Help clearing codes

Just replaced my AutoZone MAF Sensor that was causing the p0171 and p0174 codes with an OEM Denso MAF Sensor. All the places I went to either wanted to charge me money or straight up said they couldn't clear the code for me. They told me to take off the neg terminal for 10 min. Will this harm my ECU? If so, how would I be able to clear it?

 

No, it will not harm the ECU.

 

OK, thanks

 

Why would it hurt the ECU to disconnect the battery? There is a very likely chance at some point the battery would die and you would have to disconnect the battery anyway to replace it, they wouldn't do that to someone.

 

You can get a very good OBDII reader on eBay for $50-60. You can even get the bare bones POS one for $30 that will allow you to read codes/erase them. Go with one of those options instead of blindly pulling the battery cable.

Actron has numerous options for under $100.

 

I got a little cheap one to read codes. Don't think I can erase them though. I disconnected the battery and reconnected and the light went away. Haven't driven it since I did that so I hope the light doesn't come back because if it does, the Toyota mechanic told me it could be my cat going bad. Idk if that's true or not, just repeating what he told me

 

ha that tech nees a refresher on engine performance if he thinks the cat will cause lean codes lol

 

Lol well he told me that the engine was running too rich and too poor. He then proceeded to tell me that one of two things could be wrong. The MAF which I already knew, or the cat. I don't know much about cats but wouldn't there be a much bigger difference in performance if it was going bad?

 

under extreme cirucmstances yes it could cause performance issues, but theres about a 2% chance that the cat is causing the p0171 code. ur looking at more of a maf, vacuum, leak, lack of fuel pressure, exhaust leak before sensor 1

 

Well, I'll keep an eye on the CEL tomorrow going to and from work and see if it comes back on. If it does, what would be the next thing to check?

 

it takes 2 failures for the ecu to turn the light on, could take a few drives if its gonna happen. hard to diagnose a lean code without a scan tool man... need to beable to see what sensors are doing and when/ what circumstances they do it.

 

I have one, just not a higher grade one. It runs through an app on Android called Torque and connects to my phone via Bluetooth. I only have the free version. Idk what the paid version allows you to do. But that's a long term investment for me. Money is just real tight.

 

Something causes the cats to go bad, they typically don't fail on their own. If it is the cat then there is probably some underlying issue. Have you changed the AF sensor and O2 sensor?

Ask the mechanic what is causing your truck to run too lean?

Hopefully it was the MAF and your problem is solved

 

I'm presuming you're asking about the sensor I talked about in the OP. If not, idk which sensor that is. And no clue on the O2 sensor. Truck was pretty neglected when I got it. So I highly doubt its been changed.

 

this^ ask the mechanic why its running lean

 

The MAF and the cat are the two things he said could be wrong. I didn't get them to fully diagnose it because that would have been hundreds of dollars.

 

The MAF could cause the truck to run lean which hopefully has been solved. But if he blames the cat converter then ask "what caused the cat to go bad?"

 

CEL came back on no more than 2 min of turning on my truck. Hooked up my scanner. Read p1135 code. What does that mean?

 

It means your upstream O2 sensor is not reporting the air/fuel mix after the manifold and before the cat to your ECU.

In other words, you probably have a bad upstream O2 sensor.

This can also cause a lean condition, because the ECU is confused as to how much fuel to give the motor because it doesn't know how much is burning due to not having that reading. This could also explain a P0420 error.

 

I believe my previous codes were p0171 and p0174. How difficult is it to replace the upstream o2 sensor?