OBD-II Diagnostic Trouble Code
P0562 — System Voltage Low
P0562 means the ECM measured supply voltage below its minimum threshold for a set time while the engine was running. The battery is not being charged properly or there is excessive resistance in the power feed to the ECM.
Severity 4/5
Truck-relevant
Stop within 50 mi
Severity
Stop within 50 mi
System Voltage Low
Code
P0562
Category
Powertrain
Subsystem
Network
Truck-relevant
Yes
What this means for truckers
P0562 (System Voltage Low) — charging system isn't keeping up. Tests: (1) battery voltage with engine off — should be 12.6V minimum (12V) / 25.2V (24V). (2) Voltage with engine running — should be 13.8-14.4V (12V) / 26-28V (24V). If running voltage equals static, alternator is bad. If running voltage is way under, regulator or wiring.
Before you replace parts — try this first
P0562 on the Network system is most often failing alternator or regulator — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Charge or battery warning light, dim lights, slow cranking, no-start after sitting, and possibly other module communication codes. Some electronic functions may shut down to conserve power.
Common causes
- CommonFailing alternator or regulator ($400–$1200)
- CommonWeak or sulfated batteries ($200–$900)
- CommonCorroded cables or loose ground connections ($50–$300)
- OccasionalSlipping or broken alternator belt ($80–$250)
- OccasionalElectrical load exceeding alternator output (inverters, added lighting) or high parasitic draw ($100–$400)
How to fix
Check charging voltage at the batteries with engine running (typically 13.5-14.5V on 12V systems)
When to use: First step
Load test each battery individually
When to use: When charging voltage is acceptable
Voltage drop test the positive and ground circuits
When to use: When batteries and alternator test good
Replace alternator, batteries or cables as indicated
When to use: Based on test results
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → P0500 — Vehicle Speed Sensor Malfunction
- → P0501 — Vehicle Speed Sensor Range/Performance
- → P0502 — Vehicle Speed Sensor Low Input
- → P0503 — Vehicle Speed Sensor Intermittent/Erratic/High
- → P0506 — Idle Control System RPM Lower Than Expected
Frequently Asked Questions
Can I drive with code P0562?
Drive with caution. P0562 is severity 4 — stop within ~50 miles. Most commercial diesel codes at this severity (turbo, fuel rail, transmission solenoid) can damage adjacent expensive components if left unrepaired. Get to a service location before highway-speed loads.
How much does it cost to fix P0562 on a commercial truck?
Total repair cost ranges $50–$1200 depending on the root cause. The cheapest fix is usually the first one listed below — Failing alternator or regulator — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will P0562 fail a DOT inspection?
P0562 is generally not a direct DOT inspection fail item by itself. Inspectors focus on safety-critical systems (brakes, steering, tires, lights, hours-of-service). However, the check engine light alone can trigger additional inspection scrutiny. Best practice: fix the code and clear it before a planned inspection.
What's the difference between P0562 and related codes?
P0562 is closely related to: P0500 (Vehicle Speed Sensor Malfunction), P0501 (Vehicle Speed Sensor Range/Performance), P0502 (Vehicle Speed Sensor Low Input), P0503 (Vehicle Speed Sensor Intermittent/Erratic/High). These codes share the same subsystem (network) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only P0562 is set without the companions, the issue is more isolated.
How do I prevent P0562 from coming back after a repair?
For P0562 (System Voltage Low), prevention centers on the network system. Pay attention to ground connections at every PM — bad grounds are 70% of communication codes. Inspect harness routing for chafe points. Don't disconnect modules with the key on.