OBD Guide
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B1840

Driver Seat Lumbar Up Switch Circuit

B1840 is an OBD-II diagnostic trouble code meaning: Driver Seat Lumbar Up Switch Circuit. Common causes: lumbar support switch malfunction, open or short circuit in wiring harness. Estimated repair cost: $33–111.

Severity
✅ Low
Can you drive?
Do not drive — repair immediately
Approx. repair cost
$33–111 (est.)

Symptoms

  • Driver's seat lumbar support adjustment does not work
  • Malfunction indicator on the dashboard
  • Saving error code after reset

Causes

  • Lumbar support switch malfunction
  • Open or short circuit in wiring harness
  • Poor contact in connectors
  • Contact corrosion
  • Seat control module malfunction

How to Fix

  1. Check the operation of the lumbar support switch
  2. Inspect the wiring harness for damage
  3. Check connections and contacts in connectors
  4. Test circuit resistance
  5. If necessary, replace the switch or repair the harness
  6. Reset the error code and check if it returns

Related codes

B1841B1842B1830

FAQ

What does the B1840 code mean?

B1840 is an OBD-II diagnostic trouble code that indicates: Driver Seat Lumbar Up Switch Circuit

What causes a B1840 error code?

The most common causes of B1840 include: Lumbar support switch malfunction; Open or short circuit in wiring harness; Poor contact in connectors; Contact corrosion.

How do I fix a B1840 diagnostic trouble code?

To fix B1840: Check the operation of the lumbar support switch. Inspect the wiring harness for damage. Check connections and contacts in connectors. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with B1840?

Do not drive — repair immediately

How much does it cost to fix B1840?

The estimated repair cost for B1840 is $33–111. Actual cost depends on your vehicle, location, and labor rates.

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See also: Russian version · NationStat