Repeating p0038 after cat theft. Ecu?

P0038 indicates too much current flows when the ECM wants to run the sensor heater. A zero-ohm sensor heater would definitely do that. 11 to 16 Ω at 20 ℃ is the spec.

Where are you measuring the resistance? Right at the sensor itself? While it's unplugged? That would have to be a bad sensor, kinda weird.

The other possibility would be a short in the wiring left by the scum who cut it to steal the cat. But in that case you'd see the 0Ω when measuring the harness, or backprobing the sensor while plugged in.

It would be possible for a short to damage the ECM so you'd need to replace that, but I wouldn't jump to that conclusion unless you rule out shorted wiring and get a sensor with an 11 to 16 Ω at 20 ℃ heater and still get the code even then.

A replacement ECM shouldn't really need any programming. You might want to check what calibration (firmware) ID is installed in the one you've got, and compare in the replacement (especially if bought used) just to make sure the replacement isn't missing any updates that had been applied to the original.

 

Usually I get this code that mention something about the O2 sensor heater when I'm working on cars that have had the catalytic converter stolen and the wires are still cut right there where they took the converter out and they're laying literally on a part of the car like draped over a pie for they're just sitting there I'm working on two cars right now that have both have their converter stolen The people want to get the car running they got codes all over the place and one of the main codes they have is the code for the oxygen sensor the lower one heater circuit something I don't remember exactly what it says I can go look and type it all out but I don't think it's necessary and then I look down and I see the wires are cut this is at a place with a whole bunch of wrecked Prius so I told the guy go get that plug and what's cut on this car from that car over there then we'll splice that in with the little silly splicers and will plug in an O2 sensor from that other car over there so it's a Toyota unit and we'll see then I cleared the codes and rescan the car again while it's just sitting there not on and the code is magically not there for the O2 sensor downstream heater circuit so there's always that The second car over that I'm working on with the same problem bled the brakes and did some other things got everything running it was missing on three cylinders had coils in it that look like they were blowing through the extensions the voltage and trying to ground out on the metal part of the spark plug tubes change the coils out from a car across the lot which had brand new coils in it a name I've never heard of before but they were pretty put them in car runs as smooth as a brand new one. On the second car the code is still there for the oxygen sensor. And I tell the dude we need to straighten that out and he says No I got a customer that needs his car right now will just leave it they've been driving it ever since with no problems getting 44 mi to the gallon driving like morons complete silly people flooring it from every stop light that kind of thing they're just going to leave the wires dangling I imagine.

 

I haven't worked on one of these yet where I've had to replace any electronic control modules so that's like I don't know eight cars that we've done semi-extensive work too most of them got replaced batteries and so on almost everyone got to replaced actuator for the brakes etc but we've replaced no ECMs even when we have the heater code for the O2 sensor just splicing in a plug and getting a sensor from another car and making sure that it's plugged in whether it's screwed into the exhaust system or not some of these things are just dangling because these people are putting on straight pipes and whatnot they don't even have a place for the O2 sensor to go unless they're going to eventually go back to a converter and all of that but the discussions I have with most people they're not doing anything like that so there's always that I guess and their cars are running fine getting reasonable gas mileage nothing stellar but nothing poor either kind of seemingly in the middle of the business That's why I haven't really fixed my PO420 on any of our Prius We just leave it doesn't affect gas mileage at all and we don't have to worry about it in the state that I live in The cheap converters no matter what I do with the downstream O2 sensor they don't ever seem to put that PO420 to rest so what's the point

 

Have you run your hand up under the seat and checked the plug that's under the seat just to make sure it's plugged up together or something. There's a rubber gasket usually in the floorboard I don't know if the plug is long enough to pull through the floorboard so you can look at it I would think there should be some cash that you can do on the car side of the plug with the volt and ohm meter I would think that's just really weird because we've had this p code for the heater circuit I had it twice last week and I thought that the heaters go bad in the sensors not that the ECU burns up and can't put the heating circuit on in said sensor

 

Before you did any of that, did you measure the resistance of the brand new sensor's heater? What was the reading? Better not be 0 Ω.

If the new sensor checks out with a reasonable resistance, have you double-checked that the 0 Ω you saw before could not have been a short in the wiring? If you unplug connector E6 at the ECU and then measure between the black +B and green HT terminals at the sensor connector, what is that resistance?

I would at least make that check before swapping the whole ECM.

 

If you leave the O2 sensor unplugged, clear the codes, and then ready up the car - what code sets then?

Yes, the ECM on a Gen2 is plug & play.

If you're careful, you can flip the harness around and plug in the replacement ECM for testing without mounting it.



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If you have a vehicle to swipe it from or whatever go ahead like I say you can flip the plug around and plug it up without removing the other one and see if this is the case I kind of think I don't know what to think at this point but I'm not sure what the numbers are supposed to be for the ohm test you run Chapman will know when he comes along and sees it or he has access to look it up quickly somewhere the manual is online and you can look at it as you want I just don't have the link for it there's a bunch of people here that have it and access to it or what have you