We have a 2003 Chevy Tahoe with a 5.3 V8 engine. We recently got a check en gine light for a knock sensor. The message on the scanner was "Knock sensor reading low voltage". I have read about this problem a bit and it seems li ke the harness inside the engine, rather than the sensor itself usually fai ls and causes this problem.
This repair apparently involves removing the intake manifold, and this is a job we'd rather not have to do on an occasional vehicle. So I also read th at this sensor could be bypassed with a `100 ohm resistor. This would run t he car in "limp" mode. I don't really know what that is but if it is just a small loss of power I didn't think that would be a problem for something w e would just use to bomb around town in.
So we unplugged the harness from the engine and plugged a 100 ohm resistor into it. We taped it up well and pushed this wire into a tight grounded met al can. I read that the sensor, or rather I think there are two of them in there are piezoelectric sensors that will develop a very small voltage acro ss them when they "hear" what is the beginning of a knock.The timing is the n adjusted by the computer accordingly. This was the way I understood it an yway. I figured with such a small voltage, keeping the modification grounde d would shield it from the electrical "noise" of the engine.
We reset the code and started the car. The check engine light came back on and a message I've never seen on the dash appeared: "reduced engine power". The car had no power, would not accelerate, and we had all we could do to just get it back in the driveway.
Now up until the time we made this modification even though we had the code there was no loss of engine performance noted. We just had this code that prevented us from getting a sticker. We haven't yet tried to plug the harn ess back into the engine to see if the power returns.
Is anyone familiar with this problem? Am I bypassing this nuisance sensor a dequately? We're not going to take any trips with this car. It's just a sec ond car and will be used by my wife to get the kids around town. As I've a lready said, it's just a second car and we'd really just like to be able t o use it.
If anyone can please help me to get this thing to run half way decently wit hout having to do this engine repair job, I would be very grateful. Lenny