The truck is a 2000 Silverado 1500 Z-71 that I've owned since new. I had done the knock sensors back in 2006 when the rig had just under 100K on the clock. That said it lasted 14 years without a single code. The truck now has 245,xxx on the clock and over 7K hours. Well after my latest engine wash down and chassis clean out the truck threw a "Sevice Engine Soon" a couple of days later. My scan tool indicated a PO332 indicating Knock Sensor 2 (rear). Many of you know these knock sensors live under the intake manifold on these early model ls engines. A crappy design that likes to trap water in the deep wells to the Valley top plate.
The fault code.
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Although the rig was running just fine it wouldn't pass emissions testing with the "Service Engine Soon" light on.
These early sensors are a single wire with the ground being the block boss where it mounts. A quick meter check confirmed the dead #2 sensor.
Removing the entire intake manifold and disconnecting the fuel injector connectors, I was bound to break something made of plastic with it being 21 years old and exposed to heat. I was actually force to break #5 FI connector as the stupid secondary clip had snapped inside the connector preventing the squeeze tab from being pushed in. A flat head screw driver was inserted and a lite twist popped the connector off by splitting it. All other connectors came off without any drama.
With the intake off you can see my previous work indicated by the hi temp RTV around the harness boots.
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The Valley top cover was never removed the first time around as the truck was only 6 years old at the time. The original harness was also reused at that time. The RTV was an attempt to keep water out but with the grommets now being 21 years old they had become brittle and shrank, breaking the RTV seal.
Back in 2006, there were no real aftermarket intake gaskets available for this so I used OEM plastic snap on (to intake) gaskets sourced at the dealer. I also used AC/Delco knock sensors as I didn't have confidence in aftermarket sensors given the amount of work needed to access them.
This time around Fel-Pro offers a very nice intake gasket kit that included aluminum based with thicker impregnated seals as well as a throttle body seal, fuel injector O-rings and EGR seals and gasket for $7.00 over the OEM intake gaskets. I also purchased a new AC/Delco harness and two new AC/Delco knock sensors, AC/Delco FI connector pig tail, coolant crossover tube seals and a Fel-Pro top Valley cover gasket kit that also includes two rubber bushings that seal around the Valley bosses where the sensor screws into. Since I was staring at the oil sending unit, I purchased a GM brand unit. Aftermarket sending units will cause the oil gauge to flicker at idle so don't use them. Aftermarket knock sensors are. not calibrated to the same frequency for the ECU to read properly so don't use aftermarket knock sensors either.
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Here you can see the rear knock sensor rusted from water intrusion.
![Image]()
With the Valley cover removed and the gasket surfaces prepped for reinstall I pulled out the old hard and deformed 21 year old bushings and put the new one in.
Important note: These bushings are the only thing keeping water out of the engine. There are openings with a direct view of the cam at either ends of the valley. The one that is damaged was a result of the top plate being removed where it seals around the threaded boss inside the Valley.
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New bushings installed.
![Image]()
You can see the two threaded bosses in the block Valley where the sensors thread into.
On a side note: No sludge inside this engine with 245,xxx miles. Mobile 1 every time it's serviced.
![Image]()
With the top plate installed and torqued to 15ft/lb and in a criss cross pattern indicated by the sharpie. Medium strength thread locker is on these bolts. The four ear plugs are sealing off the water journals where the crossover tubes mount.
Everything was vacuumed prior to final assembly.
![Image]()
Next up, the new knock sensors were installed, new wiring harness and resealed the new grommets along with the installation of the crossover tube. The new harness was secured in two locations using zip-ties to the crossover tube to prevent any chaffing. Here you can also view the upgraded Fel-Pro thicker intake gaskets that snap on over two head bolt heads keeping things indexed.
![Image]()
The intake was stripped from the throttle body, MAP sensor, evaporation sensor, and fuel rail/injectors for a thorough cleaning.
![Image]()
Ten photo limit.....
More to come.....
The fault code.
Although the rig was running just fine it wouldn't pass emissions testing with the "Service Engine Soon" light on.
These early sensors are a single wire with the ground being the block boss where it mounts. A quick meter check confirmed the dead #2 sensor.
Removing the entire intake manifold and disconnecting the fuel injector connectors, I was bound to break something made of plastic with it being 21 years old and exposed to heat. I was actually force to break #5 FI connector as the stupid secondary clip had snapped inside the connector preventing the squeeze tab from being pushed in. A flat head screw driver was inserted and a lite twist popped the connector off by splitting it. All other connectors came off without any drama.
With the intake off you can see my previous work indicated by the hi temp RTV around the harness boots.
The Valley top cover was never removed the first time around as the truck was only 6 years old at the time. The original harness was also reused at that time. The RTV was an attempt to keep water out but with the grommets now being 21 years old they had become brittle and shrank, breaking the RTV seal.
Back in 2006, there were no real aftermarket intake gaskets available for this so I used OEM plastic snap on (to intake) gaskets sourced at the dealer. I also used AC/Delco knock sensors as I didn't have confidence in aftermarket sensors given the amount of work needed to access them.
This time around Fel-Pro offers a very nice intake gasket kit that included aluminum based with thicker impregnated seals as well as a throttle body seal, fuel injector O-rings and EGR seals and gasket for $7.00 over the OEM intake gaskets. I also purchased a new AC/Delco harness and two new AC/Delco knock sensors, AC/Delco FI connector pig tail, coolant crossover tube seals and a Fel-Pro top Valley cover gasket kit that also includes two rubber bushings that seal around the Valley bosses where the sensor screws into. Since I was staring at the oil sending unit, I purchased a GM brand unit. Aftermarket sending units will cause the oil gauge to flicker at idle so don't use them. Aftermarket knock sensors are. not calibrated to the same frequency for the ECU to read properly so don't use aftermarket knock sensors either.
Here you can see the rear knock sensor rusted from water intrusion.
With the Valley cover removed and the gasket surfaces prepped for reinstall I pulled out the old hard and deformed 21 year old bushings and put the new one in.
Important note: These bushings are the only thing keeping water out of the engine. There are openings with a direct view of the cam at either ends of the valley. The one that is damaged was a result of the top plate being removed where it seals around the threaded boss inside the Valley.
New bushings installed.
You can see the two threaded bosses in the block Valley where the sensors thread into.
On a side note: No sludge inside this engine with 245,xxx miles. Mobile 1 every time it's serviced.
With the top plate installed and torqued to 15ft/lb and in a criss cross pattern indicated by the sharpie. Medium strength thread locker is on these bolts. The four ear plugs are sealing off the water journals where the crossover tubes mount.
Everything was vacuumed prior to final assembly.
Next up, the new knock sensors were installed, new wiring harness and resealed the new grommets along with the installation of the crossover tube. The new harness was secured in two locations using zip-ties to the crossover tube to prevent any chaffing. Here you can also view the upgraded Fel-Pro thicker intake gaskets that snap on over two head bolt heads keeping things indexed.
The intake was stripped from the throttle body, MAP sensor, evaporation sensor, and fuel rail/injectors for a thorough cleaning.
Ten photo limit.....
More to come.....
