Jump to content

ECU Light Fix Decat


Recommended Posts

ECU light fixes are described below to address the P0546 ECU codes.

2.2K ohm from Maplins best place less than a £1

Or you could get one of these 


This is a great way as a temporary fix. But to get the full benefits for it a Remap is the only true way. Some modern newages also seem to know when it's trying to be tricked and will still sling the ECU light on. There shouldn't be a need to reset the ECU it might take upto 8 starts to go out when the ECU has learned. 








If you're more technical minded read on. 




The Newage Subaru Impreza WRX ECU has a table of all DTCs (fault codes) by their numeric value. If you replace one of these with a different numeric value, the code is effectively turned off. This article assumes you are familiar with reading and reflashing ECUs and have already downloaded your ECU image.
Perhaps you are looking to defeat the annoying CEL codes after installing an Up-Pipe or Downpipe. If so these are the typical CEL codes you’ll be interested in disabling:
P0037 - Rear O2 Sensor Heater Control Circuit Low
P0038 - Rear O2 Sensor Heater Control Circuit High
P0137 - Rear O2 Sensor Low Voltage
P0138 - Rear O2 Sensor High Voltage
P0139 - Rear O2 Sensor Circuit Slow Response
P0420 - Catalyst System Efficiency Below Threshold
P0545 - Exhaust Gas Temperature Sensor Circuit Low
P0546 - Exhaust Gas Temperature Sensor Circuit High
P1301 - Misfire Detected (High Temperature Exhaust Gas)
P1312 - Exhaust Gas Temperature Sensor Malfunction
P1544 - Exhaust Gas Temperature Too High
The recommended way to disable your CEL codes is to use the OpenSource tool called RomRaider. This is described below. Additionally, if your ECU is not yet supported by RomRaider (if not please let them know!) there are also notes on how to do this manually using the HEX Editor function within the Shareware program called EcuEdit



ECUEdit is a tool which can take a ECU image and visualise the maps graphically and allow user edits (remaps). Maps are described via one or more configuration files.




Disabling CEL codes in RomRaider is easy. Open your ROM in RomRaider. With reference to the illustration below, select Diagnostic Trouble Codes from the tree view on left. Within that you’ll find a (large) list of CEL codes.
To disable a CEL code, simply click on a CEL code from the tree e.g. P0420 - Catalyst System Efficiency Below Threshold and you’ll be presented with an editor. The guys at RomRaider have made this real easy, so all you need to do is uncheck the box to disable it.


CEL fix made easy using RomRaider


Save your ROM from within RomRaider and now you’re ready to upload your ROM back to your ECU.
CEL fix using EcuEdit

If your ECU ROM is not supported by RomRaider (described above) then the following, more advanced, procedure may be used to disable CEL codes.


Identifying CEL codes within ROM

Figure 1 below, illustrates a section of the fault code table from an ECU image dump of a MY03 Impreza 2.0 WRX



In the above figure we are only interested in rows with either 03, 04 or 05 in column zero. Starting from the highlighted row 24D0D, column zero indicates if this is a generic OBDII or a Subaru specific fault code (03 or 04 respectively). Column 1 and 2 is the fault code in Binary Coded Decimal (BCD) format. In this example we are looking at fault code P0420 – Catalyst System Efficiency Below Threshold. The next row 24D11 is fault code P0442 – EVAP Control System Leak Detected (Small Leak).
Disable a fault code

In the above figure you will see a number of rows with the values ’05 00 00’. This appears to be Subaru’s way of allowing fault codes to be ignored. To disable a fault code simply replace it with ’05 00 00’ e.g. for P0420 replace ’03 04 20’ with ’05 00 00’. This change has been applied in Figure 2 below. Now the ECU won’t raise a CEL for that.




Information Source: OpenECU.org, thanks to Colby and the OpenECU community for making this possible.
Disabling other fault codes

If you want to disable other DTCs follow Steps 1–2 with one minor change. When you search in Hex Viewer, leave the max count at ‘4′. Put the DTC value you want to disable in the 01 and 02 spot but try two searches. One which has ‘03′ as the value for 00, and one which has ‘04′.



If you try this it's at your own risk, if you don't know how to use it you will need to research more on Google. You must remember you are playing around with the ECU. Myself I would use a qualified mapper.

Link to comment
Share on other sites

  • 4 months later...

Sorry mate I didn't have any notification that you'd replied. Ssm subaru select monitor it's what all the dealers use you can do loads of stuff with it. I had a brief read through it and downloaded the software but cant use it. I think you can do pretty much everything with it. If you know what your doing I'll post link up. If you want I'll post you the cable ?

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...