P0560 – System Voltage

P0560 is an OBD-II trouble code that points to a problem with the system voltage that your engine computer (ECU/PCM) is seeing. In plain language, the car’s brain is not happy with the voltage coming from the battery/charging system. This can be something simple like a weak battery or loose connection, or it can involve the alternator or wiring. If you caught this code on your scanner, you’re already ahead of the game. Let’s walk through what it means, common causes, symptoms, and how you can fix it.

What Does P0560 Mean?

P0560 stands for “System Voltage Malfunction.” Your vehicle’s powertrain control module (PCM) constantly monitors battery and charging system voltage. When the voltage is too low, too high, or unstable for a set period of time, it stores P0560 and usually turns on the check engine light.

This code doesn’t point to one single part. Instead, it tells you the PCM is seeing a voltage problem somewhere in the primary power or charging circuit. That includes the battery, alternator, main power cables, grounds, and sometimes the ignition switch or internal PCM power supply.

Quick Reference

  • Code: P0560 – System Voltage Malfunction
  • Severity: Moderate to serious, can lead to stalling or no-start
  • Most common causes: Weak battery, failing alternator, poor connections
  • Typical symptoms: Battery light, dim lights, hard starting, stalling
  • Risk: Can leave you stranded if ignored

Real-World Example / Field Notes

In the shop, I see P0560 most often on vehicles that come in with an intermittent battery light or random stalling at idle. One example: a mid-2000s sedan came in with P0560 and a complaint of dim headlights and rough idle at stoplights. Battery tested borderline but “okay” on a quick parts-store test. When I checked with a proper load tester and watched charging voltage on a scan tool, the alternator output was bouncing between 11.5–15.2 volts. Replacing the alternator and cleaning the main grounds fixed the issue and cleared P0560 for good.

Symptoms of P0560

  • Check engine light on: P0560 usually sets the MIL, sometimes along with a battery or charging warning light.
  • Battery/charging light: The battery symbol or “ALT/GEN” light may flicker or stay on.
  • Dim or flickering lights: Headlights, interior lights, and dash lights may dim, pulse, or change with engine speed.
  • Hard starting or no-start: Low system voltage can cause slow cranking or a complete no-crank condition.
  • Stalling or rough idle: The engine may stall at idle or run rough when voltage drops suddenly.
  • Electrical glitches: Radio resets, erratic gauges, power windows slowing down, or HVAC acting strange.
  • Transmission issues: On some cars, erratic shifting or going into limp mode when voltage is unstable.

Common Causes of P0560

Most Common Causes

  • Weak or failing battery: Old, sulfated, or partially shorted batteries can sag under load and trigger P0560.
  • Failing alternator: Worn brushes, bad diodes, or internal regulator failure cause low or unstable charging voltage.
  • Loose or corroded battery terminals: Poor connections at the battery posts create voltage drops and intermittent power.
  • Bad main ground connections: Corroded or loose engine/body grounds can cause the PCM to see incorrect voltage.
  • Damaged power cables: Frayed, corroded, or partially broken positive or ground cables between battery, alternator, and chassis.

Less Common Causes

  • Faulty ignition switch or power relay: Worn contacts can drop voltage feeding the PCM and main circuits.
  • Aftermarket accessories: Poorly installed audio systems, remote starts, or lighting can overload or disturb the charging system.
  • PCM internal fault: Rarely, the PCM’s internal voltage monitoring circuit or power supply fails.
  • Blown fusible link or high-resistance fuse: A partially burned fusible link can pass some current but cause low voltage under load.
  • Poor alternator control wiring: On smart charging systems, a bad sense wire or LIN/BSS control circuit can cause incorrect output and P0560.

Diagnosis: Step-by-Step Guide

You’ll want a basic digital multimeter (DMM), a good OBD-II scan tool (even a mid-range one works), and if possible a battery load tester. A wiring diagram or repair manual for your specific vehicle is also very helpful.

  1. Check battery condition visually. Look for swollen case, leaking acid, or obvious corrosion on terminals. Clean terminals and clamps if they’re crusty or green.
  2. Measure battery voltage engine off. With the engine off and key off, a healthy battery should read about 12.4–12.7 volts. Anything under ~12.2 volts suggests a low or weak battery.
  3. Measure charging voltage engine running. Start the engine and measure across the battery posts. Normal charging voltage is usually 13.5–14.7 volts. Below 13.0 or above ~15.0 volts is a red flag.
  4. Load test the battery. Use a proper load tester or have a parts store do it. A battery can show good voltage but fail under load and trigger P0560.
  5. Check for voltage drop on cables. With the engine running and electrical loads on (headlights, blower, rear defogger), measure voltage drop between battery positive and alternator output, and between battery negative and engine block. More than about 0.3–0.5 volts drop indicates a cable or connection issue.
  6. Inspect grounds and main connections. Check engine-to-chassis ground straps, body grounds, and alternator mounting/ground. Clean and tighten as needed.
  7. Scan live data. Use your scan tool to compare “system voltage” or “battery voltage” PID to what your multimeter shows. If the PCM reading is way off, there could be an internal PCM issue or wiring problem on the sense circuit.
  8. Check for related codes. Look for codes like P0562 (system voltage low) or P0563 (system voltage high). These can help narrow whether the alternator is undercharging or overcharging.
  9. Inspect alternator control circuit (if equipped). On vehicles with smart charging, check the sense wire, control wire, and related fuses/relays. A wiring diagram is essential here.
  10. Clear codes and retest. After any repair or cleaning, clear P0560 and test drive while monitoring voltage on the scan tool to confirm the fix.

Pro tip: Always test voltage directly at the battery posts, not just on the cable clamps. A clamp can be tight on a dirty post and give you misleading readings.

Possible Fixes & Repair Costs

Most P0560 fixes involve the battery, alternator, or wiring. Once you’ve tested properly, the actual repair is usually straightforward.

  • Replace weak battery: Common on older vehicles or ones with lots of short trips. Parts typically $120–$250 depending on size and brand, plus 0.3–0.5 hr labor if done at a shop.
  • Replace failing alternator: One of the most common fixes. Parts range from about $250–$700 for most vehicles, plus 1–3 hours labor depending on accessibility.
  • Clean or replace battery terminals/cables: Cleaning and tightening is often under $50 at a shop; replacing cables can run $100–$300 depending on complexity.
  • Repair grounds and power connections: Cleaning and reattaching ground straps is usually low cost; replacing corroded straps or lugs may add parts cost but is still relatively affordable.
  • Repair wiring or fusible links: Costs vary widely, typically $100–$400 depending on how buried the wiring is.
  • PCM replacement (rare): If the PCM is confirmed faulty, expect $600–$1,500+ including programming.

In most cases, you’re looking at a typical repair range of about $150–$900 for P0560, depending on whether it’s just a battery/connection issue or a full alternator replacement. Labor rates, vehicle design, and parts quality all affect the final bill.

Can I Still Drive With P0560?

You can often drive for a short time with P0560, but it’s risky. If the alternator is failing or the battery is on its way out, your car is basically running on borrowed time. Once the battery voltage drops too low, the ECU, ignition, and fuel system will shut down and the engine will stall. That can happen in traffic or far from home. If you notice dim lights, warning lights, or hard starting along with P0560, plan on diagnosing and repairing it as soon as possible rather than continuing to drive it daily.

What Happens If You Ignore P0560?

If you ignore P0560, the electrical system will likely get worse over time. You may start with a simple warning light and end up with a dead battery, repeated jump-starts, stalling on the road, or even damage to sensitive electronics if the alternator overcharges. Fixing it early usually saves money and avoids being stranded.

Related Codes

  • P0574 – Cruise Control System Vehicle Speed Too High
  • P0573 – Brake Switch “A” Circuit High
  • P0572 – Brake Switch “A” Circuit Low
  • P0571 – Brake Switch “A” Circuit
  • P0570 – Cruise Control Accelerate Signal
  • P0569 – Cruise Control Coast Signal
  • P0568 – Cruise Control Set Signal
  • P0567 – Cruise Control Resume Signal
  • P0566 – Cruise Control Off Signal
  • P0565 – Cruise Control On Signal

Key Takeaways

  • P0560 means the PCM is unhappy with system voltage, not that one specific part has failed.
  • Most causes are in the battery, alternator, or main power/ground connections.
  • Symptoms range from a simple warning light to stalling and no-start conditions.
  • Basic tools (multimeter and scan tool) can quickly narrow down the problem.
  • Fixing P0560 promptly prevents getting stranded and protects your vehicle’s electronics.

Vehicles Commonly Affected by P0560

P0560 can show up on almost any OBD-II vehicle, but in the field it’s especially common on certain makes and models. You’ll often see it on:

  • Domestic vehicles: Ford, Chevrolet, GMC, Dodge, Chrysler, and Jeep trucks and SUVs, especially as batteries and alternators age.
  • Japanese brands: Nissan, Honda, Toyota, and Subaru sedans and crossovers with original charging components past 8–10 years old.
  • European vehicles: BMW, Mercedes-Benz, Volkswagen, and Audi with smart charging systems that are sensitive to voltage drops and ground issues.
  • High-mileage fleets: Work trucks, delivery vans, and rideshare vehicles that see heavy electrical loads and frequent short trips.

FAQ

Can a bad battery cause code P0560?

Yes. A weak or internally damaged battery is one of the most common reasons for P0560. Even if your car still starts, a battery that drops voltage too much under load can trigger this code. Always load test the battery before replacing more expensive parts.

Is P0560 always an alternator problem?

No. While a failing alternator is a very common cause, P0560 can also be set by bad battery cables, poor grounds, a weak battery, or even wiring and PCM issues. Testing voltage and voltage drop is the only way to know for sure.

How do I clear P0560 after fixing the problem?

After repairing the underlying issue, use an OBD-II scan tool to clear the code. Then start the engine and monitor system voltage and drive the vehicle. If the voltage is stable and within spec, P0560 should not return. Some vehicles may clear the code on their own after several successful drive cycles.

Can I drive long distance with a P0560 code?

It’s not recommended. Long-distance driving with a charging or voltage issue can leave you stranded far from help. If you must drive, carry a jump pack and keep an eye on the battery/charging light and how the car behaves, but the safest move is to fix the issue before a long trip.

What’s the best first test for P0560 at home?

Start by measuring battery voltage with the engine off and then with the engine running. If the battery is low with the engine off, charge or test the battery. If the voltage is not in the 13.5–14.7 volt range with the engine running, suspect the alternator or connections. From there, inspect and clean battery terminals and grounds.