DTC Codes on my 02 Tahoe

I ran my AutoCal the other day to look up my error codes and the AC came up with 3 of them.
P0135, Upstream O2 Sensor (left cylinder bank) heater performance
P0327 Knock Sensor signal freq outside normal range
P0332 Knock Sensor signal freq outside normal range

According to the Haynes manual, the 02 sensor has a feature were it allows the sensor to heat up so it can do its thing. I think that's what wrong with mine. Being that it's the heater performance I dont belive its affecting the air fuel mixture, but I might be wrong about that. Either way I'm planning on replacing them both just to be safe. Anything I should know about doing this?

My concern is the other 2 codes. I thing my Tahoe has 2 knock sensors. I don't think the engine is knocking or doing anything weird, at least I can't hear anything obvious, so I think the actual sensors are bad.

So my question is, how difficult is getting to the sensors to replace them. The Haynes manual has me removing the intake manifold, and to be honest I'm a bit intimidated by that. Are there any considerations In should know about if I decide to do this?
Is there a gasket that needs to be replaced when removing the manifold?

Thanks
R

I had to do mine when I made the monumental mistake of hosing off the motor. Motor ran normally.

There is a small harness coming out from under the manifold near the firewall near drivers center. You can just reach the inline plug. Can't recall the number of wires (3 or 4 small wires) but if you have a meter you can measure the disconnected wires leading to the manifold. Should be 100 ohms for each sensor.

It's not too bad but some area are a pain like the injector wires and fuel fittings. As long you need to pull the manifold, anyway, get the Felpro problem saver gasket kit. A google search will get you tons of info on the gasket swap. That will get you where you need to be for the sensors. Order the gasket set, 2 sensors, 2 sensor pigtails (in case the old ones are corroded), fuel line tools, degreaser, and a bunch of silicone sealer (for the sensor mod). An inch pound torque wrench will needed when bolting the manifold back on.

Good luck

Yep unfortunately i just had to replace the intake manifold gaskets on my 02 about 2 months ago. Knock sensors are located directly under the intake manifold. So i switched them out while i had it off and replaced the gaskets.

Make sure you get the fuel line tool. Costs maybe 8 bucks, and its definitely worth it, without it you will be very unhappy!

Make sure you grab the torque specs for the intake also, there is a specific 2 pass torque sequence to follow.

mine is a 2002 5.3l gas (non flex fuel)..attached is the torque sequence.
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