminals and ground connections for corrosion or looseness; clean and tighten as needed.
Step 3: Test alternator output; if low, replace alternator.
Step 4: Check for voltage drop between battery positive and ECM/PCM power input pin; repair wiring if drop exceeds 0.5V.
Step 5: If all else passes, suspect internal ECM/PCM failure; perform manufacturer-specific tests or replace module.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code, as low voltage can cause erratic engine behavior, stalling, or failure to start. Continued driving may also damage the ECM/PCM or other electronic components.
How much does it cost to fix?▼
The cost to fix P2507 typically ranges from $50 to $150 for simple repairs like cleaning terminals or replacing a battery. If the alternator or ECM/PCM needs replacement, costs can exceed $500.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.