I've heard conflicting reports that the knock sensor will or will not set off the check engine light, and whether or not its worth fixing (and is there 2 of them?) I would really like some definitive answers to this because my cel is on and I need to get an inspection Saturday.

 

First of all there is one knock sensor. It will not trip the CEL and that means that there is another problem. The knock sensor is a ghost code and will read 0304 if you read it manually or 0325 if you use and OBD-II scanner. Your CEL is not on because of the knock sensor and there is another problem with your car. Get the codes and post back.

Your car will not pass inspection with the CEL however if you can fix everything but the knock sensor, then you will most likely pass inspection with a faulty knock sensor as it has nothing to do with emissions.

 

thanks for the info, ive heard so many different stories about these things. ive had a bad ks since october but ive been told not to bother replacing it, so i think it may be an exhaust problem, im bringing it to get read on saturday, ill let you know the results, thanks again

 

No problem...I have the knock sensor code as well and I notice no difference in performance or gas mileage. I will replace it anyways cause i got the sensor for $55 from an org member and the wiring harness for $17 at the dealer. Seems worth it to clear the code for me.

 

If there's an autozone close by they do the reading for free.

Don't ever pay to have your car read, as you can also do it yourself.

 

Saves the $99 diagnostic fee at the stealership....thats for sure.

 

i ALMOST spent $99 on that at the dealer and the day before decided to search the net for info and ended up here -- haven't left since

 

ok, i used a code reader at work, and i got p0105 and p0420, along with the knock sensor code. does anyone know what these codes mean or where i can find out? thanks

 

did you check the stickies?

 

ok, thanks for the tip, i checked the stickies and went to the page that explains the codes, but i also saw a thread that says you need to convert the "p" codes (like p0420) into a different code and that will tell you what is wrong, is this what i should do, i got p0420 converted to 0702 and p0105 to 0803, does this make sense?

 

Now look up 0803 and 0702 in the stickies. 0702 is a bad cat usually I know that cause I got that code w/ my KS code also.

 

alright, thanks a million for your help guys, ive got it figured out now and just saved 100 bucks from going to a dealership. thats why i love this place

 

excellent work my friend, the more u come here the more u save.

 

okay, now ive got a new question, i stopped by to talk to my mechanic and he doesnt know what an absolute pressure sensor is, can anyone explain to me what it is and where its located and is it expensive to replace?

 

Wow you need a new mechanic. The Absolute Pressure Sensor (APS) connects to the MAP/BARO switch solenoid valve by a hose and detects ambient barometric pressure and intake manifold pressure. It receives a voltage signal from the ECU and returns a modified signal to the ECU. Voltage rises as pressure increases and should measure approximately 4.4V for 5 seconds after 5 minutes from starting engine and 1.2V about 6 minutes after the engine has been started. The two codes the APS may throw are P0105 and P0803. If an excessively high or low voltage is sent back to the ECU, check the harness or connectors (circuit is open or shorted) and the APS itself. If a low voltage is sent to the ECU under light load conditions, check the hoses between the intake manifold and the APS to make sure they aren't disconnected or clogged. Also look for intake air leaks, check the MAP/BARO switch solenoid valve, and the APS. If a high voltage is sent to the ECU during heavy load driving conditions, check the APS. Without a Consult to check voltages while simulating different driving load conditions, a full inspection of the system must take place. Start with the power supply. With the ignition off, disconnect the APS harness connector. First, check for water which should not be there. If it does exist, repair or replace the connector. If not, turn ignition on and check the voltage between terminal 3 and the engine ground. It should read 5 volts. Next, check the ground circuit. Turn ignition off and loosen or tighten the ground screw. Check harness continuity between the engine ground and terminal 1. Check the harness for short to ground and short to power. Check the Input Signal Circuit by disconnecting the harness connector to the ECU and checking for continuity between ECU terminal 61 and the sensor terminal 2. To check the APS, remove it from the bracket with the harness still connected and remove the hose from the sensor. With the ignition on, use a vacuum pump gauge to apply vacuum and barometric pressure to the sensor. Check the voltage between ECU terminal 61 and 25 (the ECU ground). At ambient barometric pressure, the voltage should read between 3.2V and 4.8V. Ambient barometric pressure changes due to altitude. For example, ambient barometric pressure at 1500 feet above sea level is roughly 95kPA; 0.0 is a vacuum and 101.325kPA is standard sea level. The MAP sensor has an aneroid capsule which determines the actual ambient pressure as a barometer does. Applying -26.7kPa of pressure should net 1.0-1.4v. Remember to calibrate the vacuum pump gauge. If the voltages are wrong, replace the APS.

 

wow, thanks, that pretty much explains it, btw hes a good mechanic, just old and portuguese, but hes fair and loyal.