OBD Guide
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B1D78

Auxiliary Input Circuit Open

B1D78 is an OBD-II diagnostic trouble code meaning: Auxiliary Input Circuit Open. Common causes: broken wire in the harness, oxidation or corrosion of contacts. Estimated repair cost: $22–111.

Severity
⚠️ Medium
Can you drive?
Limited driving only, diagnose soon
Approx. repair cost
$22–111 (est.)

Symptoms

  • Incorrect operation of additional devices
  • Lack of response to commands from the remote control or buttons
  • The malfunction indicator on the dashboard lights up

Causes

  • Broken wire in the harness
  • Oxidation or corrosion of contacts
  • Option malfunction
  • Connector damage

How to Fix

  1. Check the integrity of the wiring harness
  2. Inspect contacts for oxidation
  3. Check the functionality of the additional device
  4. Replace damaged wires or connectors

Related codes

B1D79B1D80

FAQ

What does the B1D78 code mean?

B1D78 is an OBD-II diagnostic trouble code that indicates: Auxiliary Input Circuit Open

What causes a B1D78 error code?

The most common causes of B1D78 include: Broken wire in the harness; Oxidation or corrosion of contacts; Option malfunction; Connector damage.

How do I fix a B1D78 diagnostic trouble code?

To fix B1D78: Check the integrity of the wiring harness. Inspect contacts for oxidation. Check the functionality of the additional device. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with B1D78?

Limited driving only, diagnose soon

How much does it cost to fix B1D78?

The estimated repair cost for B1D78 is $22–111. Actual cost depends on your vehicle, location, and labor rates.

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See also: Russian version · NationStat