brama Posted January 10, 2007 Share Posted January 10, 2007 I have a 91 Legacy 2.2 auto awd ecu is a H5. I also have a parts car 92 Legacy 2.2 auto awd ecu is a H9.The difference between the 2 cars is that the parts car has ABS and cruise. Can I swap the H9 for the H5. The reason for doing this is that I think the H5 ecu is corrupt. I am having problems with the cooling fans not working and the temp gauge goes to the top once the ignition is turned on( car not running). I have changed relays,temp sensor,thermo sensor also have disconected battery overnight to reset ECU. I have also checked for shorts. So this leaves me with only one thing, ECU. Thank You Quote Link to comment Share on other sites More sharing options...
nipper Posted January 10, 2007 Share Posted January 10, 2007 WOOOOOOOOOOOOoooooo the temp sesnor if i remember correctly is not in the ecu circuit (gauge temp). What you have is a short or a ground someplace. Radiator fans are controled by the ECU, but the AC will over ride them. You have a wiring problem someplace and not an ECU issue. The temp gauge itself has absoloutly nothing to do with the ecu. If you have a wiring problem, and it did damage the ecu (very long shot) by not finding it you can damage the 2nd ecu. My guess is that you have a bad ground (gauges ground through the sensor) or a short going to ground. Its possible that the fan ecu signal is in the related harness. nipper Quote Link to comment Share on other sites More sharing options...
brama Posted January 10, 2007 Author Share Posted January 10, 2007 I have a wiring diagram for 92. Temp sensor is a single wht/grn wire that runs to temp gauge. The coolant temp sensor has two wires blk/yel and grn/blk. The grn/blk wire switchs to a red/green that goes to the ecu. But also tees off and runs to the temp gauge,connection A pin 8. I have tested the circuit and it seems the the ECU is not sending a signal to the relay for the fan. So I am thinking the somehow I do have a short in the Ecu. When I unplug the temp sensor (wht/grn wire) the temp gauge goes back to Cold. That why I what to swap the H9 for the H5 if it can be done. Quote Link to comment Share on other sites More sharing options...
nipper Posted January 10, 2007 Share Posted January 10, 2007 Odd my haynes manual has the gauge as a stand alone sensor, single wire, that goes to ground. Before you go through all that, take an ohm meter to the two ends of the wire and see if there is a short or an open. Its possible the ecu is bad, but check the wires first. nipper Quote Link to comment Share on other sites More sharing options...
brama Posted January 10, 2007 Author Share Posted January 10, 2007 I am going to go over my wiring again. The wiring diagram is from Legacy777 website. But what I need to know is that if all else falls can I swap ecu's. Quote Link to comment Share on other sites More sharing options...
nipper Posted January 10, 2007 Share Posted January 10, 2007 I am going to go over my wiring again. The wiring diagram is from Legacy777 website. But what I need to know is that if all else falls can I swap ecu's. look at the amount of pins, if they have the same amount of pins i dont see why not nipper Quote Link to comment Share on other sites More sharing options...
johnceggleston Posted January 10, 2007 Share Posted January 10, 2007 look at the amount of pins, if they have the same amount of pins i dont see why not nipper i'm pretty sure i know the answer to this but with only a few years of subaru experience i'll ask any way. when i swapped the 96 leg 4eat into the 95 leg i didn't swap the TCU, amy chance this is causing my TB on the 96 trans. or more importantly, whe ni make the repair, will it do it again? everything worked great for 3000 miles now duty c and TB. like i said i think i know the answer. Quote Link to comment Share on other sites More sharing options...
Legacy777 Posted January 11, 2007 Share Posted January 11, 2007 The ecu's are swappable, however the 92 ECU has the MT/AT identifier pin wired backwards, and the injectors are different which will cause the car to run rich. You can swap the 92 ECU in, and at least see if that fixes your problem. However I'd recommend you use a 90-91 ECU. Quote Link to comment Share on other sites More sharing options...
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