Weak or failing battery that cannot hold a stable charge under load; Corroded, loose, or damaged battery terminal connections; Faulty or worn alternator not maintaining proper charging voltage; Blown or corroded main fuse or fusible link in the under-hood fuse box; Damaged power wire or ground strap between the battery, chassis, and PCM; Poor ground connection at the PCM or engine block; Internal PCM power supply fault, though this is the least common cause

DTC codes / Mazda codes / P1562

P1562 · MazdaPowertrain Control Module +B Voltage Low

Q: What does code P1562 mean?

Powertrain Control Module +B Voltage Low. P1562 on Mazda vehicles means the Powertrain Control Module (PCM) has detected that its main power supply voltage, the +B circuit, has dropped below the normal operating threshold. The PCM monitors this feed continuously and stores the code when the voltage falls low enough to risk unstable operation or memory loss.

P1562 on Mazda vehicles means the Powertrain Control Module (PCM) has detected that its main power supply voltage, the +B circuit, has dropped below the normal operating threshold. The PCM monitors this feed continuously and stores the code when the voltage falls low enough to risk unstable operation or memory loss.

SystemPowertrain

Code typeMazda specific

SeverityMedium

Fix difficultyIntermediate

AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

Illuminated Check Engine Light, often with no other noticeable symptoms
Intermittent rough running or stalling, especially at idle or during electrical load
Slow or failed engine start, sometimes with a clicking sound from the starter area
Erratic transmission shifting or harsh engagement on automatic models
Accessory electrical glitches such as dimming lights or radio resets
Multiple unrelated trouble codes stored in memory due to low voltage

Common causes, most likely first

Weak or failing battery that cannot hold a stable charge under load
Corroded, loose, or damaged battery terminal connections
Faulty or worn alternator not maintaining proper charging voltage
Blown or corroded main fuse or fusible link in the under-hood fuse box
Damaged power wire or ground strap between the battery, chassis, and PCM
Poor ground connection at the PCM or engine block
Internal PCM power supply fault, though this is the least common cause

How to diagnose and fix it

Perform a battery load test and check static voltage with a multimeter; replace the battery if it fails
Inspect and clean battery terminals, clamps, and the battery-to-chassis ground strap
Check charging voltage at the battery with the engine running; repair or replace the alternator if output is low
Inspect the main fuse box for blown fuses or fusible links related to the PCM +B circuit
Back-probe the PCM power connector to verify voltage at the module under load
Check and clean the PCM ground connections on the engine block and chassis
Clear the code and test-drive to confirm the fault does not return; replace the PCM only after all wiring checks pass

Low voltage codes often misdiagnosed as PCM failure

A battery that passes a simple voltage check can still fail a proper load test, so always load-test before condemning the PCM.
Corrosion hidden inside a battery cable under the insulation can cause voltage drops that only appear under electrical load.
This code frequently appears alongside multiple unrelated codes because low voltage disrupts several modules at once, so fix the power supply before chasing other codes.
Aftermarket accessories wired directly to the battery or PCM circuit can introduce parasitic draws that trigger P1562 overnight.
A loose alternator belt or failing voltage regulator can cause intermittent low voltage that only sets the code during certain driving conditions.

Can I keep driving with P1562?

You can usually drive a short distance to a repair shop, but avoid long trips or heavy electrical loads such as rear defroster and high beams. If the engine stalls or electrical systems behave erratically, pull over safely and arrange a tow.

Tools that help

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Guidance is general and written for Mazda vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.