Trouble understanding the resistor mod (MY05 WRX)

dcostzwrx · 04-07-2025, 04:20 PM

So, i'm going to be installing an aftermarket up-pipe in my WRX soon. I've been reading that you'll need to add a 2.2k ohm/.5 watt resistor to the EGT sensor plug in order to avoid a CEL relating to the EGT sensor. What i'm failing to understand, and maybe i'm just dumb.. but if the OEM EGT sensor has a resistor in it and is unplugged, then how does the ECU receive any data from it? Also, the up-pipe i'm looking at does not have a bung for the EGT sensor. So it sounds to me like EGT plug and sensor are both going to be disconnected, so it's just loose in the engine bay... do you put the resistor in the plug, then you're still able to reconnect it to the harness? First post on here so, sorry it's a dumb one, but just can't wrap my head around this mod

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benflynn · 04-07-2025, 05:05 PM

You buy a resistor, plug the legs into the unplugged egt harness. It no longer reads anything but what ever it sees with that resistor installed. The sensor is just plugging the hole at that poimt

dcostzwrx · 04-07-2025, 05:09 PM

Quote:

Originally Posted by benflynn

You buy a resistor, plug the legs into the unplugged egt harness. It no longer reads anything but what ever it sees with that resistor installed. The sensor is just plugging the hole at that poimt

holy **** i get it now and i feel like an idiot... the resistor goes into the HARNESS.. not the plug that's attached to the sensor. so i could just put the sensor in the bung and snip the wire if i wanted to? since i don't need to connect it to anything

benflynn · 04-07-2025, 10:42 PM

Correct, some worry the sensor can come apart and go through turbo, but I have seen 300k mile egt sensors no issues so I wouldn’t sweat it.

04-07-2025, 04:20 PM	#1
dcostzwrx Scooby Newbie Member#: 492479 Join Date: Oct 2018	Trouble understanding the resistor mod (MY05 WRX) So, i'm going to be installing an aftermarket up-pipe in my WRX soon. I've been reading that you'll need to add a 2.2k ohm/.5 watt resistor to the EGT sensor plug in order to avoid a CEL relating to the EGT sensor. What i'm failing to understand, and maybe i'm just dumb.. but if the OEM EGT sensor has a resistor in it and is unplugged, then how does the ECU receive any data from it? Also, the up-pipe i'm looking at does not have a bung for the EGT sensor. So it sounds to me like EGT plug and sensor are both going to be disconnected, so it's just loose in the engine bay... do you put the resistor in the plug, then you're still able to reconnect it to the harness? First post on here so, sorry it's a dumb one, but just can't wrap my head around this mod * Registered users of the site do not see these ads.

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04-07-2025, 05:05 PM	#2
benflynn Scooby Specialist Member#: 515308 Join Date: Jun 2020	You buy a resistor, plug the legs into the unplugged egt harness. It no longer reads anything but what ever it sees with that resistor installed. The sensor is just plugging the hole at that poimt

04-07-2025, 10:42 PM	#4
benflynn Scooby Specialist Member#: 515308 Join Date: Jun 2020	Correct, some worry the sensor can come apart and go through turbo, but I have seen 300k mile egt sensors no issues so I wouldn’t sweat it.