Charging and starting codes

The alternator (generator) keeps the battery charged and powers the car while the engine runs, and on most newer cars the engine computer controls its output. The starter cranks the engine through a relay the computer or ignition switch controls. Charging faults can drain the battery until the car stalls; starting faults usually show up as a no-crank.

How these codes differ

• Generator control codes (P0620 for the generator control circuit, P0621 for the warning lamp or L-terminal circuit, P0622 for the field or F-terminal circuit, and P2500 and P2501 for the L-terminal circuit low or high) concern the wires and signals between the computer and the alternator's regulator. They point to wiring and connectors before the alternator itself.
• Starter relay codes (P0615 circuit, P0616 low, P0617 high) concern the circuit the computer uses to engage the starter. A fault here usually means no crank, while the battery and lights still work.
• System voltage codes (P0562 low and P0563 high) report what the computer actually saw. They sit with the speed and idle group on this site, but they often have a charging cause. Testing the battery first matters: a weak battery can make a good alternator look bad.
• A charging warning light while driving means the battery is not being charged, so the car is running on battery power that will run out. That is more urgent than a code stored with no light.

Codes that show up together

• A charging fault together with warnings from steering or other modules: low voltage can reduce electric power steering assist and makes several modules log faults, so the charging problem is checked first.

Charging and starting codes

• P1682

  Engine computer’s two ignition voltage feeds disagree (GM)

  Severity: Inspect soon

• P1604

  Startability malfunction (Toyota and Subaru)

  Severity: Inspect soon

• P2535

  Ignition switch run/start signal reading high

  Severity: Monitor

• P0560

  The computer sees system voltage outside the range it expects

  Severity: Severity not verified

• P0561

  The computer sees system voltage that is not steady

  Severity: Severity not verified

• P0563

  The computer sees system voltage that is too high

  Severity: Severity not verified

• P0615

  Problem in the starter relay circuit

  Severity: Inspect soon

• P0620

  Generator (alternator) control circuit fault: the engine computer sees a problem in the circuit that controls how much the alternator charges

  Severity: Inspect soon

• P0622

  Alternator field control circuit fault: the engine computer sees a bad signal on the wire that tells the alternator how hard to charge

  Severity: Inspect soon

• P2534

  Voltage on the ignition switch run/start circuit read by the computer is too low

  Severity: Severity not verified

• P0621

  Generator (alternator) warning lamp control circuit is faulty

  Severity: Inspect soon

Sources and review

1. Service work on the charging system: battery and generator testing for vehicles with start-stop systems — HELLA TechWorld
2. 2003 Acura MDX Owner's Manual: Instruments and Controls, indicator lights — American Honda Motor Co.
3. Kia owner's manual (2024, web edition KA4): Electric power steering (EPS) — Kia America

Last reviewed

October 16, 2026

Written by

Saurabh K.

Editorial review

Pending

Technician review

Technician review pending

This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error