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

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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! 

11 thoughts on “Engine code $7E8, $7E9, $7Ex – They’re not what you think they are”

  1. I have a 2015 Chevy Traverse that I bought new in 2015. I’ve never had major engine problems with this vehicle before. When I perform a scan I get:
    P0171 System Too Lean Bank
    P0174 “” 2
    P0496 Evaporative Emission System
    High Purge Flow
    $7EA: No codes

    1. P0496 causes both of the code P0171 and P0174 (lean condition, which means too much air, not enough fuel)
      You can try:
      – Tighten the fuel cap
      – Clean or replace the purge solenoid valve
      – Repair or replace the fuel tank pressure sensor

  2. First of all; thank you for being so helpful!!!
    I have a 2009 Silverado 1500 – 6 cyl that my reader shows as having diagnostic code P0700 – sub code $07e8, and sub #2 is – $07e8pd.
    The diagnostic reader says it’s a transmission code.
    After more research I have found that it “could” be a faulty Volume/Mass air flow sensor, which is very easy to replace. That said, it seems like there are a number of things that could be causing the code.
    Any advice you could offer me would be greatly appreciated.
    Thanks so much,
    Stu Neyland

    1. First, I can’t think of any reasons why a faulty maf sensor can cause the code P0700. Usually, it will throw the codes P0101.
      Secondly, common causes for P0700 are faulty transmission control module, transmission valve body fault, shift solenoid issues, or open or short in the wiring harness.
      Hope it helps

  3. A few times my 2011 volvo V50 D4 has entered slow mode with ‘engine system service required’
    This is very sporadic and limp mode deactivates after switch off (service warning goes away after a few starts) car runs smoothly all other times.

    I checked for code with a cheap obd2 and P0000 $07e8 pd Manufacturer control appeared.

    Previous to all of this a low oil message appeared and i topped up 600ml, last garage full service/oil change was 12000 miles ago.

    Any comments much appreciated.

    1. Hi, the code P0000 is quite rare and it means no fault code.
      Bad news for you, the limp mode and the CEL can mean that there is something wrong with the communication between the engine and the transmission.
      And you are using a cheap scan tool, which can’t read these kinds of fault codes.

  4. Thank you for your reply.

    This is a six speed manual gearbox and the code has appeared a couple of times on mild acceleration or sitting at 70mph on a motorway on cruise, and once during hard acceleration.

    You are correct about the scan tool, it is a cheap one that i have borrowed.

    Would you suggest a trip to Volvo/vida at this time ?

    One other thing, i always fill the car to the max and refill on about a gallon left (500/600 miles). The code never appeared on the last fill but almost immediately did it after yesterdays fill. I have read about a filler cap issue, or should i dismiss that ??

    Thanks again.

    1. If that’s the cap issue, there should be fault codes indicating a lean condition. But you don’t have them, so I would say that is very likely to be irrelevant.

      And yes, a trip to your mechanic is the way to go in this case as I highly doubt that your car has problems with the communication protocol, which is fairly complicated to fix.

      1. Thanks again for your reply.

        I havent managed to get it on a proper tester yet, though it has not faulted again in the last 350 miles.

        I shall keep you posted when i find out the cause of this.

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