P2507 on 2014-2017 Mazda MAZDA6: PCM Power Input Low Causes and Fixes

What's Unique About the 2014-2017 Mazda MAZDA6

The Mazda6, like other Mazdas from this era (including the CX-5, Mazda3, and MX-5), has a specific procedural quirk that can trigger P2507. Mazda issued Technical Service Bulletins (TSBs) explaining that this code, often paired with P2610, will set if the engine is started three or more times after the 15A 'ROOM' fuse is removed. This fuse is sometimes pulled to prevent battery drain during shipping ('transport mode'), which is often indicated by "F0-002" on the odometer. Therefore, the first diagnostic question is always whether this fuse was recently handled, as this is a common cause that doesn't indicate a part failure.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light is on
• Engine may stall, sometimes intermittently while driving or at idle
• Possible no-start condition or slow, hesitant cranking
• i-stop system (if equipped) may be disabled or show a malfunction message
• Erratic behavior from other electrical components like dimming/flickering lights, infotainment system glitches, or slow power windows
• Other warning lights, such as for the DSC (Dynamic Stability Control) or TPMS, may illuminate

Most Likely Causes

1. 15A ROOM Fuse Was Recently Removed 🔴 High Probability As documented in Mazda TSBs #01-003-21-3776 and #01-003-19-3557, starting the engine 3 or more times with this fuse removed will intentionally log P2507 and P2610. This is a procedural artifact for transport/storage ('transport mode'), not a vehicle fault.
   How to confirm: Check if the 15A ROOM fuse in the under-hood fuse box was recently pulled and re-inserted. Ask if any recent service was performed. The odometer may have displayed 'F0-002' while the fuse was out.
   Typical fix: Ensure the fuse is properly seated, clear the diagnostic trouble codes with an OBD-II scanner, and cycle the ignition.
   Est. part cost: $0
2. Weak or Failing Battery 🟡 Medium Probability → Shop Vehicle Battery The original battery has a typical lifespan of 3-5 years. Constant power draw from modern electronics can expose a weak battery, causing its voltage to drop below the PCM's threshold, especially during cranking. Models with i-Stop require a specific EFB (Enhanced Flooded Battery) or AGM battery.
   How to confirm: Test the battery voltage with a multimeter. A healthy battery should read at least 12.4V with the engine off. A professional load test at an auto parts store is the most definitive test. Needing frequent jump-starts is a clear sign of a failing battery.
   Typical fix: Replace the battery. Ensure the correct type (standard, EFB, or AGM) is used.
   Est. part cost: $150-$350
3. Corroded or Loose Battery Terminals/Cables 🟡 Medium Probability → Shop Vehicle Battery Corrosion on the battery terminals or ground connections acts as a resistor, causing a voltage drop between the battery and the PCM. This is a common issue on any vehicle as it ages.
   How to confirm: Visually inspect the battery terminals, cable ends, and the main chassis ground point for white/blue/green crust (corrosion) or looseness. Ensure the clamps cannot be moved by hand.
   Typical fix: Disconnect the battery (negative terminal first), clean the terminals and cable clamps with a wire brush and baking soda solution, apply anti-corrosion grease, and re-tighten securely.
   Est. part cost: $1-$10
4. Failing Alternator ⚪ Low Probability → Shop Alternator
   How to confirm: With the engine running, test the voltage at the battery terminals. A healthy alternator should provide between 13.5V and 14.5V. If the voltage is low or fluctuates wildly, the alternator is likely failing.
   Typical fix: Replace the alternator.
   Est. part cost: $250-$500
5. Faulty PCM Power Relay (EGI Relay) ⚪ Low Probability
   How to confirm: Locate the main relay (often labeled 'MAIN' or similar in the fuse box diagram). You can swap it with an identical relay from a non-critical system (like the horn) to see if the problem resolves.
   Typical fix: Replace the relay. A common multi-use relay part number is G110-67-730.
   Est. part cost: $15-$40

Rare But Worth Checking

• Damaged Wiring or Poor Ground Connection: A corroded or broken wire in the harness between the battery, fuse box, and PCM can cause this code. A YouTube video for a Mazda 3 with P2507 showed a corroded wire under the fuse box was the culprit. Check the main ground strap from the battery to the chassis and the engine/transmission to the chassis for corrosion or damage.
• Faulty Powertrain Control Module (PCM): → Shop Engine Control Module (ECM) This is extremely rare and should only be considered after all other possibilities have been definitively ruled out. A forum user on Mazdaspeeds.org noted that in 10 years of managing shops, a PCM was the actual cause only a handful of times.

Diagnosis Steps

1. Ask the owner: Was the 15A ROOM fuse in the engine bay fuse box recently removed for any reason? If yes, reinstall it, clear the codes, and see if they return. This is the most common cause per Mazda TSBs.
2. Scan for other codes. Note if P2610 is present, as this strongly reinforces the ROOM fuse scenario.
3. Inspect Battery Terminals: Check for and clean any corrosion on the battery posts and cable clamps. Ensure they are tight and cannot be wiggled.
4. Test Battery Health: With the engine off, use a multimeter to check battery voltage. It should be above 12.4V. A professional load test is recommended to confirm the battery's ability to hold a charge under stress.
5. Test Charging System: Start the engine and measure the voltage at the battery. It should be between 13.5V and 14.5V. If not, the alternator may be faulty.
6. Inspect Fuses and Relays: Visually inspect the 15A ROOM fuse. Check the MAIN fuse and the PCM/EGI main relay in the under-hood fuse box. You can swap the relay with a known good one (e.g., horn relay) as a quick test.
7. Check for Voltage Drop: If the above steps are normal, perform a voltage drop test on the main ground connections (battery to chassis, chassis to engine block). A reading above 0.2V indicates a problem. For advanced diagnosis, check for voltage at the PCM power input pins. A forum post for a similar model identified power pins as 1BA (Red) and 1BE (Green/Orange).
8. Final Check: Only after confirming all wiring, grounds, and power sources are good should a faulty PCM be considered.

Parts You'll Likely Need

• Battery (OEM #PE1T-18-520-9U (Example for non i-ELOOP models)) — The most common 'real' failure causing this code is an old battery that can no longer provide stable voltage to the PCM. Models with i-Stop/i-ELOOP require a more robust EFB or AGM battery.
  Trusted brands: Deka, Interstate, DieHard, Duralast
  OEM price range: $200-$350
  Aftermarket price range: $150-$300
• Battery Terminal Clamps — If the original terminals are too corroded to be cleaned effectively, they must be replaced to ensure a solid connection.
  Trusted brands: Dorman, Standard Motor Products
  OEM price range: $20-$50
  Aftermarket price range: $10-$25
• PCM Power Relay (EGI/Main Relay) (OEM #G110-67-730 (Multi-use relay)) — This relay supplies the main power to the PCM. A failing relay can cause an intermittent voltage drop. This is a common relay used for multiple functions in the vehicle.
  Trusted brands: Mazda (OEM), Denso, Bosch
  OEM price range: $30-$40
  Aftermarket price range: $15-$30

Related Codes That Often Appear With This One

• P2610 — P2610 (Instrument cluster internal engine off timer performance problem) is frequently stored with P2507. According to Mazda TSBs #01-003-21-3776 and #01-003-19-3557, their appearance together is a strong indicator of the 'ROOM fuse' scenario.

Technical Service Bulletins (TSBs) & Recalls

• 01-003-21-3776: The most recent TSB, covering up to 2021 models, which notes that P2507 and P2610 may be stored after engine start if the 15A ROOM fuse was removed.
• 01-003-19-3557: An earlier version of the same bulletin, documenting the same ROOM fuse condition for setting P2507 and P2610 across many Mazda models.
• 01-018/15: A superseded TSB from 2015 that also describes the P2507/P2610 issue related to the ROOM fuse, confirming this has been a known condition for a long time.

Platform-Specific Known Issues

• A known condition documented in TSBs #01-003-21-3776 and #01-003-19-3557 where starting the engine with the 15A ROOM fuse removed will cause P2507 and P2610 to be stored. This is not a malfunction but a result of a specific service procedure.
• The odometer will display 'F0-002' when the vehicle is in this 'transport mode' with the ROOM fuse removed.

Mechanic-Grade Diagnostic Values

• PCM Keep-Alive (Backup) Voltage — expected: Above 6V. Failure: Voltage drops below 6V for 5 seconds or more, triggering P2507.
• Scan Tool PID 'VPWR' (Vehicle Power) — expected: Should read B+ (Battery Voltage). Failure: A reading significantly lower than battery voltage at the terminals indicates a voltage drop in the supply circuit.
• Ground Circuit Resistance — expected: < 0.1 Ω. Failure: Resistance higher than 0.1 Ω between a ground point (like G-02 or G-03) and the negative battery terminal indicates a poor ground connection.
• Alternator Charging Voltage — expected: 13.5V - 14.5V with engine running. Failure: Voltage below 13.5V or above 14.5V indicates a charging system fault.

Scan Tool Commands That Help

• Mazda M-MDS or FORScan: Read PID Data (e.g., 'VPWR') — To monitor the voltage the PCM is reporting in real-time, which helps confirm if the low voltage condition is present at the module itself.
• Mazda M-MDS or equivalent: Clear DTCs — This is a required step after addressing the 'ROOM fuse' scenario as described in Mazda TSBs.
• No Tool Required: KAM (Keep Alive Memory) Reset — After replacing the battery or fixing a power supply issue, a KAM reset can clear adaptive learning tables. One method is to disconnect the battery cables and hold them together for 30 minutes. Another is to rapidly depress the brake pedal 20 times with the key on, confirmed by the oil pressure gauge sweeping.

Wiring & Ground Locations

• PCM Connector Pin 2O — At the main PCM electrical connector in the engine bay.. This is the specific terminal that receives backup power from the battery via the MAIN 200A and ENG+B 7.5A fuses. The PCM monitors voltage at this pin to set code P2507.
• G-02 / G-03 (Ground Points) — G-02 is typically located on the left (driver's side) front of the engine compartment. G-03 is on the left side of the engine compartment.. These are primary chassis ground points in the engine bay. A loose or corroded connection at these points can create a poor ground reference for the PCM, leading to incorrect voltage readings and triggering P2507.
• PCM Connector Pins (Power/Ground) — At the main PCM electrical connector.. For advanced testing, specific pins can be checked. On a similar Mazda platform, power inputs were identified as 1BA (Red) and 1BE (Green/Orange), with grounds at 1AZ, 1BH, 1BD, 1BG, and 1BB (all Black). These provide direct test points for voltage drop tests.

Real Owner Repair Stories

• Reddit user @Interesting-Lunch902 (2018 Mazda CX-3 (shares Skyactiv platform and electrical architecture)) — Check engine light was on/off intermittently with code P2610. Eventually, the car would not start, though dash lights and headlights worked. Required a jump start.
  ❌ Tried (didn't work) Having the battery 'checked' (user was skeptical of the result since lights worked)
  ✅ What actually fixed it Replacing the 5-year-old original battery resolved the starting issue and the trouble code.