P0562 Code: System Voltage Low
The engine computer sees too little supply voltage – usually a charging, battery or ground problem.
At a glance
Severity: Moderate
- Meaning
- System Voltage Low
- System
- ECU & Outputs · Powertrain
- Safe to drive?
- With caution
- Typical repair cost
- $0–$900
- DIY difficulty
- Easy
The ECM constantly measures the voltage arriving at its own power pins. With the engine running, a healthy charging system holds roughly 13.5–14.8 volts; P0562 sets when the ECM sees voltage below a manufacturer-specific threshold for a set time. Because the ECM measures at its own connector, the cause can be a weak alternator or battery, but just as often a loose battery terminal, a corroded ground strap or a high-resistance feed. Low voltage upsets many modules at once, so P0562 frequently shows up alongside communication codes and a dash full of warning lights.
Can I keep driving? Drive only as far as needed to get it tested. If the alternator is failing, the car can die in traffic once the battery is drained, and electric power steering may cut out – switch off heated seats, rear defrost and other big loads on the way.
How to read P0562
- P Powertrain
- 0 Generic (SAE)
- 5 Speed, idle & inputs
- 62 Specific fault
Symptoms
- Battery or charging warning light on
- Dim or flickering headlights, especially at idle
- Slow cranking or no start after the car sits
- ABS, traction or airbag lights coming on together
- Harsh shifting or transmission in fail-safe mode
- Radio, clock or gauges resetting or glitching
- Rough idle or stalling with electrical loads switched on
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Failing alternator or internal voltage regulator
- Weak or failing battery (bad cell, sulfated)
- Loose or corroded battery terminals or cable ends
- Corroded or broken engine-to-body ground strap
- Worn or slipping serpentine belt or weak tensioner
- Blown alternator fuse/fusible link or damaged charge wire
- Fault in the ECM power relay or supply circuit
Diagnosis step by step
Measure resting battery voltage
After the car has sat for at least an hour, a healthy, charged battery reads about 12.6 V. Below 12.4 V it is discharged – charge it fully before judging anything else.
Tools: Multimeter
Check charging voltage under load
Engine at about 2,000 rpm with headlights, blower and rear defrost on: you should see roughly 13.5–14.8 V at the battery. Voltage hovering at or below 12.5 V points to the alternator, belt or charging circuit.
Tools: Multimeter
Load-test battery and alternator
Many US auto parts stores test batteries and alternators for free. A battery with a shorted cell drags system voltage down even when the alternator is healthy.
Tools: Multimeter
Voltage-drop test cables and grounds
While cranking or with heavy loads on, measure between the battery negative post and the engine block, and between the battery positive post and the alternator output stud. More than about 0.3 V indicates a corroded cable, loose terminal or bad ground strap.
Tools: Multimeter, Screwdriver
Inspect the belt and alternator connections
Look for a glazed or cracked serpentine belt, a bouncing tensioner and a loose alternator plug. A squeal at startup or when the A/C kicks on suggests belt slip.
Tools: Flashlight
Compare battery and ECM voltage
Read the control module voltage PID on the scan tool and compare it with the battery reading. A difference of more than about half a volt means the fault lies in the ECM's feed or ground rather than in the charging system.
Tools: OBD-II scanner, Multimeter
Where the parts are
- 1Battery
- 2Alternator
- 3Engine computer (ECM)
- 4CAN bus
- 5Transmission
- 6Wheel speed sensor
- 7High-voltage battery
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Clean and tighten battery terminals | Yes | $0–$50 |
| Replace battery (flooded or AGM) | Yes | $150–$400 |
| Replace serpentine belt and tensioner | No | $100–$300 |
| Repair or replace ground strap or battery cable | No | $60–$250 |
| Replace alternator | No | $400–$900 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Notes by brand
BMW
BMWs with an intelligent battery sensor must have a new battery registered (and coded if the type or capacity changes). Skipping this leaves the charging strategy set for the old battery, which can lead to undercharging and repeat low-voltage faults.
Field data
| Dodge | 2 | Journey |
|---|
Source: NHTSA Complaints API (US government open data), analyzed by DTC mention.
Emissions / smog test impact
Depends
Not every vehicle turns on the check engine light for P0562, so results vary. If the light is on, the car fails an OBD emissions test; either way, fix the charging problem first, because clearing codes resets the readiness monitors.
Frequently asked questions
I put in a new battery – why is P0562 back?
A new battery only hides a charging problem until it runs down. If the alternator, belt, cables or grounds are at fault, system voltage drops again. Test charging voltage and do voltage-drop checks on the cables.
Is 12.8 volts with the engine running normal?
On older cars, no – expect roughly 13.5–14.8 V. Many newer vehicles use smart charging that deliberately lowers alternator output at times to save fuel, so a brief reading around 12.5–13 V can be normal there. A reading that stays low under heavy load is not.
Can low voltage damage my ECM?
Low voltage itself rarely damages modules, but it causes erratic behavior and false codes in many systems. Bigger risks are jump-starting with reversed cables or disconnecting the battery while the engine runs, which can create voltage spikes.
Why do I have so many other codes with P0562?
Modules need stable voltage to talk on the CAN network. When voltage sags, they drop off the network and store U-codes such as U0100 or U0121. Those usually disappear once the voltage problem is fixed and codes are cleared.