System voltage low on Mercedes — alternator failure and dual-battery system issues on S/E/GL with second battery.
Mercedes-Benz P0562 — System voltage low on Mercedes — alternator failure and dual-battery system issues on S/E/GL with second battery. Typical UK independent garage cost: £180–£720.
What actually causes P0562 on a Mercedes-Benz
Many modern Mercedes (S, E, GL, ML) run a dual-battery system — main starter battery plus a small auxiliary battery in the boot/wheel arch. The auxiliary battery fails first (around 4–6 years) and triggers P0562 even when the main starter battery is fine. On Sprinters the alternator brushes wear out around 120k miles. On C/E-Class W204/W212 a corroded battery sensor on the negative terminal causes phantom P0562.
Mercedes-Benz engines that log P0562
- C-Class W204/W205 (C220 CDI, C200 CGI)
- E-Class W212/W213 (E220 CDI, E250 CGI)
- Sprinter (411/411 CDI/313 CDI)
- ML/GL W164/X166 (ML350, GL350)
How we diagnose P0562 on a Mercedes-Benz
- Xentry / Star — read main and aux battery voltages
- Inspect battery sensor on main battery negative terminal
- Test both batteries separately under load
- Inspect alternator output and brushes (Sprinter especially)
- Code/register new battery via Xentry
The common misdiagnosis to avoid
Always check for an auxiliary battery on E/S/GL before fitting a main battery — fitting one and missing the failed aux battery means P0562 returns in days and customer's furious.
Mercedes-Benz P0562 repair cost in the UK
Expect £180–£720 including parts and labour at an independent garage. Main-dealer quotes on Mercedes-Benz are usually higher for the same job, and the spread exists because the cheap cause and the expensive cause throw the same code — pay for the diagnosis before you pay for parts.
Bob's workshop tip
On Sprinter 313/315 CDI vans showing P0562 with high mileage, consider going straight to a remanufactured alternator with new brushes (£280–£350 fitted) — it's the fastest path to a fix and brush wear is the cause 80% of the time at 120k+.
Codes usually seen alongside P0562 on Mercedes-Benz
- P0563
- P0620
- P0625
Symptoms drivers report with P0562
- Battery warning light flickers intermittently, especially at idle with electrical load on
- Dashboard dims when indicators are on or wipers run
- Car fails to start cold after sitting for 2–3 days
- Stop-start system disables itself with a 'battery saver active' message
- Voltmeter reads below 13.2V with engine running
Repairs that clear P0562
- Load-test battery
- Alternator output test
- Clean and torque earths
For the generic, all-makes explanation of this code — meaning, every known cause and UK cost bands — see our P0562 guide.
Reading P0562 on a Mercedes-Benz properly
A generic reader will show P0562 and nothing else. What matters is the freeze-frame data stored with it — engine speed, load, coolant temperature and fuel trims at the moment the fault was logged — plus whether any other module on the Mercedes-Benz has logged something at the same time. Codes rarely arrive alone, and the order they were stored in usually points at which one is the cause and which are the consequences.
Clearing P0562 without fixing it
Erasing the code resets the Mercedes-Benz's readiness monitors as well as the light. The fault returns on the next drive cycle if the cause is still there, and in the meantime the incomplete monitors can stop the car passing an emissions check. After a genuine repair, the car is driven until the relevant monitor completes before it is handed back.
Bob's Mechanical Repairs is an independent garage in Birnam, Dunkeld, Perthshire, with 32 years of Bob's experience on the tools. If P0562 is showing on your Mercedes-Benz, bring any scan results with you — we will read the live data ourselves, confirm which cause it actually is, and price the repair before any work starts.