2020Racing Posted February 25 Report Share Posted February 25 I'm going to run a Bosch Motorsport pressure and temp sensor in the coolant crossover pipe and I would like to see if this could possibly feed the gauge through the ECU as I will be removing the OEM coolant temp sensor. Do I use the OEM harness to reference the coolant temperature and the expansion loom to reference the pressure or just use the expansion loom Quote Link to comment Share on other sites More sharing options...
Vaughan Posted February 25 Report Share Posted February 25 So you most likely won't be able to connect the bosch temperature sensor directly to the coolant gauge in the dash but you can connect a spare PWM capable Aux to the dash sensor wire and use a gp PWM table where you vary the DC with coolant temp to move the dash gauged around. I did this on my V6 swapped MR2 as I didn't have any appropriate locations for the factory dash gauge temperature sensor. Quote Link to comment Share on other sites More sharing options...
2020Racing Posted February 26 Author Report Share Posted February 26 What is a PWM AUX? So typically a two wire sensor feeds the ECM. Then the ECM feeds the dash. Can you use the channel that is used to receieve the ECT in the expansion loom to then in the ECU programing feed the output of the ECU to guage Quote Link to comment Share on other sites More sharing options...
Vaughan Posted February 26 Report Share Posted February 26 PWM stands for Pulse Width Modulation which is when the output is switched on and off at a constant frequency and you can vary how long it is on as a proportion of each pulse. Aux 1-8 are all PWM capable and have GP PWM as an option in their function lists. I've attached an example below, you will need to alter the numbers in the table to suit your dash gauge, just do it bit by bit when increasing the values as the gauge doesn't have a linear response. Quote Link to comment Share on other sites More sharing options...
2020Racing Posted February 27 Author Report Share Posted February 27 That's a great help. Will this be on the output side from the OE connector to the ECU. Quote Link to comment Share on other sites More sharing options...
Vaughan Posted February 27 Report Share Posted February 27 You'll need to look at your pinout and find one of Aux1-8 that is not being used for something you want, AC Relay on your main ECU header is the only one I can see. Quote Link to comment Share on other sites More sharing options...
2020Racing Posted February 27 Author Report Share Posted February 27 Then will i need to physically wire this in? Quote Link to comment Share on other sites More sharing options...
Vaughan Posted February 27 Report Share Posted February 27 To clarify what engine do you have and does it have a separate coolant temp sensor for the dash cluster and the ECU and if so are you removing the sensor associated with the dash cluster or the sensor wired to the ECU. I think I might have misunderstood you here somewhere and assumed you were removing the coolant gauge sensor but on re-reading I might have been misinterpreting what you were saying. Quote Link to comment Share on other sites More sharing options...
2020Racing Posted February 27 Author Report Share Posted February 27 It is an EJ207. V5-V6 Subaru G4+ I'm removing the two wire sensor in the cross over pipe and replacing with a Bosch MS pressure/temp sensor. Wanting to hopefully still use the guage as this oem sensor feeds the ECU which then feeds the guage. Quote Link to comment Share on other sites More sharing options...
Vaughan Posted February 27 Report Share Posted February 27 Googling images of the sensor shows me a lot of 3 pin ones but if yours is a 2 pin does it have another sensor like the green circled one below? Quote Link to comment Share on other sites More sharing options...
2020Racing Posted February 27 Author Report Share Posted February 27 My appologies mine is a 3 pin. It is in the other side of that pipe and does not use a gauge sensor. Quote Link to comment Share on other sites More sharing options...
Vaughan Posted February 27 Report Share Posted February 27 A 3 pin coolant temp sensor from that age of Japanese vehicle typically has one ground pin and two different temperature sensors within it, one for the dash cluster and one for the ECU. So yes if removing it you will need to wire a spare PWM capable aux from the ECU to the dash temperature wire to control the dash temp. Or alternatively fit that sensor elsewhere in addition to your new sensor. Quote Link to comment Share on other sites More sharing options...
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