OBD Guide
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B1865

Battery Power Supply ECU Circuit Open

B1865 is an OBD-II diagnostic trouble code meaning: Battery Power Supply ECU Circuit Open. Common causes: broken wire in the wiring harness, oxidation or damage to contacts in connectors. Estimated repair cost: $56–167.

Severity
🚨 Critical
Can you drive?
Yes, but get it checked soon
Approx. repair cost
$56–167 (est.)

Symptoms

  • Engine won't start
  • ECU does not respond to diagnostics
  • Spontaneous shutdown of electronics
  • Check Engine Light Is On

Causes

  • Broken wire in the wiring harness
  • Oxidation or damage to contacts in connectors
  • Blown fuse
  • ECU power relay malfunction
  • Short circuit in power supply

How to Fix

  1. Check the condition of fuses and relays related to ECU power supply
  2. Inspect the wiring harness and connectors for damage.
  3. Check the voltage at the ECU terminals with the ignition on
  4. If necessary, replace damaged wires or connectors
  5. Reset the error and check if it appears again

Related codes

B1866B1867U0100

FAQ

What does the B1865 code mean?

B1865 is an OBD-II diagnostic trouble code that indicates: Battery Power Supply ECU Circuit Open

What causes a B1865 error code?

The most common causes of B1865 include: Broken wire in the wiring harness; Oxidation or damage to contacts in connectors; Blown fuse; ECU power relay malfunction.

How do I fix a B1865 diagnostic trouble code?

To fix B1865: Check the condition of fuses and relays related to ECU power supply. Inspect the wiring harness and connectors for damage.. Check the voltage at the ECU terminals with the ignition on. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with B1865?

Yes, but get it checked soon

How much does it cost to fix B1865?

The estimated repair cost for B1865 is $56–167. Actual cost depends on your vehicle, location, and labor rates.

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See also: Russian version · NationStat