P058D

What it means

P058D means the engine control unit has found a performance problem with the voltage monitoring function of the battery monitor module. The module reports battery voltage, and what it reports does not agree with expected values or with other voltage readings the control unit has. It does not on its own say whether the battery, the module, its wiring or the charging system is at fault.

Symptoms

• Battery or charging warning light on the dashboard
• Engine management light on
• Slow cranking or intermittent hard starting
• Stop-start system disabled or not working
• Flickering lights or erratic electrical behaviour
• Charging system behaving oddly, such as low or fluctuating voltage

Possible causes

• Weak, discharged or ageing battery giving unstable or implausible voltage readingslikely
• Loose, corroded or poorly earthed battery terminals, or a poor connection at the battery monitor modulelikely
• Damaged wiring or connector between the battery monitor module and the control unit, including a communication or supply faultpossible
• Faulty battery monitor module giving incorrect voltage readingspossible
• Charging system fault, such as a failing alternator or regulator, causing voltage outside the expected rangepossible
• Software or calibration fault in the control unit or module, where a known update exists for the vehiclerare

How to diagnose

1. Read all stored codes and freeze frame data, and note any charging, battery, communication or low voltage codes alongside P058D.
2. Visually inspect the battery terminals, clamps, earth strap and the monitor module connector for corrosion, looseness, heat damage or fluid ingress.
3. Measure battery resting voltage, then test the battery condition with a suitable load or conductance test.
4. Check charging voltage at the battery with the engine running and with electrical loads on, and compare it with the manufacturer's specification.
5. Check the module's supply, earth and signal or data wiring for continuity, shorts and voltage drop, following the wiring diagram for the model.
6. Compare the voltage reported by the module in live data with a measured value at the battery.
7. Check for relevant technical bulletins or software updates for the vehicle, as the monitor module's location and behaviour vary by model.
8. Clear the code after repair and road test to confirm it does not return.

How to fix

• Clean and tighten the battery terminals and earth connections, and repair any corroded or damaged terminal.
• Replace the battery if it fails testing, and carry out any battery registration or reset procedure the manufacturer requires.
• Repair or replace damaged wiring or connectors in the monitor module circuit.
• Replace the battery monitor module if it gives wrong readings with a good battery and wiring.
• Repair or replace the alternator or regulator if the charging voltage is out of range.
• Apply a manufacturer software update only if the fault is a known calibration issue for that vehicle.

Can I keep driving?

Nearby codes

• P058CGenericBattery Monitor Module Temperature Monitoring Performance
• P058EGenericBattery Monitor Module Temperature Too High