Saving Silverado (Part 6): Replacing the Knock Sensor on LS-Powered GM Trucks

Jumping onto the Summitracing.com website, we were able to order everything we needed to complete the job. From the tools to the replacement parts, Summit had many options for us to choose from.

After plugging in the Actron Elite Auto Scanner, we simply needed to follow the prompts, starting with the make and model of vehicle.

The eighth digit in the VIN gave us the correct engine code.

Getting to the heart of the problem, we scrolled to diagnostic codes.

The display shows our knock sensor error code, P0332.

As the air intake tube had already been removed due to the water pump installation, it was straight to the beauty cover with the socket.

An 8mm socket allowed removal of the beauty cover.

Underneath the cover is this attachment plate. There are three fasteners; the one at the back will require a wrench as there is not enough room to get a socket and ratchet in there.

Now it’s time to start disconnecting everything, starting with this vent right behind the throttle body. This truck, being a drive-by-wire model, thus does not require removal of the throttle cables.

Unbolt this purge valve next—you’ll need to snake it and the plastic line attached to it, out from under the fuel rail.

Remove this fastener holding the main wiring harness to the intake.

Taking a break, it’s time to depressurize the fuel system. Remove the cap, cover the orifice with a rag, and gently release the pressure by using a screwdriver or other implement to depress the valve. There shouldn’t be too much that comes out, and waiting to do this after the engine has had time to cool down will help.

Disconnecting the fuel injectors is a bit tricky, as you need to depress this safety clip and remove it before you can unplug the injector.

The alternator connector needs to be unplugged as well.

At the throttle body, there are two plugs on the right side and the throttle control here on the left. You need to lift on the small black part to remove the gray piece, and then you can unplug the large black plug from the throttle body.

On top of the intake manifold and towards the rear is the knock sensor harness. Unplug it and unclip it from the manifold, as you’ll be replacing this.

We did find one guy that was able to remove the throttle body without disconnecting these coolant lines, but since this cooling system was empty from the water pump change already, we opted to remove the lines to make things easier.

Remove this vacuum line from the right side of the intake manifold.

Next, disconnect the vacuum line to the brake booster.

Disconnection of the fuel line is next. First, remove the safety clip.

We were lucky in that the first tool we tried on the fuel line popped it right off. The handle on this particular tool gave us some much-needed leverage.

Three nuts and the throttlebody came right off. Take care not to damage the gasket.

The last thing that should hold you up is this plug at the very back of the intake manifold. Just disconnect it and be sure you don’t forget it upon reassembly.

Carefully lift straight up on the intake and then begin to pull it forward while lifting the front of it up. It may catch on things here and there, so having an extra set of hands and eyes comes in handy at this point.

As you can see, it is trash city down here with the intake manifold off. Not having vacuumed prior to the manifold removal allowed some debris to fall into the intake ports. Be sure to remove any debris prior to reinstalling the intake.

It would seem that more than just the knock sensors met an untimely demise in this environment. When you go to pry up on the plug, you’ll notice how hard the rubber has become, and it may even swivel or wobble in the hole, which indicates it is no longer sealing properly. Once the plug is up, the harness may disconnect itself, but if it doesn’t, just squeeze it until it comes loose.

Here is the rear sensor, and as you can see, it has seen better days.

The front sensor faired much better, but we’re not leaving anything to change. A 22mm socket is needed to remove the sensors. The new sensors (PN DFP-AS10017) are to be torqued to 15 ft-lbs, but many torque wrenches start at twenty. You can wing it and hope twenty is accurate and sufficient, or see it as an opportunity to add another tool to the chest and pick up an inch-pounds torque wrench. 15 ft-lbs equals 180 in-lbs. Attach the new harness (PN RNB-917-033) and route it out the back of the lifter valley.

Per GM’s recommendation, apply a bead of RTV sealant around the front half of the knock sensor plug. Some choose to completely seal it, but we imagine there is a reason for GM’s specification.

The new intake gaskets simply clip onto the manifold so you don’t have to worry about sticking them to the cylinder heads with RTV before you drop the manifold on. This design makes for an easy clean up upon removal, which we performed but opted not to show. The torque sequence for tightening the manifold bolts is as follows—44 in-lbs on the first pass and 89 in-lbs on the second. Reverse the disassembly steps carefully and you should be good.

As we had erased the code after reading it, upon start up, we were greeted with a CEL-free instrument panel.