Error Code P2181 is a Cooling System Performance Code.

This error code is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system, especially those made since 1996 up to present. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model to another. It is, however, more common among Audi, Dodge, Chrysler, Jeep, Volkswagen, etc.


Unlike many generic codes, however, this code is relatively specific as to other areas or items the fault occurred. Also, it’s quite vague, because when it’s recognized, that means the engine temperature is out of range, but it could mean too hot or too cold.

Other cooling systems=related error codes include:

Common Symptoms

As with other codes, this code activates the Check Engine light and registers the code to the vehicle’s memory system. Other symptoms include:

  • Overheating
  • Engine not reaching the right operating temperature

Possible Causes

The two most common causes of this code include the cooling system of the engine:

  • Defective water pump
  • Faulty thermostat

How to Check

Diagnosing this code is much like diagnosing for overheat engine. First, technicians plug in the OBD scanner and turn the key on to check for further codes. There will be a coolant temperature sensor code that will cause the radiator fans to malfunction.

When the engine is still cold, remove the radiator cap and check the coolant level. With the pressure tester, check for leaks in the system. This includes all the components around the radiator, hoses, block, intake, and heater core.

If the engine temperature is normal while driving but overheats at a stop, that means the radiator fan is malfunctioning.

Technicians will then check the serpentine belt-tension for proper tension. Faulty belt tensioners are common and allow belt slip. They will also check for leaks around the water pump. For those driven by the timing belt, coolant leaks out of the bottom of the belt cover. If the water pump is exposed, they will check the pulley for wobble indicating a worn water pump bushing.

Next, they check the engine driven fan for wobbling and leakage around the clutch. The fan will be rotated by hand; a good fan clutch will have some resistance. A specifically slow moving fan with engine running means the fan clutch has gone bad.

Next, they will check the coolant level sensor on the side of the radiator referring to the service manual.

If the vehicle has a radiator cap, they will have to leave it off and start the engine to allow it to warm. They monitor the engine temperature with the scan tool and as the temperature approaches 190˚ watch for coolant to begin flowing from the inside radiator cores. If no flow is detected above 19 ˚, replace the cap and shut off the motor. The thermostat is defective.

If the radiator begins to flow, replace the cap and allow the engine to reach 205˚ before shutting it off. If the electric fans do not come on, shut the engine off.

Next, technicians will check the engine fan fuse and relays in the fuse and relay box on the driver’s side fender well. Their location is listed on the underside of the cover.

Then, they will check the operation of the fan by disconnecting the wiring pigtail. Then they will place a jumper from the ground terminal to a good ground and power terminal to the battery. If the fan fails to operate, then it must be replaced. If it operates, check the wiring at the fuse block and coolant temperature sensor for loose connections, pushed out connector pins or burnt wiring.

Lastly, they will check for a blown head gasket

How to Fix

Error Code P2181 can be a complex code to repair, thus it requires a thorough diagnosis to identify the exact cause of the code and the right repair procedure. Common repairs for this code include:

  • Replacement of the thermostat
  • Repair or replacement of hoses that has leaks and blockage
  • Repair or replacement of radiator fan
  • Repair or replacement of fan clutch
  • Replacement of the radiator cap
  • Replacement of fan
  • Repair or replacement of defective wiring and connectors at the fuse block and coolant temperature sensor
  • Replacement of head gasket

This code generally means the vehicle is having a cooling system performance problem, which can generally be fixed by simply replacing the thermostat.