Nissan Maxima How-To Page

Welcome to Cullens 4th Gen Information Page. Questions concerning the information here should be directed to the Maxima forum on NICOclub.

How To Clean IAC valve:

  • Tools needed:

  • 10 and 12 mm sockets

  • 3 inch socket extension

  • universal joint (swivel pivot socket thing)

  • 12-inch rachet (a short rachet may not work - need something to apply a lot of torque to loosen the bolts)

  • Philip's screwdriver

  • rag

  • throttle body cleaner

  • 1. Unplug the 4 connectors from the IAC assembly. Undo the hose that connects teh IAC to the intake assembly.

    2. The metal bracket holding up the gray-colored connector is blocking one of the IAC mounting bolts. Using a 10mm socket, remove the bolt that holds the metal bracket. The bolt is just below the purple connector - you have to twist your head and crane your neck around to see the bolt.

    3. Remove the 3 mounting bolts using the 12mm socket. The lowest bolt may require the Universal joint.

    4. Pull out your IAC valve and clean it w/throttle body cleaner, rag, and old toothbrush.

    You may even want to separate the plastic valve to clean it more thoroughly. Use a philip's head screwdriver, but make sure it is a snug fight. It's on there tight and if you don't have a good fitting screwdriver, you could ruin the screw head.

    Reinstallation is just the reverse of these steps. It may be easier access to the IAC if you remove the whole air intake assembly, but it's not necessary.

    Testing the Knock Sensor (KS): - The KS MUST be checked with a digital ohmmeter. Analog ohmmeters may cause damage to vehicle.

    1) Raise the hood. View the engine from the driver's fender. Look into the deep valley between the cylinder banks and below the intake manifold. Identify the KS as a black item fastened to the block by a single vertical bolt. A wire harness wrapped in black leads toward you, out of the valley. That is the KS sub-harness.

    2) Follow the KS sub-harness to it's nearest connector. This is connector F121. It is located near the upper right-hand corner of the valve cover of the forward cylinder bank, as viewed from the front of the car.

    3) Disconnect F121. You have to do a "press the latch and wiggle and pull" to disconnect it. F121 has only two pins; if you see more than two pins, you have the wrong connector. Use a digital ohmmeter capable of measuring more than 10 Megohms. You want to measure the pins of F121, not the sockets of the matching connector. Measure the resistance between a good ground (such as the battery negative terminal) and pin #2 of connector F121. On my car this is the highest of the two pins, the one closest to the front of the car. The factory spec is 500 - 620 Kohms.

    More on the dreaded KS:

    Knock Sensor Diagnosis, Test and Installation

    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), and reduced gas mileage.

    If you don’t already own a Haynes or Chilton manual, get one. In addition to telling you how to extract the codes and locate the KS, there is a wealth of useful information for the do-it yourselfer. I am very cheap, but this an area well worth spending the $20 or so (I bought mine off of EBAY for $10 shipped).

    The ECU is located behind the center console on the drivers side. It is accessible by removing the plastic cover panel right next to the gas pedal. The ECU is a metal box with a screw on the side covered by a piece of tape. Peal back the tape to get at the screw. With the ignition in the “On” position, turn the screw all the way clockwise, hold for at least 2 seconds, turn it all the way counterclockwise. Your CEL will now start flashing out any codes stored in the ECU. The codes are two digit numbers. The first number is signaled by long flashes, there will be a two second pause, and the second number will be indicated by a series of short flashes. Long-long-long-pause-short-short-short-short = 0304 (KS fault). There may be more than 1 code in the ECU, they will be flashed out sequentially and the whole sequence will repeat. To clear the codes from the ECU, follow this sequence: clockwise, hold, counterclockwise, hold, clockwise, hold, counterclockwise.

    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 that gets in the way of sticking your hand into the engine cavity (1995-1996 models – most likely 1995-1999). The correct connector 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 purchased 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

    Two additional articles on KS replacement:
    NICO Thread

    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(ish) part: I don’t see how you can locate the bolt into the hole and get it started without stuffing your hand under the manifold. Others have done it using a claw type pickup to position the bolt so no harm in trying. If you have very large hands, you might try enlisting a girlfriend, your mom or a small child 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 the term “bloody stump” that gets thrown about is quite an exaggeration.

    I was able to replace the KS in both cars in less than 1 hour including test drives using this method. Post installation I got back the power of my VQ and gas mileage increased by 2 MPG.

    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.

    How to reset SRS(air bag) light:

    Open the driver's door. Note the rubber covered button located low on the B pillar, a button which is pressed by the door when the door is closed. This is the Driver's Door Switch (DDS).

    Turn the ignition from OFF to ON. Press the DDS at least 5 times within 7 seconds after turning the ignition switch ON. Turn the ignition OFF. Close the driver's door. Start the engine.

    If the airbag warning lamp is still on (or still flashing), there is a fault in the Supplemental Restraint System which must be diagnosed and repaired. This is a job for your local friendly Nissan dealer.

    How To change Motor Mounts:

    Here are the tools it takes to complete the job:

    1) floor jack
    2) two 17mm short sockets
    3) ~2.5' of 1/2" extensions
    4) 1/2" rachet
    5) 18" 1/2" breaker bar
    6) jack stands
    7) 10mm socket and 1/4" rachet
    8) "Bottle" jack
    9) torque wrench
    10) penetrating oil (preferably PB blaster)
    11) anti-seize

    Installing new engine mounts:

    1) Jack the car up, secure with jackstands, and remove the driver's side wheel

    2) spray penetrating oil on the bolts and nuts that connect the mount to the engine

    3) Using the breaker bar, 2.5' of extension, and a 17mm socket, feed everything through the driver's side wheel well to the rear engine mount bolt and loosen the bolt. This takes some odd leverage and if you're not a decently strong guy, you might be screwed. Also, the amount of extension greatly reduces you're the torque you can generate. You also have to careful and keep the socket on the bolt because the last thing you want to do is strip the head of the bolt. Once the bolt breaks loose, just loosen it, but don't remove. On the rear mount, there is only a bolt. The nut is welded to the "ear" of mount that's connected to the engine block.

    4) Using the 10mm socket, remove the two bolts that attach the splash guard to the cross member. Pull the guards down out of the way best you can. They don't need to be removed.

    5) Go to the front mount. Using the breaker with a 17mm socket and a rachet with a 17mm socket, break the bolt and nut loose that attaches the mount to the engine. Again, this takes some serious muscle because the leverage is odd and the bolt is on there with ~95 ft/lbs. Again, just loosen this bolt.

    6) Take a piece of 2X4 wood and the bottle jack and place the wood between the bottle jack and transmission casing. Jack the tranny up ~1/4". What you are doing is supporting the engine and tranny.

    7) Using the breaker bar and a 17mm socket, remove the two front and rear chassis to cross member bolts. Keep the front bolts seperate from the rear bolts BECAUSE THEY ARE DIFFERENT! Something that caught my attention was that these bolts, both front and rear, were only on with about 30 ft/lbs of torque. My Chilton's and FSM both said these bolts are suppose to be torqued to 95 ft/lbs. I'm a bit perplexed at why they were so loose.

    8) Once the cross member to chassis bolts are out, wiggle out the mount to engine bolts and nuts, and drop
    the cross member. It will weigh about ~25lbs.

    9) With 17mm sockets on both the breaker bar and rachet, remove the bolts and nuts that connect the mounts to the cross member. There are four of them (two for each mount). Again, leverage of tough and those suckers are torqued to 95 ft/lbs.

    10) Install the new mounts to the cross member. Put some anti-seize on the nuts and torque the rear mount bolts/nuts to 75-95 ft/lbs. The reason you use anti-seize is to help the threads stay lubricated and you also get a more accurate torque reading. On the front mount just insert the FRONT bolt into the mount and put the nut (ant-seize it) on finger tight (ie only one of the two bolts on the front mount is attached to the cross member at this time).

    11) Lift the cross member into place and slide the rear mount to engine bolt into place and tighten to ~40 ft/lbs.

    12) Install the two rear cross member to chassis bolts so that they are slightly tight (~20 ft/lbs, anti-seize

    13) Slide the front mount to engine bolt into place and finger tightening the nut (anti-seize it).

    14) Install the two front cross member to chassis bolts so that they are slighty tight (~20 ft/lbs, anti-seize

    15) Now the fun part. If your car was like mine, you'll notice that you will not be able to install that front mount to cross member bolt/nut (step 10) because the holes on the mount and cross member don't line up perfectly. Believe me, I tried every different way under the sun to make this work and what I did was the only option on my car. I removed the bottle jack from the tranny (tranny and engine are fully supported by the mounts now) and situated the bottle jack so that it was able to jack up the driver's side lower "ear" of the mount. I slowly jacked up and the mount and cross member holes lined up on that side. The bolt slide through, but now the other side the still wasn't completely lined up and bolt couldn't fully slide through. So I then took my floor jack and used it on the passenger side lower "ear" on the mount. With just some slight jacking, the holes lined up and the bolt slide through. I lowered the jacks and installed the nut (anti-seize it).

    I have heard of guys having to enlarge the mount's holes to compensate for this lining up problem. To me, it wasn't an option. I was going to make it work the right way using wrong way methods :LOL:

    16) Now all the bolts/nuts were in place and I began torquing all of them to ~77-95 ft/lbs as called for in the FSM. Seeing that the torque numbers are so high, it appears Nissan thinks that these bolts are very important. I
    suggest torqueing them right.

    17) I reinstalled the 10mm splash guard bolts, put the tire back on, and lowered the car.

    18) I started her and took her on a test drive and everything seemed fine. There was a little less vibration and 50% of the drivetrain "slop" was gone. The 7-year old mounts I removed weren't torn, but they were a bit softer than the OEM replacements I installed.

    O2 sensors:

    Upstream O2 sensors:

    Necessary tools:
    *3/8" drive ratchet
    *16mm O2 sensor removal ratchet (rent it from Autozone for free)
    *OEM upstream O2 sensor(s)
    *PB Blaster (or WD40)

    1. Put the front end of the car on ramps or jackstands

    2. Spray the O2 sensors with PB blaster (or other lubricant) to make removal easier; wait ten minutes.

    3. Using the O2 sensor ratchet attachment, loosen the current O2 sensors that are installed in the "Y" portion
    of the Y-pipe

    4. Trace the sensor harness up to the engine bay and unplug it. One will be close to the cabin, to the left of the spark plugs; the other will be clipped by the radiator, towards the front of the car

    5. Cut the plastic things holding the harness; there will be multiple ones

    6. Completely unscrew the O2 sensors

    7. Plug in the new sensors to the now-empty connectors that the old sensors were attached to

    8. Dangle the sensor from the engine bay to the underbody of the car, taking care to do it SLOWLY so you don't damage the sensor

    9. Put a little anti-seize on the threads of the sensors (if there isn’t any already)

    10. Screw 'em in and you're done.

    Downstream O2 sensor:

    Necessary tools:
    *12mm wrench
    *OEM downstream O2 sensor
    *PB Blaster (or WD40)

    1. Put the rear end of the car on ramps or jackstands

    2. Locate the downstream O2 sensor; it is in rear-half the catalytic converter, on the driver’s side (middle
    of the car is where you should be looking)

    3. Spray the sensor with PB Blaster or WD40

    4. Trace the harness to the underbody of the car

    5. Pull on the harness until the rubber seal pops free

    6. Disconnect the old sensor from the harness

    7. Apply anti-seize to the new O2 sensor (if it doesn’t already have some); take care not to get the compound on the sensor head

    8. Screw in the sensor

    9. Connect the new sensor to the harness

    10. Jam the excess wiring back into the hole and close it up with the rubber seal

    11. Using one of the supplied zip ties, secure any slack wiring.

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