(Gen1) o2 sensor 1 shield cowl matters maybe

1.8-liter VVTL-i (2ZZ-GE) and VVT-i (1ZZ-FE) engine, transmission, exhaust, intake, and performance tuning discussions
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Vulcan
Posts: 64
Joined: Sat Jun 06, 2020 5:53 pm

(Gen1) o2 sensor 1 shield cowl matters maybe

Post by Vulcan »

short version: put all the parts back on the car, stupid.

In troubleshooting my 2006 AWD, I had errors on o2 sensor 1.

Turned out the Sensor was right, and replacing it only added to my confusion.

I could not get the heat shield/cowl off the first Sensor, and after asking around, decided to install the new sensor without the shield. Looks like many cars don't have cowls on their upstream o2 sensors. And obviously, there is no cowl on the downstream one.

What could go wrong?

A lot. ;)

My car was developing exhaust leaks the FIRST sensor was correctly picking up, so it wasn't until I replaced the whole exhaust system, and still had lean codes on the (new) sensor 1, that I started wondering again. What about that heat shield? It's either that, or maybe the intake is leaking. But I've checked the intake several times, haven't found a leak. Was thinking of checking it again, but why not swap the sensors again? It's too easy not to.

So I put the first sensor with the heat cowl back on, start the car - CEL immediately gone! I've taken a few short drives in the country, has stayed off (knock on wood).

My best guess is that the heat shield, with its four vent holes, protects the backside of the sensor from overheating, and its an immediate effect being right on top of the engine.

All I know is, the o2 sensor voltage error, and the lean code error, immediately went back to normal.

205k , runs great, shifts great. Suspension is pretty bad, though not failing, and rear alignment is impossible without replacing parts. I'll either rebuild all of that, or just drive it another year or so and retire it. Whole exhaust only cost me $275 because Canada rocks.
2006 AWD, 207k
jolt
Posts: 945
Joined: Sun Mar 02, 2014 2:07 am
Location: Twin Cities, Minnesota

Re: (Gen1) o2 sensor 1 shield cowl matters maybe

Post by jolt »

Just curious, was the replacement sensor a Denso or some aftermarket brand?
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