OBD Guide
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C1840

Air Suspension Disable Switch Circuit Failure

C1840 is an OBD-II diagnostic trouble code meaning: Air Suspension Disable Switch Circuit Failure. Common causes: open or shorted wiring harness, air suspension cut-off switch malfunction. Estimated repair cost: $33–167.

Severity
⚠️ Medium
Can you drive?
Limited driving only, diagnose soon
Approx. repair cost
$33–167 (est.)

Symptoms

  • The suspension warning light is on
  • Air suspension does not disengage when switch is pressed
  • The suspension may not work correctly or turn off spontaneously

Causes

  • Open or shorted wiring harness
  • Air suspension cut-off switch malfunction
  • Problems with the suspension control module
  • Poor contact in connectors
  • Short circuit to ground or power

How to Fix

  1. Check the condition of the wiring harness to the switch
  2. Check the operation of the switch with a multimeter
  3. Inspect connectors for oxidation or damage
  4. Check the presence of power and ground in the circuit
  5. Diagnose the suspension control module

Related codes

C1830C1835C1845

FAQ

What does the C1840 code mean?

C1840 is an OBD-II diagnostic trouble code that indicates: Air Suspension Disable Switch Circuit Failure

What causes a C1840 error code?

The most common causes of C1840 include: Open or shorted wiring harness; Air suspension cut-off switch malfunction; Problems with the suspension control module; Poor contact in connectors.

How do I fix a C1840 diagnostic trouble code?

To fix C1840: Check the condition of the wiring harness to the switch. Check the operation of the switch with a multimeter. Inspect connectors for oxidation or damage. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with C1840?

Limited driving only, diagnose soon

How much does it cost to fix C1840?

The estimated repair cost for C1840 is $33–167. Actual cost depends on your vehicle, location, and labor rates.

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See also: Russian version · NationStat