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Car Forum / Nissan / Nissan Maxima / August 2005Require good diagnostic input and assesment
1995 Maxima GXE. 206,000 Kilometres. My Check Engine light came on solid, 6 days ago. The cars driveability has not changed, acceleration good, fuel consumption nominal, idle OK, 600 RPM, smooth engine, no hesitation nor straining, nor knocking. (pre-ignition). I use Good Quality fuel, SUNOCO, 94 Octane, almost all the time. I took the car in to the dealer today and had them read the codes, $48.00. They say, Catalytic Converter, $916.00, Rear O2 Sensor, $207.00 and Knock Sensor $518.00. The codes read out were, Catalytic - 2 events, O2 - 2 events, Knock - 1 event. Earlier this year, I put an aftermarket, custom made F-Pipe on the car, without mini-cat's, I have put over 15,000 Km on the cars since then, with no Check Engine lights coming on at all. My current thinking is that the O2, sensor may actually have gone bad, and that this causes the catalytic to look bad due to a difference between the front ad rear units and the knock sensor was just a random occurrence. I'd like to hear the opinion of some others here and how easy it would be to do some work myself, aka, O2 Sensor, knock sensor. rtt Do you have the exact code's that were pulled (i.e. the numbers)? The rear O2 sensor is the one behind the catalytic converter. This is easy to replace - the hardest part is getting the old one off. If you can't break it loose, any muffer shop should be able to heat it and get it loose for you for a small fee. The part can be bought for < $100 (www.oxygensensors.com). The knock sensor code may have been tripped by the O2 sensor code. It is a common occurence. I would suggest fixing the O2 sensor, resetting the ECU and seeing if any of the codes return. Caution: If the ECU detects only a knock sensor failure, it will not set the CEL - so even if the light is not on, check for codes. You can have autozone check the codes for free, or follow these instructions: How to get the code: http://vbxmaxima.8m.com/ecu.html What the code means: http://vbxmaxima.8m.com/ecudecoder.html There are more detailed definitions of the codes and what they mean here: http://forums.maxima.org/showthread.php?threadid=235667 You can pick up an after-market catalytic converter (if needed) and have yours replaced. OEM catalytic converters are expensive and the price you were quoted is nothing out of the ordinary for OEM parts/labor. Aftermarket cat's can be had for < $200. I can't speak to the quality differences between OEM and aftermarket, but I know that I will never pay the $700 for an OEM replacement if I ever have to go down this road myself. If the knock sensor does need replacement, this is also something you can also do yourself - with some creativity. The part itself is not cheap - dealer retail is ~$180. Labor is high because the recommended replacement procedure involves pulling the intake manifold off the car. Cheers, Nirav 96 Max GLE, 120k Hmm.. I just noticed you have a 1995... I'm not 100% if all 1995's were OBD-II compliant, so you may not be able to go to autozone to get the codes pulled and the DIY links to pull the codes may not be applicable... Sorry to throw you off. My comments on the work involved still stand. Nirav Thanks very much for the input. I was leaning toward the O2 sensor as being the actual fault and the catalytic being incidental as a result. Didn't know the Knock sensor did not flag the light, good to know, especially the false setting as that means it probably is the issue. I actually have the Nissan Shop Manual for the car, but I'm afraid I know very little about actually getting under the thing or what the various interrelationships on codes could be. I actually live in Canada, so I think AutoZone is out for me. The dealer wouldn't tell me the codes, they kept the printout in the file on the vehicle. I did see the paper, but it was all English, and I wasn't looking closely enough to remember the codes if there were any on the paper. I will definitely take the advice on the O2 sensor and do it myself and the catalytic looks like the way to go to, aftermarket. I'll have a look at the knock sensor in the manual and see what it looks like and where it is. Generally though, I am not a manifold puller, not that brave/experienced. > Do you have the exact code's that were pulled (i.e. the numbers)? > [quoted text clipped - 40 lines] > Nirav > 96 Max GLE, 120k Since you are across the border, I'm not sure of all the local parts sources, but for the O2 sensor, I would recommend www.oxygensensors.com. They are in the US, but have excellent prices and may offer shipping to you in Canada. Pick up an OEM style O2 sensor, and its just plug and play. The universal ones they offer will also work, but then you have to splice in your old connector and IMHO it's not worth the $$ you save. The knock sensor is located in the V of the engine. Here is a nice write-up on the replacement of the knock sensor. http://www.motorvate.ca/auto/maxima/knock/knock_sensor.htm (The site is VERY slow right now for me, but has everything you need for the KS and a variety of other Maxima maintenance). The trick to removing the KS without pulling the manifold is to use a 12mm 1/4" drive swivel socket on a 18" extension. If you fiddle enough, you'll get the old one loose. Once you break the bolt loose on the old one, its fairly straightfoward. When you get to point of needed to replace the KS, post back and we can give you some other tips to try first (checking the harness, cleaning the grounds, etc.). Cheers, Nirav Once again, thanks. Looks doable. I saved the links to all the various sites in my favourites list. rtt > Since you are across the border, I'm not sure of all the local parts > sources, but for the O2 sensor, I would recommend [quoted text clipped - 22 lines] > Cheers, > Nirav Page EC-50 to EC-51 of the FSM show how to pull the codes yourself. Regarding the ability to do it, it works on my '97, so I must assume it will work on your '95. I think in '99 the turn-the-ecu-screw thing disappeared. But following the procedure in the manual never worked for some reason. I googled and found this one which did: http://vbxmaxima.8m.com/ecu.html Anyway, I wouldn't worry about the knock sensor yet. Get everything else cleared out and fixed first. If you do get to the knock sensor code by itself one day, and decide to replace it, buy one off of eBay or jerryromenissan.com and you'll save a bunch vs. a local dealer retail price. I also bought a new piece of harness for it as well. Dave > Thanks very much for the input. > [quoted text clipped - 71 lines] > ----= East and West-Coast Server Farms - Total Privacy via Encryption > =---- > Page EC-50 to EC-51 of the FSM show how to pull the codes yourself. > Regarding the ability to do it, it works on my '97, so I must assume it will > work on your '95. Actually Dave, I'm not sure if the 95's were OBD-II compliant - so this may or may not work... Nirav Hmmmm. Just how many oxygen sensors are there in my car? I see the connector for the Front unit, Left Bank, and the Front unit, Right Bank and when I had the new F-Pipe installed, there were two sensors on the pipe, one upstream of the main catalytic and one downstream of the main catalytic. Doing the math, I then come up with four units, but the manual only identifies three units. The one I cannot find a reference for is the one in the exhaust pipe, upstream of the main catalytic. On another note, this aftermarket pipe did not have mini-cats, was it a bad decision to install this pipe and run the car without the two mini-cats in place? rtt > Page EC-50 to EC-51 of the FSM show how to pull the codes yourself. > Regarding the ability to do it, it works on my '97, so I must assume it will [quoted text clipped - 85 lines] > > ----= East and West-Coast Server Farms - Total Privacy via Encryption > > =---- You should have 3 O2 sensors unless you have a California emissions spec car and even with that said, I'm not sure if the 95's were different... Here are the ones on a Fed spec: 1. Front right bank 2. Front left bank 3. Downstream from the catalytic converter. http://www.courtesyparts.com/A32_O2-sensors.html Here is a TSB for a 2k Maxima, but it has pics for the O2 sensor locations for the Fed and Cal spec cars. http://maxima.theowensfamily.com/tsb/NTB02-051a.pdf I know of many others running with aftermarket y-pipes without pre-cats - but am not sure of the long-term effects. I imagine the engineers put some thought into that design (from an emissions perspective), so I would tend to think it's a bad idea. Without the two-precats, your main catalytic converter is having to do a lot more work -> perhaps leading to its failure. The O2 sensor(s) may have gotten contaminated as a result of this too (since there is less overall cleaning of the exhaust gas). This is just opinion however, not based on any experience or evidence. I can get a NGK or a Bosch unit here in Ottawa for $136.00CAD or $134.00CAD respectively, which is $111.00USD and $109.00USD approximately. Which brand is recommended? > You should have 3 O2 sensors unless you have a California emissions > spec car and even with that said, I'm not sure if the 95's were [quoted text clipped - 22 lines] > exhaust gas). This is just opinion however, not based on any > experience or evidence. Bosch is the OEM for our Nissan O2 sensors... but NGK is very reputable too. I don't think you can go wrong with either. Nirav > Hmmmm. > [quoted text clipped - 119 lines] > http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups > ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- The purpose of the pre-cats is to provide cleaner tailpipe emissions during the car's warmup process. Once the car's warmed up, the exhuast is hot enough for the main cat to do its job properly. No major effect except maybe in the really really really long term in that the main cat may have a wee bit shorter life span. No biggie. CD |
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