P128A - Cylinder Head Temperature Sensor Circuit Intermittent/Erratic

Repair Importance Level: 3/3
Repair Difficulty Level: 3/3    What is this?
Table of contents

P128A Possible Causes

  • Wrong thermostat
  • Not at operating range
  • Engine overheated
  • Low engine coolant level
  • Faulty Cylinder Head Temperature (CHT) sensor
  • Cylinder Head Temperature (CHT) sensor harness is open or shorted
  • Cylinder Head Temperature (CHT) sensor circuit poor electrical connection

How do I fix code P128A?

Check the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.

Cost of diagnosing the P128A code

Labor: 1.0

The cost of diagnosing the P128A code is 1.0 hour of labor. The auto repair labor rates vary by location, your vehicle's make and model, and even your engine type. Most auto repairs shops charge between $75 and $150 per hour.

Possible Symptoms

  • Engine Light ON (or Service Engine Soon Warning Light)

P128A Description

The Cylinder Head Temperature (CHT) Sensor is mounted into the wall of the cylinder head and is not connected to any coolant passages. The CHT sends a signal to the Powertrain Control Module (PCM) indicating the cylinder head temperature. If the temperature exceeds 126°C (-258°F), the PCM disables four fuel injectors at a time. The PCM will alternate which four injectors are disabled every 32 engine cycles. The four cylinders that are not being fuel injected act as air pumps to aid in cooling the engine. If the temperature exceeds 154 °C (310°F), the PCM disables all of the fuel injectors until the engine temperature drops below 154°C (310°F).
OBDII Code P128a - Cylinder Head Temperature Sensor Circuit Intermittent/Erratic - AutoCodes.com

More Information

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Information for specific makes

  • P128A BMW Nitrogen Oxide Sensor Regeneration Nitrogen Oxide Cat Regeneration Monitoring
  • P128A BUICK Fuel Rail Pressure Sensor 1 Internal Performance
  • P128A CADILLAC Fuel Rail Pressure Sensor 1 Internal Performance
  • P128A CHEVROLET Fuel Rail Pressure Sensor 1 Internal Performance
  • P128A FORD Cylinder Head Temperature Sensor Circuit Intermittent/Erratic
  • P128A GMC Fuel Rail Pressure Sensor 1 Internal Performance
  • P128A LINCOLN Cylinder Head Temperature Sensor Circuit Intermittent/Erratic
  • P128A MERCURY Cylinder Head Temperature Sensor Circuit Intermittent/Erratic
  • P128A MINI Nitrogen Oxide Sensor Regeneration Nitrogen Oxide Cat Regeneration Monitoring

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