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Engine code $7E8, $7E9, $7Ex – They’re not what you think they are

Your check engine light is on, and maybe the car entered limp mode. So you bought a code reader to see what’s really going on with it. 

The device gave you the codes $7E8 and $7E9. But what issues do these codes indicate? What needs to be fixed? 

Actually, they are not engine codes. $7E8 and $7E9 are just submenus for engine and transmission control modules. 

Let’s dig deeper! 

$7E8 & $7E9 engine code – What do they mean? 

$7E8 and $7E9 engine code

Again, $7E8 & $7E9 are not engine codes. A basic OBD2 scan tool offers a few different modes (from 1 to 10) to perform particular tasks on your cars. In this case, $7 represents mode 7, which basically means diagnostic code request. 

E8 (or E9) indicates that you request fault codes from module E8 (or E9). In conclusion: 

  • $7E8: request codes from the engine module
  • $7E9: request codes from the transmission module

What you have to do when seeing these submenus is to click on them, and you’ll get the fault codes. 

For both of these modules, you’ll get powertrain codes, which are Pxxxx (e.g., P0218 or P0171).

Most common fault codes in $7E8 & $7E9

The table below is the most common fault codes that you’re more likely to have. 

Note: It’s not 100% that your car will throw these codes. However, as a mechanic, I would say 70% chance you’re going to have those. Whatever codes you receive, leave a comment below. I’ll try my best to help you all. 

$7E8 Description $7E9 Description
P0171-P0175Faulty oxygen sensorP0218Transmission over temperature
P0300-P0305Engine misfireP0613Transmission control module (TCM)
P0411, P0440, P0442, P0446, P0455Evaporative systemP0614ECM/TCM incompatible
P0401Faulty EGR valveP0700Transmission control system malfunction
P0420, P0430Bad catalytic converterP0706Transmission range sensor circuit range/performance
P0715 Input/turbine speed sensor circuit malfunction
P0720Output speed sensor circuit malfunction
P0729-P0736Gear ratio problems

What do 7EA, 7EB, 7EC, 7ED, 7EE, 7EF mean? 

Just like 7E8 and 7E9, these 7Ex submenus are not engine codes (and they are not commonly found as 7E8 and 7E9). 

7EA, 7EB, 7EC, 7ED, 7EE, 7EF refer to the communication CAN identifier. Some OBD2 code readers use these codes when it needs more info, such as which part of the ECU(engine control unit) needs to be scanned. 

  • 7EA: Physical response CAN identifier from ECU #3  
  • 7EB: Physical response CAN identifier from ECU #4  
  • 7EC: Physical response CAN identifier from ECU #5  
  • 7ED: Physical response CAN identifier from ECU #6  
  • 7EE: Physical response CAN identifier from ECU #7 
  • 7EF: Physical response CAN identifier from ECU #8  

When the tool has access to these sub-menus, click on all of them to check if there are any fault codes.


Getting to those $7Ex submenus is the very first step to know what’s wrong with your car. It’s important to go through all of the submenus you have. At the end of the day, you still want to look for all of the potential issues to turn off that annoying check engine light (or transmission light) off. 

When you receive the code, the problems may be super easy to fix; or may be very complicated. Whatever it is, don’t forget to leave a comment below. I’ll do the best I can to help! 

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