i looked them up and they are the EGR and the knock sensor. well i did some searching and i have found people with teh same code combination and they were told to replace the o2 sensors. whats the deal with that? is it the 02 sensors or the first 2? also, i my gas milage has gone to crap, i have about a 1/4 tank left and i have only gone 210 miles. normally i get 350-400 miles per tank. i assume they are related. so i am wondering if it could be horrible gas although it is the same station i frequent. EGR and Knock sensor are both gas related items. anyway, any help would be much appreciated.
oh, and it was 3 long ones and 4 short flashes, and 3 longs and then 2 shorts. thats 0304 and 0302 right?

 

Reset your ECU, and if both of them come back, change whatever's wrong with the EGR, and after than, reset again, and if 0304 comes back THEN change your knock sensor...

 

I had 0304 for the longest time. After a 3rd inspection Nissan finally found the problem, it was a shortage in one of the knock sensors. Hopefully, your problem can be easily fixed. Try testing out the wiring of the knock sensors with a multimeter and see what you find. (Use a search, I've never done it myself before)

 

The 02 sensors should have nothing to do with this. Sometimes, the knock sensor code gets tripped as a result of other codes, but in this case, it would be hard for the EGR system to cause a knock sensor code. Still, I would try to fix the EGR issue first, reset the ECU and see what comes back codewise.

BTW, both EGR and knock sensor issues could send your gas to hell quickly.


DTC 0302

Diagnostic Trouble Code 0302 points to a problem with the Exhaust Gas Recirculation system.

The malfunction isdetected by the Engine Control Module when no EGR flow is detected under conditions which call for EGR.


Possible causes include:
- The electrical harness or connectors (valve circuit open or shorted)
- The EGR valve is stuck closed
- Weak or dead battery
- The EGR passage is clogged
- Faulty EGR temperature sensor circuit
- A leak somewhere in the exhaust system

The EGR Volume Control Valve may be tested with an ohmmeter. Disconnect the electrical connector. Looking at
the connector half which is attached to the EGRVCV with the latch at the 12 o'clock position you will see two
rows of three terminals. The top row is numbered 1-3, right to left. The bottom row is numbered 4-6, right to
left. Measure the resistance between these terminal pairs:
2 1
2 3
5 4
5 6
... all resistance values should be 20.9-23.1 ohms at 68 degrees F.

Reconnect the EGRVCV connector halves. Turn the ignition switch ON OFF repeatedly. Verify that the EGRVCV
shaft moves smoothly forward backward according to the ignition switch position.

The Exhaust Gas Temperature Sensor may be tested with an ohmmeter. The specifications are ...
- at 32 degrees F, 0.68-1.11 Megohms
- at 122 degrees F, 0.09-0.12 Megohms
- at 212 degrees F, 0.017-0.024 Megohms

and

DTC 0304

Diagnostic Trouble Code 0304 points to a problem with the Knock Sensor.

The KS is attached to the cylinder block. It senses engine knocking using a piezoelectric element. A knocking vibration from the cylinder block is senses as vibrational pressure. This pressure is converted into a voltage signal and sent to the Engine Control Module (The computer).

This malfunction is detected when an excessively high or low voltage from the KS is entered to the ECM.
Possible causes include...
- the harness or connector (The KS circuit is open or shorted).
- the KS


The KS may be checked with an ohmmeter.

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.

The manual says you have to remove the intake manifold to replace the KS. However, I think that a person with good dexterity and a 10mm ratcheting box wrench could replace the KS without disturbing the manifold.

 

Mr Iwannabmw:

Maybe you can help me here? My 99 max is showing both a 0201 and 0304 ECU code (ign signal circuit + knock sensor). Do you think IGN SIG Circuit issue could be causing the Knock Sensor code too? Seems strange that I'm getting these together? I've reset the ECU a couple of times over the last 3 weeks and same 2 codes come up. Car idles a bit rough when cold, once it warms up all is fine.

Any ideas would be appreciated?

 

Anytime a knock sensor code is seen with another code, I would fix the other problem first and then reset the ECU. After driving for several days I would check the codes again, regardless of whether or not the light has tripped. If 0304 comes up, the knock sensor is indeed faulty.

There seems to be a bunch of 99's running around with coil problems, so 0201 is not too surprising. One or more of your coils is probably faulty. The possibilities listed that would trip this code are:

- Harness or connectors (the ignition primary circuit is open or shorted.)
- Power transistor unit built into ignition coil
- Condenser
- Crankshaft Position Sensor (REF)
- Crankshaft Position Sensor (REF) circuit

Note: The crankshaft position sensor has it's own code as well.

I would also recommend a search on the coil issues that have been occurring recently to help you troubleshoot the problem.

 

I'm surprised the 0201 hasn't come up with any other codes besides the knock sensor...usually it comes up with some kinda cylinder misfire codes with it...strange....is your CEL light on? and does your car heavily vibrate at idle, and does it feel like your running on 4 cylinders?

 

Hi, thx for the reply and follow-up.

Yes the check engine light is on but car only runs slightly rough (very mild). This problem is more intermittent than steady --- doesn't always happen when car is started, just sometimes. I was hoping after one of the ECU resets to get a faulty cylinder code, but no luck here.

If it continued rough, I'd start disconnecting the coil packs one by one to see if I could find the faulty one by elimination. But this doesn't happen enough to do it that way. Seems like a similiar complaint from others posting issues like this?

 

i have the same problem you are describing but i can add a little confusion to the subject. 0304 and 0302 both pop up with me. then i got a new engine and it still pops up and the shop checked both components and replaced both components at no charge and the code still pops up.they said the problem probably lies in the wiring harness somewhere.please help