MY CHeck engine light came on today. The car is running fine.....with no problems......oxygen sensor? what could it be.......how should I proceed?

First thing is to always check the gas cap to make sure it is tight. Yeah, I know, but that is always the first step....

If you care to get an OBDII scan tool, you can connect it to the DLC which is located under the instrument panel fuse box cover. You should then be able to pull the codes to help determine what the problem is. You can also take it into a regular car care center to have the codes pulled.

If you don't have one or don't want to purchase one, you can get the codes from the PCM. The PCM is located under the console on the drivers side floorboard near the gas pedal. Remove the cover by removing two "twist screws). You should see the PCM and a screw area for self diagnostics. Turn the car on (do not start), turn the screw all the way clockwise (careful not to force it as it is fragile). Wait 2 seconds, and turn it back to the origional position. The CEL will start flashing a number of long or short flashes.

FOR EXAMPLE:

(LONG) (LONG) (LONG) (LONG) (SHORT)(SHORT) ....means trouble code 04 02

ANOTHER EXAMPLE:

(LONG) (LONG) (SHORT) (SHORT) (LONG) (LONG) (LONG) (SHORT) (SHORT) tells you there are two codes: 02 02 and 03 02

The flashes will continue, so keep making notes of the code(s) until they repeat.

Using the codes, you can find out the scan tool trouble code by comparing below. At this point, you can search for the solution to the codes..

P0000 --- 0505 P0100 --- 0102 P0105 --- 0803 P0110 --- 0401 P0115 --- 0103 P0120 --- 0403 P0125 --- 0908 P0130 --- 0307 P0130 --- 0503 P0131 --- 0411 P0132 --- 0410 P0133 --- 0409 P0134 --- 0412 P0135 --- 0901 P0136 --- 0707 P0137 --- 0511 P0138 --- 0510 P0139 --- 0707 P0140 --- 0512 P0141 --- 0902 P0150 --- 0303 P0151 --- 0308 P0152 --- 0415 P0153 --- 0414 P0154 --- 0413 P0155 --- 0101 P0157 --- 0314 P0158 --- 0313 P0159 --- 0708 P0160 --- 0315 P0161 --- 1002 P0170 --- 0706 P0171 --- 0115 P0172 --- 0114 P0173 --- 0806 P0174 --- 0210 P0175 --- 0209 P0180 --- 0402 P0300 --- 0701 P0301 --- 0608 P0302 --- 0607 P0303 --- 0606 P0304 --- 0605 P0305 --- 0604 P0306 --- 0603 P0325 --- 0304 P0335 --- 0802 P0340 --- 0101 P0400 --- 0302 P0402 --- 0306 P0403 --- 0515 P0420 --- 0702 P0430 --- 0703 P0440 --- 0705 P0443 --- 0807 P0443 --- 1008 P0446 --- 0903 P0450 --- 0704 P0500 --- 0104 P0505 --- 0205 P0510 --- 0203 P0600 --- 0504 P0605 --- 0301 P0705 --- 1003 P0705 --- 1101 P0710 --- 1208 P0720 --- 1102 P0725 --- 1207 P0731 --- 1103 P0732 --- 1104 P0733 --- 1105 P0734 --- 1106 P0740 --- 1204 P0744 --- 1107 P0745 --- 1205 P0750 --- 1108 P0755 --- 1201 P1105 --- 1302 P1148 --- 0307 P1168 --- 0308 P1220 --- 1305 P1320 --- 0201 P1335 --- 0407 P1336 --- 0905 P1400 --- 1005 P1401 --- 0305 P1402 --- 0514 P1440 --- 0213 P1441 --- 0801 P1444 --- 0214 P1445 --- 1008 P1446 --- 0215 P1447 --- 0111 P1448 --- 0309 P1490 --- 0801 P1491 --- 0311 P1492 --- 0807 P1493 --- 0312 P1605 --- 0804 P1705 --- 1206 P1706 --- 1003 P1760 --- 1203 P1900 --- 0208 P1900 --- 1308

are u sure the pcm is on the 1996? i dont see anything that looks like which you have described nor do i see anything in the owners manual about a self test.........please advice

where can i find this obdII scan tool?

From what I have seen, the '96 Max and '96 I30 should have the ecu in the same location:



You can get a scan tool from places like AutoZone. In fact, they would probably be willing to hook up and tell you the codes...

what does po125 mean and po325....sensor 1 circuit malfunction

From "looking around", I have found the following:

Diagnostic Trouble Code 0908 indicates a bad Engine Coolant Temperature Sensor, and also says the ECTS always says "cold engine" and this prevents the Engine Control Module (the computer) from going into closed loop mode. This could indicate a bad sensor or a stuck-open thermostat.

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.

Important note: the dealer can do a more thorough test with his CONSULT electronic tester. The resistance test described here is a useful but limited test. A Knock Sensor which fails this test is definitely bad. However, a KS which passes this test is not guaranteed to be good.

well i am having no cooling problems at all.............car runs fine......maybe something else trigger the knock sensor code....what are symptoms of a bad knock sensor.....? what i did was erased the codes to find out if they will occur again.........i think u might be rt....stat just might be stuck open......if they coolant sensor was bad...the car would run hot.....or maybe the resistance in the sensor is dropping and about to fail...........please advise...

If the stat is stuck open, it would take quite more than 2 min for heat to start coming out. If the vehicle takes a long time to warm up, that might explain it. As far as the codes and such, that is all I could find on troubleshooting them. I believe most of this information is from the Chiltons manual for the vehicle....

audtatious pretty much has you covered from all angels on this. only thing I will add from experiance on the line is: A coolant temp sensor going bad on a max/I30 is not that uncommon have done several of them over the last 8 yrs with nissan. Knock sensor same story in this forum there is a write up that applies to replaceing the knock sensor on your model vehicle. The knock sensor going bad is pretty common on all nissans. Alot of times its related to the connection between the sub harness and the sensor. When you replace the knock sensor also do the little subharness attached to it.

found it and it happens to be the exact year

http://www.nissaninfiniticlub....51191

i am not sure what you mean by subharness.......nistech........i looked at the knock sensor and it sure seems hard to get to. is the subharness another part....or the connector to the knock sensor...........

it is the harness that plugs into the knock sensor. it runs about 12 inch then plugs into another connector from the main harness.

by the way the knock sensor will not trigger the CEL.

well how do u explain the check engine light coming on? the other code was for the coolant sensor............how should i proceed.? car does not run hot? does this means the coolant sensor is going bad? and the knock sensor is going bad........i erased the codes and it has not come back on.........

it could mean you have an intermitten circuit problem. could be going open somewhere in the harness. there was a TSB which talked about wires being stretched on the R/H strut tower where the main engine harness spans from the tower to the timing cover on the engine. try wiggling that harness and see if the light pops back on. also wher audtatious told you to gain access to the ecm go on the other side and see if maybe the evap is dumping water on the ecm connector[ have seen that a few times]

The light was on as a result of the Temp sensor not the knock sensor.

well i did shack the wires near the strut tower........yesterday because i thought the same thing. and it did not come back on.......and i wiggle the knock sensor wire....did not come back on..........and if i am not mistaken that strut tower wire harness can cause stalling which i have not had............;however, the scan tool said po325 and po125 sensor 1 circuit malfunction.......and something about fuel efficiency.......i did not a slight lose of power when the light pop on. please advise

The harness problem on the tower can have any number of problems not just stalling. the loss of power was probably due to it going into failsafe when the coolant temp went open. if the light is not on now I say let it go for now and see if the light randomly pops back on. When and if it does take note in exactly what you were doing when it came on, i.e. accelerating from a stop, driving at a steady cruise speed, braking, what was the temp outside, did you have any accesories running. All that is helpful in locating a stubborn problem such as yours.

Off subject sort of but as an example I have been trying to recreate a problem on an 04 max today and yesterday. I found that if the interior was to cool down the problem goes away but if I allow the car to sun bake the problem is constant. So it puts me outside trying to diagnose it. It took several times of recreating the problem to realize what the circumstances had to be to have the failure. So any thing you note may be of importance if you still cant isolate the problem should the lite come back on. It may take a few occurances till you catch the common thread to the failure.

Make sence??? I tryied to explain that best as possible..lol

Scott

lol yeah i got you.........i know sometimes its hard 2 locate a problem. should i replace the coolant temp sensor? and knock sensor since i got a code or thinking something else caused those codes.........when i came on i was accel from a coast....it was about 70 degrees........nothing on but radio and sunroof open......

accel is the key as that is when the engine torques and wil move the harnesses. try just wiggling the coolant temp connector itself while its still plugged in and basically follow the logical route of the coolant sensor wires through the main loom moving the loom around a bit as you go to see if you can disturb the circuit. I am not saying open the harness loom just wiggle it where you think the coolant wires are running through. I do want to say replace the coolant temp sensor since I have replaced several myself on the A32 but I am only about 80% sure that is infact your problem. On the knock sensor definitly as that is a very common problem on all nissan models. but be sure you get the little harness that runs from the knock sensor to the main harness. Again the knock sensor will not illuminate the check engine light. I suspect if you check for codes in the computer now you will find po325 stored again.

ok nissan tech.....i will replace the knock sensor..........its like 115 bucks ...how much is that little harness and how do u replace it........i see that is has 2 grounded wires also to the knock sensor. the coolant temp sensor is only 10 bucks........maybe i should just replace it.........when it goes bad can it cause the car to overheat or does it have a failsafe......like the ecm does for the knock sensor.............i am going outside rt now and wiggle some more wires if i get nothing then.........i will write u back

when it goes into fail safe it substitutes input values to the ecm If you were to hook up a scan tool to the computer and moniter the coolant temp you would not see anything wrong [ unless you have experiance dealing with it] The way to tell is let the temp rise 20 or 30 degrees on the scan tool, shut the car off and wait 10to 15 secs and restart it. the temp will be right back to where it was the first time you started it. I think its like 104 degrees. and it will slowly rise again. The reason is, It assumes the car is cold when you start it and it starts a timer and guestimates about how much the temp will increase over a certain time frame. The temp on your scanner will rise 2 degrees at a time about every 5 secs till it gets to approximatley 192 degrees??? not sure on that exact number. then it allows the car to keep itself cool with the t-stat and the fans. When its in fail safe the fans will stay on constantly they never shut off till it sees the failure fixed. When you are wiggling the coolant temp harness you will know when you break the circuit cause immediatly upon the break the cooling fans wil kick on.

ok........well the fans are not on.....they come on auto as usual.......and the car is not running hot or anything......??????? confused

did the CEL come back on since it was cleared?

no sir.......it has not come on at all.

You could also try to activate it ,since this problem occured on accel, you could place the car in drive. Hold your foot on the brake and give it a little accel to get the engine to torque a bit [power brake it] see if that makes your light wink on. If this doesnt make it do it I say let it go for now and not worry about it till the light comes back on. if the light does come back on later down the road see if at the moment it comes on you have heat from your vents if yes replace the sensor if no replace the T-stat.

ok..thanks for all your help.........but i should proceed with knock sensor.....rt?

pull the codes and see if it still has the code for the knock sensor first. I had never noticed the price of that sensor before that is pretty steep. you do need to address that problem with the knock sensor for sure but try a little trick first and see if you can save he potential 160 bucks for those parts. pull the knock senor out and perform the ohms check aud mentioned earlier. if the reading is with in spec. try taking a very fine peice of sand paper and slean both the surface on the block and the surface of the sensor mounting area. also use a small pointed scribe on the harness pins in the connector that plugs into the sensor and give them a little bend inward where the female pin splits in the connector. this will give the connector a tighter fit on the sensor pins. Then see if the code ever comes back. If the sensor fails the ohms check then yes replace it. The sensor is difficult to get at so if you just really dont want to waste time and you have the money to spend on the sensor just replace it.

Awesome info NISTECH. I know how to pull the codes and reference them, but a troubleshooter I am not