My check engine light turned on and I had the codes read at a dealer. The codes said that my front 02 sensor was bad. Replaced the sensor and reset the code. Light came back on again and now the code is saying that the sensor is over heating. The dealer is saying my ecu is bad and they want to replace it for $1200. Does this sound right?
MAF sensor was replaced also.

 

just take in a bottle of vaseline to them before they charge you for a new ecu......stupid dealers. Why is it that people dont go get 2nd or 3rd opinions? jeez.

 

get a second opinion

 

I would get a second opinion before you drop $1200. Dealerships love to "parts swap" instead of diagnose the problem correctly.

I have seen this problem before in vehicle, and the most common problem seems to be the catalytic converter. That is also an expensive option, but personally I would rather fix one spendy problem than throw $1200 uselessly at a truck and still have a problem.

In my experience working at this wrecking yard, in 9 years I have never sold an ECU for a 99 4Runner, and have zero calls.

 

if the sensor is "over heating", which i've never heard of ever before, How is it overheating? from electrical overload? or from the cat being backed up? Gotta ask why.

 

Thanks for the help! The exhaust smells like rotten eggs so I think it is the CAT. I have been searching all over the web for information on a bad ECU and can find very little resources. Truck is running fine but I need to get an emissions test for new plates here in Colorado. It won't pass with the light on. If I change the CAT what do you guys suggest for a new one?

 

I've got a magnaflow high flow cat and i passed the sniff test and my 3.4 swap isnt' throwing any codes for it.

 

This is a TELLTALE sign that the cat is bad. Check here on YT for similar stories.

 

Well... just got back from a second dealer that had a look. They were more informative regarding the issue. They tested the wiring from the 02 sensors back to the ECU as the only reason the 02 sensors would be heating up (both front and rear) and have a code is if the wires were grounding out. The wires are fine. They suspect the ECU is also the problem because it is not normal for both 02 sensors to have the same heating code. They said that each 02 is on a seperate driver on the ECU. Advice???

 

Usually when an ECU goes bad it throws lots of weird codes, so they may be right in saying it needs one.

 

If the cat is bad it "can" overheat the O2 sensors.

 

Update. Bad ECU was the problem. Not a cheap fix @ $1000.00.

 

^Eww lots of money... Glad its fixed

 

$1000?!?!

Should have called Nix99, i hear they have them for much cheaper.

 

hope this was not the same part number...could have saved a boatload of cash looking over on Marketplace

https://www.yotatech.com/forums/f109...5420-a-213196/