What Error 502 Means

Error 502 signals a fault in the drive unit integrated lighting output. Bosch motors include a dedicated 6V DC lighting output for the integrated front and rear lights. When this circuit detects a short, open circuit, or overload, error 502 is raised. Motor assistance is typically not affected.

Common Causes

  1. Broken or disconnected light cable — The thin cable to the headlight is vulnerable to damage from cable ties, frame rub, or impact.
  2. Failed LED driver or bulb — An internal fault in the headlight unit can present as a short circuit.
  3. Water in a light connector — Moisture bridging pins creates a resistance fault.
  4. Disconnected rear light — Many setups wire the rear light in series. A failed rear light breaks the circuit.

Fix Procedure

Step 1: Inspect All Light Connectors

Trace the lighting cable from motor to front and rear light. Disconnect and reconnect each connector. Look for corrosion, broken wires, and cracked insulation.

Step 2: Disconnect the Light Temporarily

Disconnect the front light cable from the motor and power on. If error 502 clears, the fault is in the light unit or its cable.

Step 3: Replace the Faulty Light Unit

Replace the faulty unit and verify error 502 clears on the next power cycle.