7e8 and 7e9 Engine Code: A Detailed Overview

The 7e8 and 7e9 engine codes are among the complex error codes that might be shown on your OBD-II scanner.

The 7e8 engine code is often accompanied by the 7e9 error code which is used to signify an issue in the engine data stream.

A 7e8 error code signifies air pressure loss for the emission control system which can also be likened to an issue with the engine power train. The 7e9 code indicates an issue in the engine transmission.

In this article, we are going to extensively discuss the 7e8 and 7e9 engine code including its meaning, causes, and fixes.

7e8 and 7e9 Engine Code

Even though the two engine codes seem to relate to the engine control module, there is a difference between them.

The 7e8 engine code indicates a problem with the engine powertrain meanwhile the 7e9 indicates a problem with the transmission powertrain.

Let me explain…

What is Engine Code 7e8?

Error code 7e8 is a trouble diagnostic code that indicates that there’s air or fuel intake into the engine control system thereby leading to a loss of air pressure in the evaporative emission control system of your vehicle.

The engine generates its power from the internal combustion cycle in the cylinder, and the combustion chamber makes use of petrol mixtures and trapped air to generate heat and produce a spark which in turn moves the car.

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Depending on the model of your cylinder head, uncompressed air or unburnt fuel can get into the control system and reduce air pressure in the system.

Some car models such as the Chevy and GMC Sierra will also show this code if the knock sensor detects a vibration from the engine.

This error code is a minor issue and may not cause any issues for you because it’s often resolved in minutes and a bad sensor might be responsible for showing the code.

If you’re in doubt of the cause of the error code then you can employ a multiple-purpose OBD-II scanner for this purpose.

It’ll reveal the reason(s) why your check engine light is turned on and provide possible fixes for you.

What is Engine Code 7e9?

The 7e9 error code is an indication that there’s an issue with the TMS (transmission management system) and the engine might lose power soon.

Remember the 7e8 engine code is associated with air and fuel mixture getting into the combustion system, likewise, the 7e9 engine code is shown alongside to show that there is a fuel leak, overheating, or slipping in the engine.

This code is a major one and should be resolved on time because it could result in stalling, misfiring, or an unresponsive engine.

If you’re in doubt of the cause of the error code then you can employ a multiple-purpose OBD-II scanner to help check the code.

It’ll reveal the reason(s) why your check engine light is turned on (5-digit code) and provide possible fixes for you.

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7e8 Engine Code – Causes

Here are possible reasons why the 7e8 error code will be displayed on your check engine light.

  • Leaking fuel vapor lines
  • Disconnected vapor lines
  • Damaged Canister
  • Bad Canister Close Valve
  • Bad fuel tank pressure valve
  • Unplugged fuel vapor line
  • Faulty pressure control solenoid valve
  • Bad fuel pump seal
  • A Bad fuel filler pipe
  • Bad fuel filler cap

That’s it for the causes of the 7e8 engine code Chevy.

How to Fix the 7e8 Engine Code

The 7e8 error code revolves around air and fuel mixture getting into the engine control system.

Here are some DIY tips you can implement to fix the error code.

  • Get a fuel cap replacement
  • Run an EVAP leakage test on your car
  • Perform a smoke test on your EVAP system
  • Check if your fuel level is between 15% – 80%

You can now clear the codes on your OBD-II scanner and perform a new test. The codes should clear off by now.

Also, endeavor to perform an EVAP test on your car after driving for 10,000 miles to prevent poor gas mileage and the $7e8 engine code.

You can take your car to a professional mechanic if the engine code still persists after initiating any of the above fixes.

How to Fix the 7e9 Engine Code

The 7e9 code can be curbed by regular maintenance of your vehicle. Transmission issues are usually an indication that you need to change your driving habits or ensure that your car’s engine is always standard at all times.

You can always take your car to a mechanic workshop for proper servicing and maintenance.

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They’ll make use of an OBD-II scanner to scan out all the necessary troubles on the car and fix it accordingly.

Clear the scanner and see the code disappear from your check engine light.

Difference between 7e8 and 7e9 Engine Code

7e8 Engine Code

7e9 Engine Code 

Faults in the Engine Powertrain Faults in the Transmission powertrain
A minor issue A major issue
May not show any symptoms Stalling, misfiring, or unresponsive engine
Fixes are often DIY The service of a professional mechanic is needed