OBD Guide
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P121F

Nitrogen Oxide Sensor Linear Oxygen Sensor Short Circuit

P121F is an OBD-II diagnostic trouble code meaning: Nitrogen Oxide Sensor Linear Oxygen Sensor Short Circuit. Common causes: damaged nox sensor wiring harness, short circuit in the sensor circuit. Estimated repair cost: $56–167.

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

Symptoms

  • Check Engine light comes on
  • Deterioration of vehicle dynamics
  • Increased fuel consumption
  • Problems with passing environmental control
  • Possible misfires

Causes

  • Damaged NOx sensor wiring harness
  • Short circuit in the sensor circuit
  • Malfunction of the NOx sensor itself
  • Sensor connection problems
  • Corrosion of contacts or connectors

How to Fix

  1. Check the integrity of the sensor wiring harness
  2. Inspect connectors and contacts for corrosion
  3. Check sensor resistance
  4. Replace NOx sensor if necessary
  5. Reset the error and check the system operation

Related codes

P121EP1220P1221

FAQ

What does the P121F code mean?

P121F is an OBD-II diagnostic trouble code that indicates: Nitrogen Oxide Sensor Linear Oxygen Sensor Short Circuit

What causes a P121F error code?

The most common causes of P121F include: Damaged NOx sensor wiring harness; Short circuit in the sensor circuit; Malfunction of the NOx sensor itself; Sensor connection problems.

How do I fix a P121F diagnostic trouble code?

To fix P121F: Check the integrity of the sensor wiring harness. Inspect connectors and contacts for corrosion. Check sensor resistance. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with P121F?

Yes, but get it checked soon

How much does it cost to fix P121F?

The estimated repair cost for P121F is $56–167. Actual cost depends on your vehicle, location, and labor rates.

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See also: Russian version · NationStat