01 General Motors: A History of Innovation and Leadership • 02 Starter Motor: Functions, Parts, Troubleshooting, and Commo… • 03 You Might Stall On The Highway If You Keep Ignoring That Ra… • 04 A Watch Collector Spent $49.4 Million on Four Rolexes and t… • 05 Fix That Check Engine Light Today: 5 Simple Sensor Cleaning… • 06 Can a Hybrid Car Survive a Flood? Understanding the Risks a… • 07 Thinking of Upgrading to LED Headlights? Here's What You Mu… • 08 C0035 - Left Front Wheel Speed Circuit Malfunction • 09 Why Resetting ECU Without Fixing Root Cause Always Backfires • 10 Unlocking the Power of Differential Lock: Traction, Problem… •

DTC codes / P00xx · Fuel and air metering and auxiliary emission controls / P00B6

P00B6Radiator Coolant Temperature/Engine Coolant Temperature Correlation

P00B6 indicates that the powertrain control module (PCM) has detected a mismatch between the radiator coolant temperature sensor and the engine coolant temperature sensor readings when the engine is running. The computer expects these two sensors to report similar temperatures once the engine has warmed and the thermostat has opened, so a sustained difference sets this correlation code.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering and auxiliary emission controls

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms
  • Temperature gauge reading that fluctuates or sits lower than normal
  • Poor heater performance or lukewarm air from the vents
  • Cooling fans running constantly or not engaging when expected
  • Slightly reduced fuel economy or rough running during warm-up
  • Overheating in severe cases if coolant flow is restricted

Common causes, most likely first

  1. Faulty radiator coolant temperature sensor or damaged wiring to it
  2. Faulty engine coolant temperature sensor giving skewed readings
  3. Low coolant level or trapped air in the cooling system
  4. Sticking or incorrectly rated thermostat
  5. Restricted radiator flow or a partially blocked coolant passage
  6. Corroded or chafed sensor connector pins causing intermittent signals
  7. PCM software calibration issue or internal fault in the temperature input circuit

How to diagnose and fix it

  1. Check coolant level and inspect for leaks, then bleed any air from the cooling system
  2. Use a scan tool to compare live radiator and engine coolant temperature readings during warm-up
  3. Inspect the radiator temperature sensor connector and wiring for corrosion, chafing, or loose pins
  4. Test both coolant temperature sensors with a multimeter against the manufacturer's resistance chart
  5. Verify thermostat operation by monitoring coolant temperature rise and upper hose temperature
  6. Check for radiator restriction or poor coolant flow with an infrared thermometer across the core
  7. Replace the faulty sensor or repair wiring, clear the code, and verify correlation during a road test

Correlation codes often mislead parts swappers

  • A low coolant level or air pocket can create a temperature split between the two sensors without either sensor being defective, so always bleed the system before replacing parts.
  • The radiator coolant temperature sensor is frequently located in the lower tank or outlet hose, where it reads cooler than the engine sensor until the thermostat opens, so testing must be done at full operating temperature.
  • A sticking thermostat can mimic a failed radiator sensor because the radiator stays cold while the engine warms, producing the exact correlation error the PCM flags.
  • Aftermarket thermostats with the wrong opening temperature are a common cause of persistent P00B6 codes that return after sensor replacement.
  • This code does not always mean a sensor has failed; wiring harness chafing near the radiator support or fan shroud often interrupts the signal intermittently.

Can I keep driving with P00B6?

You can usually drive short distances at moderate speed, but avoid heavy loads and long trips until the fault is diagnosed because a cooling system problem can escalate to overheating. Stop driving immediately if the temperature gauge climbs into the red or you see steam.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage