P00B6 — Radiator Coolant Temperature/Engine Coolant Temperature Correlation

P00B6 — Radiator Coolant Temperature/Engine Coolant Temperature Correlation. A fault in the engine cooling and temperature control. Short, gentle driving to a shop is usually possible. Typical causes: water pump or radiator issues, failed cooling fan or fan relay, low coolant level or air in the system.

powertrain (engine/transmission)

Is it safe to drive?

Caution: temperature correlation fault If the temperature gauge is steady and the engine is not overheating, P00B6 can usually be diagnosed without immediate driving. Avoid extended travel or heavy load until the fault is repaired, and stop the vehicle promptly if the gauge rises abnormally, a temperature warning appears, coolant is lost, or steam is visible.

Typical symptoms

Check Engine light illuminated with P00B6 stored as a confirmed or pending code
Engine temperature gauge reading unusually high, low, or unstable
Temperature readings disagree noticeably between the engine and radiator coolant sensors
Heater or air-conditioning outlet temperature does not match the selected temperature setting
Cooling fan cycles or operates inconsistently when P00B6 is present
Engine overheating, coolant loss, or an unusual temperature warning may occur, although P00B6 can also be present without visible symptoms

Common causes

Engine coolant temperature sensor with a drifted or internally damaged temperature element
Radiator coolant temperature sensor or switch whose signal does not correlate with the engine sensor
Open, shorted, corroded, or high-resistance wiring in either coolant-temperature sensor circuit
Poor electrical ground or a damaged connector affecting the coolant-temperature inputs
Incorrectly installed, mismatched, or improperly calibrated coolant-temperature sensor
Thermostat, coolant-flow, cooling-fan, or trapped-air condition producing an abnormal temperature difference

How to diagnose with an OBD scanner

Inspect the cooling system and sensor circuits With the engine cold, verify the coolant level, search for leaks, and inspect the engine and radiator coolant-temperature sensor connectors and wiring. Check for coolant contamination, damaged insulation, corrosion, or a loose connector. Do not disconnect components or remove the radiator cap while the system is hot and pressurized.
Read P00B6 with an OBD scanner Connect an ELM327 adapter and AIScanAuto or another scan tool, then read stored, pending, and freeze-frame data. Confirm whether P00B6 is active, identify any related sensor or circuit codes, and record freeze-frame information such as engine speed, coolant temperature, and operating conditions.
Compare both temperature signals live If the scanner can display both engine coolant temperature and radiator coolant temperature, compare them during a cold start and as the engine warms. Look for a frozen value, abrupt signal changes, or a difference outside the manufacturer-specified correlation tolerance. Remember that the two sensors may have a normal calibration offset.
Test the sensors and wiring Using the vehicle wiring diagram and a multimeter, test the engine and radiator coolant-temperature sensors for resistance at a known temperature. Verify connector pin condition, sensor ground, reference voltage, and continuity. A sensor resistance that does not match its specified temperature curve identifies a faulty sensor; damaged wiring requires repair rather than sensor replacement.
Verify thermostat and coolant flow Bleed trapped air, verify correct coolant concentration, pressure-test the system if leakage is suspected, and confirm that the thermostat and cooling fan operate as commanded. Incorrect coolant flow can create a radiator-to-engine temperature difference that causes P00B6 even when both sensors are electrically functional.
Repair, clear, and verify P00B6 Replace the faulty coolant-temperature sensor or repair the affected wiring and connector, then restore the specified coolant level. Clear P00B6 with the scan tool, drive through a complete warm-up cycle, and confirm that the code does not return while monitoring both temperature signals when available.

Approximate repair cost

A typical independent-shop estimate is about $150-$900 USD for P00B6 diagnosis and the required sensor, wiring, coolant, thermostat, or related cooling-system repair. These figures are estimates and vary by region.

Common questions

What does P00B6 specifically mean?

P00B6 means the engine coolant temperature signal and radiator coolant temperature signal are not correlating as expected. The fault may be in either sensor, its wiring, or the cooling system.

Can I drive with P00B6 stored?

You can cautiously drive to a repair shop if the engine temperature remains normal and there is no leak or overheating warning. Stop driving if the gauge climbs, coolant is disappearing, or the engine begins to overheat.

Which parts are commonly involved in P00B6?

Common causes include the engine coolant temperature sensor, radiator coolant temperature sensor or switch, damaged wiring, a bad connector, incorrect coolant level, trapped air, or thermostat and cooling-flow problems.

How is P00B6 diagnosed and confirmed?

A scan tool is used to read P00B6 and monitor both temperature inputs when available. The sensors, circuits, coolant level, thermostat, and fan are then checked, and the code is cleared and retested after repair.

When your check engine light comes on and a scan tool pulls code P00B6, the vehicle is telling you that something is wrong with the relationship between two temperature readings in the cooling system. Specifically, the engine's computer has detected a mismatch between what the radiator coolant temperature sensor is reporting and what the engine coolant temperature sensor is showing. These two sensors should tell roughly the same story during normal operation, and when they diverge beyond acceptable limits, P00B6 gets stored.

Modern engines rely on accurate temperature data to manage fuel delivery, cooling fan operation, and thermostat function. The Powertrain Control Module (PCM) continuously compares the signals from both temperature sensors. If the readings don't correlate as expected across multiple drive cycles, the PCM assumes a fault exists and logs P00B6 to alert you. The code also triggers the check engine light, serving as your invitation to investigate before the problem gets worse.

Think of these two sensors as a check-and-balance system. The radiator sensor monitors coolant temperature leaving the radiator, while the engine sensor measures coolant temperature near the engine block. When everything works properly, they track each other closely as the engine warms up and stabilizes. If one sensor starts reading too hot, too cold, or erratically while the other disagrees, the PCM flags the discrepancy and stores this diagnostic trouble code along with freeze frame data capturing the exact conditions at the moment of detection.

Common Symptoms of P00B6

The symptoms you'll notice with P00B6 stored depend partly on which sensor is lying and how badly. Here are the most frequently reported signs:

The cooling fans run continuously, even when the engine is at normal operating temperature
Cabin heating feels weak or nonexistent, especially in cold weather
The temperature gauge stays lower than normal or fails to climb to its usual operating range
Fuel economy drops noticeably because the engine runs richer than it should
In more severe cases, the gauge swings the other direction and you get an overheating warning
The check engine light remains illuminated until the fault clears

What Causes P00B6

The root causes typically trace back to a handful of common problem areas in the cooling system or its electrical connections:

Low coolant level or trapped air in the system creating temperature reading errors
A failing coolant temperature sensor giving inaccurate readings
A faulty cooling fan motor or fan relay preventing proper heat dissipation
Wiring problems such as damaged insulation, loose connectors, or corrosion in the sensor circuits
Water pump wear reducing coolant flow and causing temperature gradients
A clogged or leaking radiator disrupting normal heat exchange
A stuck thermostat affecting how quickly the system reaches operating temperature

The most likely culprit is usually a failing temperature sensor or low coolant, so those are worth investigating first before moving to more expensive components.

How to Diagnose P00B6

Follow these steps in order to pinpoint the cause without wasting money on unnecessary parts:

Connect an OBD2 scanner and confirm P00B6 is present. Record the freeze frame data showing RPM, engine load, coolant temperature, and vehicle speed at the time of failure—this tells you exactly what conditions triggered the code.
Scan for any other stored codes. Related faults in the cooling system, sensor circuits, or fan controls often point to the real problem. Also check for any manufacturer TSBs (Technical Service Bulletins) specific to your make and model—many common P0xxx codes have known factory fixes or software updates documented.
Perform a thorough visual inspection of all wiring and connectors tied to the engine cooling and temperature monitoring circuits. Look for chafed wires, bent pins, moisture intrusion, or loose connections that could cause erratic sensor behavior.
Monitor live data from both temperature sensors while the engine warms up. They should rise smoothly and track closely together until reaching operating temperature. A sensor that jumps, lags, or reads stuck at one value indicates failure.
Check the coolant level in the overflow tank and radiator. Inspect the upper and lower radiator hoses by feel—proper thermostat operation produces a warm upper hose and cooler lower hose once the engine reaches temperature.
Clear the code and complete a full drive cycle that reproduces the freeze frame conditions. If P00B6 returns, you have confirmed an active fault and can proceed with component testing or replacement.

Repair Options and Costs

Once you've isolated the failing component, here are typical repair costs for the most common fixes associated with P00B6:

Replacing the coolant temperature sensor typically runs $100–$300 including parts and labor
Replacing the thermostat generally costs $150–$400 depending on your vehicle and local rates
Cooling system repairs involving the water pump, cooling fan, or radiator usually range from $300–$1,200

Always start with the cheapest probable cause (the sensor) before committing to major cooling system work. An accurate diagnosis upfront prevents spending $1,000 on a new radiator when a $150 thermostat or $100 sensor was the real issue all along.

Can You Drive with P00B6?

Proceed with caution if the code is stored but no overheating is occurring. A thermostat that stays open (causing the engine to run cool) will mainly hurt your fuel economy and may not cause immediate damage. However, watch your temperature gauge closely and pull over immediately if it climbs into the red zone. Driving even a short distance with an actually overheating engine can destroy head gaskets, warp cylinder heads, or cause complete engine failure. If your gauge is already running hot or you see steam, do not drive—call for a tow instead.