OBD Guide
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B2020

Open In Left Side Upper MOS

B2020 is an OBD-II diagnostic trouble code meaning: Open In Left Side Upper MOS. Common causes: broken wire in the harness, mos device malfunction. Estimated repair cost: $56–167.

Severity
⚠️ Medium
Can you drive?
Do not drive — repair immediately
Approx. repair cost
$56–167 (est.)

Symptoms

  • Comfort or safety system malfunction
  • The indicator light on the dashboard comes on
  • Failure of related components

Causes

  • Broken wire in the harness
  • MOS device malfunction
  • Poor contact in the connector
  • Short circuit in the circuit
  • Damage to the control unit

How to Fix

  1. Check the integrity of the wiring harness
  2. Check the contacts in the connectors
  3. Check the functionality of the MOS device
  4. Check the control unit for damage
  5. Replace faulty components

Related codes

B2021B2022B2023

FAQ

What does the B2020 code mean?

B2020 is an OBD-II diagnostic trouble code that indicates: Open In Left Side Upper MOS

What causes a B2020 error code?

The most common causes of B2020 include: Broken wire in the harness; MOS device malfunction; Poor contact in the connector; Short circuit in the circuit.

How do I fix a B2020 diagnostic trouble code?

To fix B2020: Check the integrity of the wiring harness. Check the contacts in the connectors. Check the functionality of the MOS device. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with B2020?

Do not drive — repair immediately

How much does it cost to fix B2020?

The estimated repair cost for B2020 is $56–167. Actual cost depends on your vehicle, location, and labor rates.

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See also: Russian version · NationStat