OBD Guide
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P1278

Air Fuel Ratio Sensor 1 Bank 1 Circuit Slow Response

P1278 is an OBD-II diagnostic trouble code meaning: Air Fuel Ratio Sensor 1 Bank 1 Circuit Slow Response. Common causes: air-fuel ratio sensor malfunction, sensor contamination. Estimated repair cost: $33–89.

Severity
⚠️ Medium
Can you drive?
Yes, but get it checked soon
Approx. repair cost
$33–89 (est.)

Symptoms

  • Increased fuel consumption
  • Reduced engine power
  • Unstable idling
  • Check Engine Light Is On
  • Increased emissions of harmful substances

Causes

  • Air-fuel ratio sensor malfunction
  • Sensor contamination
  • Problems in the sensor electrical circuit
  • Wiring harness fault
  • Sensor circuit grounding problems

How to Fix

  1. Check the condition of the AFR sensor
  2. Check the electrical circuit of the sensor for breaks and short circuits
  3. Clean sensor connector contacts
  4. Check sensor circuit grounding
  5. If necessary, replace the air-fuel ratio sensor

Related codes

P1275P1276P1277

Error P1278 by Vehicle Brand

BuickCadillacChevroletChryslerFordGMGMCLincolnMercuryOldsmobileSaturn

FAQ

What does the P1278 code mean?

P1278 is an OBD-II diagnostic trouble code that indicates: Air Fuel Ratio Sensor 1 Bank 1 Circuit Slow Response

What causes a P1278 error code?

The most common causes of P1278 include: Air-fuel ratio sensor malfunction; Sensor contamination; Problems in the sensor electrical circuit; Wiring harness fault.

How do I fix a P1278 diagnostic trouble code?

To fix P1278: Check the condition of the AFR sensor. Check the electrical circuit of the sensor for breaks and short circuits. Clean sensor connector contacts. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with P1278?

Yes, but get it checked soon

How much does it cost to fix P1278?

The estimated repair cost for P1278 is $33–89. Actual cost depends on your vehicle, location, and labor rates.

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