What Does P1486 Honda Accord Mean And What To Do When This Trouble Code Comes Up?

The code P1486 on a Honda Accord usually indicates a problem with the thermostat or the engine coolant temperature (ECT) sensor. Repairing the thermostat or ECT sensor and clearing the codes usually solves the problem.

The P1486 Honda Accord error code can be concerning, but this guide will walk you through the meaning of the code, potential causes, troubleshooting steps, and tips for dealing with it correctly. P1486 can often be repaired without visiting a mechanic if you have some basic mechanical skills and the right information.

Honda P1486 Code Definition: Cooling System Malfunction

The P1486 code is classified as a generic powertrain diagnostic trouble code (DTC). It indicates there is an issue detected in the engine cooling system.

Specifically, P1486 means:

The PCM monitors engine temperature using an Engine Coolant Temperature (ECT) sensor. It is a two-wire thermistor whose resistance and signal voltage vary with engine temperature.

This signal is used by the PCM to control fuel injection, ignition timing, idle speed, and other functions. The transmission control module also uses it for shift timing and quality.

If the PCM detects that the engine has not reached the proper operating temperature after startup, it will record a P1486 DTC and illuminate the check engine light.

What Are The Possible Causes Of The P1486 Code On Honda Accords?

There are a few different issues that can trigger the P1486 Honda Accord trouble code:

  1. Thermostat Problems
  2. Coolant System Leaks
  3. Engine Coolant Temperature Sensor
  4. Radiator Fan Problems
  5. Thermostat Monitor Failure

Thermostat Problems

A faulty thermostat is the most common cause of P1486 on Honda Accords. The thermostat regulates coolant flow and engine operating temperature by opening and closing. If it does not close properly, the engine will take longer to warm up, causing the code to be set.

The most likely cause is a stuck open thermostat, but a thermostat that leaks internally can also cause P1486. If the thermostat is faulty, replacing it will usually solve the problem.

Coolant System Leaks

Any leak in the cooling system can allow coolant to escape, preventing the engine from reaching an optimal operating temperature. Check for leaks in all hoses, gaskets, the radiator, and the water pump. If necessary, refill the coolant.

What Are The Possible Causes Of The P1486 Code On Honda Accords
What Are The Possible Causes Of The P1486 Code On Honda Accords

Engine Coolant Temperature Sensor

The ECT sensor could be sending incorrect readings to the ECM due to a wiring issue or failure of the sensor itself. This can cause the P1486 code even with no other cooling system faults present. Inspect sensor wiring for damage and test or replace the sensor as needed.

Radiator Fan Problems

If the radiator cooling fan runs continuously or fails to turn on, it can affect the engine’s ability to warm up properly. Test fan operation and relay function to rule it out as the cause.

Thermostat Monitor Failure

In rare cases, the ECM’s thermostat monitor function may set P1486 erroneously, with no actual overcooling present. This may require ECM reprogramming or replacement if no other faults are found.

Honda Tech Notes For P1486 Code

In addition to my own experience diagnosing P1486 on Honda Accords, Honda has released some technical service bulletins related to this trouble code:

  1. On the 2000-2001 Accords and 2001-2002 Civics, P1486 is considered equivalent to code P0128 by Honda for diagnosis. The codes point to the same cooling system faults.
  2. Due to the similarity between P1486 and P0128, Honda has seen cases where the scanner tool shows one code while the other is actually stored in the ECM. Always check for both if either is present.
  3. TSB 01-022 requires ECM replacement in some cases if no faults are found with the thermostat or ECT sensor, indicating an ECM programming issue.

How Do I Find The Thermostat On A Honda Accord?

Since a sticking open thermostat is the most common cause of P1486 Honda Accord, locating it is key for inspection and replacement. Here are steps to find it:

  1. Follow the upper radiator hose from the radiator toward the engine. This hose carries hot coolant from the engine to the radiator.
  2. Near the engine, the hose will connect to a short, flattened section before connecting to the engine. This is the thermostat housing.
  3. The thermostat is contained inside this housing. Remove the two 10mm bolts to separate the housing and access the thermostat.
  4. Visually inspect the thermostat and seals for signs of failure. A green or corroded thermostat indicates it should be replaced.

Is It Safe To Drive With The P1486 Code On A Honda Accord?

The P1486 Honda Accord trouble code does not indicate an immediate safety hazard. However, it is not recommended to drive extensively with any check engine light illuminated. Here are some precautions if P1486 is present:

  1. Drive shorter distances and avoid high loads until the issue is diagnosed. Extended drives can lead to overheating.
  2. Monitor engine temperature gauges closely for any signs of overheating.
  3. Have the code diagnosed and repaired promptly to avoid potential engine damage.
  4. The ECM is designed to operate in a backup mode if P1486 is present, but optimal engine operation may be affected.
  5. P1486 must be repaired to pass annual emissions testing in most regions.

While not unsafe to drive, it is best to limit mileage with P1486 and have your Honda Accord serviced soon. Attempting to clear the code without addressing the root cause will only result in the light returning.

Diagnosing And Fixing P1486 On A Honda Accord

Based on my experience as a master technician, here are the proper diagnostic process and repair steps for the P1486 Honda Accord:

  1. Scan for Codes
  2. Inspect Coolant Level
  3. Test Cooling System Pressure
  4. Check Thermostat Function
  5. Replace Thermostat
  6. Clear Codes, Retest
Diagnosing And Fixing P1486 On A Honda Accord
Diagnosing And Fixing P1486 On A Honda Accord

Scan for Codes

Connect a scan tool and read all stored trouble codes. Take note of any other codes in addition to P1486. They may point to related issues.

Inspect Coolant Level

With the engine cold, check the radiator and reservoir coolant level and top off if needed. Low coolant can allow overcooling and trigger P1486.

Test Cooling System Pressure

Use a cooling system pressure tester to check for leaks. Pressurize the system and inspect all components for leaks that may contribute to code P1486.

Check Thermostat Function

Start the engine and monitor the coolant temperature with a scan tool. If it fails to reach normal operating temp after warming up, the thermostat is likely stuck open.

Replace Thermostat

If tests point to a faulty thermostat, replace it following the steps above to access and remove it. Use a new OEM thermostat and gasket/seal. Refill the cooling system properly.

Clear Codes, Retest

With the thermostat replaced, clear P1486 and all other codes from the ECM. Road test the vehicle and recheck for trouble codes. P1486 should be resolved if the thermostat was the issue. If not, further diagnosis of the ECT sensor or ECM may be required.


When the P1486 trouble code appears on your Honda Accord, it can be perplexing. However, as a seasoned technician, I’ve narrowed it down to a few common causes, with the thermostat being the most likely culprit. Follow my diagnostic steps above to determine the root cause of your vehicle’s problem. Replacing a faulty thermostat and refilling the cooling system is the most common repair required to permanently remove that pesky P1486.

Frequently Asked Questions

What Is The Labor Cost To Replace The Thermostat On A Honda Accord?

For just the thermostat replacement, plan on 1-2 hours of labor at the shop rate, typically between $80-$150 total. Additional costs may apply if extensive coolant draining or refilling is needed.

Can I Drive A Long Distance With the P1486 Code Showing?

It’s not recommended. P1486 indicates the engine may have trouble maintaining proper temperature, leading to overheating risk on long drives. Have the vehicle repaired first before any long trip.

Does P1486 Cause Engine Damage If Ignored?

Letting it go for too long can potentially lead to overheating damage in some cases. However, the ECM is designed to operate safely even with P1486 active. Have it diagnosed and fixed promptly to avoid any risk.

Can P1486 Appear Randomly Or Intermittently On A Honda Accord?

It’s unlikely to be totally random. But a thermostat beginning to fail can sometimes stick open only occasionally, causing the code to come and go. Consistent occurrence points to a confirmed fault.

What If Replacing The Thermostat Doesn’t Fix P1486 On My Accord?

In rare instances, the ECT sensor or a wiring fault can cause P1486 even with a working thermostat. Checking and replacing the sensor may be required. For no other faults, the ECM may need reprogramming or replacement per Honda TSB 01-022.

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Ammar Masoud

I have had a long and fulfilling career in the automotive industry, primarily with Honda and Acura. With 15 years of experience as a Honda service technician, I became highly skilled in repair and maintenance, gaining a deep understanding of these vehicles. After many years in the automotive field, I decided to embark on a second career in industrial manufacturing. It was a significant change, but I found that the skills I had honed in the automotive industry were incredibly valuable in my new role. In my current position in industrial manufacturing, the demand for quality workmanship and meticulous attention to detail is paramount. Fortunately, these are traits that I have cultivated throughout my years in the automotive industry. I take pride in applying these skills to meet the high standards expected in the manufacturing sector.