ECU or O2

Hi All,

I have a base model (wind windows no cruise) 2008 extended cab tacoma with 4cyl engine and the 5 speed box.

My issue is with a Check Engine fault.
When I read the codes it says that the heater circuit on the O2 is faulty.
I obviously replaced the O2 (UP and Down) but the issue persists.
My local garage (general repairs not Stealership) says I need a new ECU.
I got them to test the wiring to see if there was a signal at the connector and there is.

So.....
1) Is there any other testing that I can do before going to Toyota.
2) If I replace the ECU I assume it needs to be VIN programmed.
3) Also are they VIN locked once done or can I get a 2nd hand one and reprogram.

Also would TECHSTREAM give me a better answer than "probably the computer", I see there is an Air/Fuel module under the hood as well

Thanks in advance for any and all help

 

I've seen ECU's cause this, recently no less. It's a nightmare.

ECU's arent vin locked, they just need the vin to be programmed with a scan tool or it will show mismatch.

 

So can you buy a 2nd hand one and change the vin?

 

Te hdtream os just going to show you what the ECM sees.

Did they test resistance in the harness? Just because there’s signal doesn’t mean it’s working properly. If there is corrosion, bad pin retention, or a broken wire, you can see the signal but what the ECU reads or is able to provide through said wiring can cause it to think the sensor is bad.

If you can get an ecu cheap or borrow one, that’s an easy way to see if the code persists. Especially if you can swap yours into another truck. See if code follows truck or ECM. but if I didn’t want to buy a new ECM I’d test the wires or string some new wires and see what happens first.

 

So a 2nd hand ecu would work without coding? would it have to be a base truck like mine or is just 4wd 2.7l 5speed ecu I need?

Not sure how to test the wires, or run new ones. Do you know if there is info on this somewhere that I can follow?

 

Easy to test the wiring, Heater Power can be checked at the sensor connector with a test light connected to a known good Ground. The light should light up when connected to Heater Power with the key on, This would be Pin 2 (White) at the Upstream AFR Sensor and Pin 2 (Blue/White) at the Downstream O2 Sensor.

Also need to check wiring integrity of the Heater Control wires to the ECM as well as check the resistance of the AFR and O2 Sensor heaters themselves.
If it does need an ECM your fine going used, they are plug and play on US 4 cyl trucks. You just need to match the part number of the ECM and the VIN in the ECM should be changed to match the truck but this step isn't necessary for it to run, it will be a requirement if you are in an emissions testing area because the ECM VIN must match the truck in order to pass. Most mid to high end aftermarket bi-directional scan tools can perform a VIN Write.

AFR Sensor




O2 Sensor

 

If these tests seem out of your wheelhouse and you can find a used ECM cheap, then it may be worth swapping and testing. You can always throw it on eBay and get a couple bucks back if it’s not the ECM.

But if you swap the ECM and the problem stays, you’re going to have to diagnose the wiring.

Dealers choice which you want to start on. I’m not saying ECMs don’t fail, it’s just more common for wiring to get pinched, corroded, or connectors to lose pin retention.

im sure your shop is reputable, but most techs won’t take the time to really diagnose the wiring and connectors to the point of checking resistance. It’s easier and pays better to swap the ECM and go from there. I mean no offense to that. This is coming from 15+ years of working with dealer techs to troubleshoot challenging diagnostics. They often have the advantage of having spare parts laying around or trucks in the lot they can borrow them from for testing.

 

thanks for the info everyone. I will see what I can get done. again thanks