hey guys,
my check engine light came on yesterday, and when i reset the ecu, it gave me two codes 03 04 and 05 04 respectively.
does anyone know what those two codes mean?
am i in trouble?
plus my overdrive light blinks from time to time when i start the engine, and when i drive for a while and stop at a light or something, the tachometer(rpm) fluctuates between 0 and 1 for a split second.
does anyone have any clue as regards whats up?

 

0304 means you have a bad knock sensor.
0504 means problems with your Automatic Transmission Control Unit Signal to ECU

The blinking overdrive light is probably because of the 0504.

ZuM

 

http://forums.maxima.org/showthread.php?threadid=235667

here is the info you need.

 

Pulled an 0304 today also. Im gonna try that test this weekend. If it is shot, how much would this be to replace? Also what makes it go bad?
Does gas matter cause I think the previouse owner ran 87, or is it just another one one nissans well bilt sensors. Cause you hear alot of these going out.
thanks

 

anyone?
Bump

 

replace knock sensor. use premium gas.

 

stock answer:

Once and for all: a bad knock sensor WILL NOT trip the check engine light, you must extract the codes from the ECU to determine if your sensor is (potentially) bad (code 0304). Some other hints as to a bad KS: poor acceleration below 3000 RPM (I was getting tired of being left behind at stoplights by Honda Civics).

A good KS will measure ~550 k-Ohm resistance between the left pin of the KS and ground. You can check the resistance without removing the KS by following the harness to the connector. The connector has two pins, only one of them hooks up to the KS, so try them both. The act of whacking on the KS with your wrench can (temporarily) start it working again, so checking the KS once you removed it may not give you the bad reading you suspect. Hint: the connector is not the green one closest to the KS (1995-1996 models – most likely 1994-1999), it is a few inches closer to the front of the car. A heat shielded wire leads into the bottom of it and there are two wires coming out the top, one clear and one black.

Low cost knock sensor sources: The dealer will charge you $160 or so for the sensor. I purcahsed a Nissan OEM sensor off of EBAY for $90 shipped. I have seen them for as little as $80 and routinely for $100-$110. Search for both “Maxima knock” and “Nissan knock” to make sure you get all the possible matches. You can get a Bosch sensors for $115 shipped from http://www.nissanpartstore.com/nissan_knock_sensor.html

Two good article on KS replacement:
http://www.skippynet.com/maxima/knocksensor.htm
http://www.motorvate.ca/mvp.php/507


Modifications to the Skippynet method

The article suggest using a 14” (or longer) ¼” socket extension to reach the KS retaining bolt. I found that using a 9” extension made it much easier to get the u-joint onto the KS bolt. To save money, I used two 3/8” drive extensions with a 3/8 to ¼ adapter, a ¼” drive u-joint and a ¼” 12mm socket (most of which I already had). Skippynet suggest using a 12mm flex socket, but being cheap I used a separate socket and u-joint so that I would have a more useful general purpose tool left over than the 12mm flex socket (better yet, I borrowed the u-joint and saved another $8). A 3/8” u-joint is a slightly bigger animal and in my opinion would make it hard to get the socket onto the bolt. It was not at all difficult to loosen the bolt using this setup. I had also borrowed a 16” extension and found it very difficult to get the socket onto the bolt head (I gave up after about 2 minutes, so it probably could have been done).

Once the bolt was out, I used a magnetic pickup to retrieve it (and eliminate the possibility of dropping it into the engine cavity where as you will find out soon, is not a very friendly place). With the bolt removed, you can pull the knock sensor out of the cavity by the harness and replace it. Next, I put the bolt into the new KS and used a small piece of tape to hold it in place while I stuffed it back into the engine cavity (again to eliminate the chance of dropping it in there).

Now the difficult part: I don’t see how you can locate the bolt into the hole and tighten it without stuffing your hand under the manifold. Others have reported that they used a claw type pickup to reposition the bolt in the KS, get the bolt started in the hole and then use the socket extension to tighten the bolt down.

If you have very large hands, you might try enlisting a girlfriend or your mom as others have done. I was able to get my hand in there and get the bolt hand tight, then it was just a matter of using the 9” extension/u-joint setup again to do the final tightening. Your hands will get cut up a little doing this, but no worse than I am used to with other auto repairs.

I was able to replace the KS in both cars in less than 1 hour including test drives using this method. The real key is using the skippynet socket extension method to crack the bolt loose. Once you have jammed your hand into the engine cavity you will realize how difficult it would have been to get a wrench on the bolt and loosen it.