OBD Guide
ENFRDEESPT

P121C

Cylinder Balance Test Injector Leaking

P121C is an OBD-II diagnostic trouble code meaning: Cylinder Balance Test Injector Leaking. Common causes: worn injector o-rings, dirty or clogged nozzle. Estimated repair cost: $17–56.

Severity
⚠️ Medium
Can you drive?
Yes, but get it checked soon
Approx. repair cost
$17–56 (est.)

Symptoms

  • Uneven engine operation
  • Increased fuel consumption
  • Smell of gasoline from the exhaust pipe
  • Dips during acceleration
  • Increased CO emissions

Causes

  • Worn injector o-rings
  • Dirty or clogged nozzle
  • Mechanical damage to the injector
  • Problems with the fuel system (high pressure)
  • Injector electrical circuit malfunction

How to Fix

  1. Check the condition of the nozzle and its seals
  2. Clean or replace the nozzle if necessary
  3. Check the pressure in the fuel system
  4. Check the injector electrical circuit
  5. Replace injector O-rings

Related codes

P121DP121BP121A

FAQ

What does the P121C code mean?

P121C is an OBD-II diagnostic trouble code that indicates: Cylinder Balance Test Injector Leaking

What causes a P121C error code?

The most common causes of P121C include: Worn injector o-rings; Dirty or clogged nozzle; Mechanical damage to the injector; Problems with the fuel system (high pressure).

How do I fix a P121C diagnostic trouble code?

To fix P121C: Check the condition of the nozzle and its seals. Clean or replace the nozzle if necessary. Check the pressure in the fuel system. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with P121C?

Yes, but get it checked soon

How much does it cost to fix P121C?

The estimated repair cost for P121C is $17–56. Actual cost depends on your vehicle, location, and labor rates.

FRDEESPT

See also: Russian version · NationStat