Service Engine Soon light

[chak5050]

I have a 2000 Nissan Maxima 5speed, which has had the Service Engine Soon Light on for around 6 months. The Code is for Catalyst Inefficiency Right Bank. The Items I've replace so far include; catalyst converter, right bank upstream o2 sensor, MAF sensor, and spark plugs. I am also having a surging/bucking issue during low RPMs. This surging only happens when the engine is cold, and the outside temperature is relatively low. I replaced the MAF sensor thinking it would fix this, but it didn't. Any help will be appreciated.

edit....the code number is P0420, I know there is a TSB for this but my car is over 80k miles so it won't help, I'd rather not take it to the dealership.

[Nahkapohjola]

Mileage?

The error code may be caused by 'anythin'. First tuneup: check for typical 'wear'.
- Throttle, idle adj etc get sooty, may jam already after 60k. Cleanup time?
- Coilpacks may start going after 100k.
- Vacuum hoses, check for brittled ends. Intermittent vacuum leak after MAF?
- Fuel pressure ok? Test.
- Injectors ok? Cleaner might hlp if leaky.
- start from checking charge voltage, grounding etc contacts
- check that the O2 signals are healthy at ECU (easier access via connectors under hood)
...check page 14, click link below - see also p9,10,15

[chak5050]

The car has 98k miles. I forgot to write that I've cleaned out the throttle, checked for vacuum leaks, and exhaust leaks. I've also run some cheap fuel system cleaner through, however I think my next step is to get some better cleaner.

[Nahkapohjola]

Originally Posted by chak5050

.... cleaned out the throttle, checked ....

If idle adj stepper motor jams intermittently, dropping to idle becomes jerky. The stepper motor may behave better when warm... Clean & lube may help.
Intake air: Cold rubber parts may leak while after warmup seat better and seem ok.
If airleak is suspected, spraying smtg [water?] which momentarily blocks leaks can be used to pinpoint a leak.

[chak5050]

This light is still driving me crazy, in the last week I've spent some time looking at this. I cannot find any vacuum leaks, all hoses are connected and none are cracked/brittle. I took my car to a friend who's a mechanic at a local shop to hook up the scanner. He told me the fuel trim looked good, and the 02 sensor seems to be alright. I ran 1/3 can of SeaFoam through throttle body, and the rest in the gas tank (no clue if it did anything, sure made my car smoke like crazy though). One thing I noticed is when I pull the throttle cable under the hood I hear a vacuum sound but I think it's just the air being sucked through the throttle. Is there anyway to find out if I have a bad ignition coil other than replacing them? Would a bad ignition coil create the problems I described in the first post?

[Toolman5523]

bad coils usually don't cause a surge or bucking concern, they just run rough. most of the times when coils go bad they don't get better as temp increases, but rather get worse. when you changed spark plugs did you go back with factory ngk platinum, or did you go the aftermarket route? many times not running the correct plugs can really jack a with a nissan. dumb question, are you sure that you changed the right cat converter? when you changed the maf sensor did you also re flash the ecm, the replacements require it. the upstream o2 sensor has nothing to do with the cat converter, but rather the rear does. it's sole purpose is to monitor cat efficiency, that's it. I believe the tsb you are referring to involves re flashing the ecm to "dumb down" the processor and ignore that particular cause of the code. until you re flash the ecm I really don't think you will ever be rid of the light.

[Nahkapohjola]

Coilpacks start to go 'at 100k'. If one is bad, buying one, swapping until hit jackpot - replace only one and save. If two are bad - too bad one doesnt hlp. If three are... etc. Its part of 'routine maintenance' to swap all - all systems are built just to milk all loose money from all that is moving.

The error code is either just 1. errorcodegenerator related -or- related to 2. real authentic bad exhaust problem = O2 problem detection.

1. 'Any' issue here can be the cause, starting from alt generated charge ripple to intermittent sensor(s) failure; see pages 9,10,23 also http://www.cardomain.com/ride/748507/14

2.
- If u now have Bosch plugs, try hittin next six magpies - buy/swap to ngk plat before doing anything more. If NGK, Check now all plugs, compare to www.ngk.com troubleshoot pics. all ok? Check gaps. Check for healthy spark visually (when cold).
- swap all coilpacks
- mother nature: moist weather means condensing. On certain conditions, even the plugs may be 'swimming' in their wells: condensed water runs down causing shorts until warmup evaporates all this.
- for some reason there has been coolant splash over engine compartment in past history (you DONT know even if u are first owner). Glycol crystals suck moist from air, critically located and then this causes shorts when cold.
- you swapped wrong O2 and/or it was DOA dead on arrival
- ECU has had it or doesnt get juice enough: all troubleshootin starts from checking voltages, groundings

[chak5050]

Originally Posted by Toolman5523

bad coils usually don't cause a surge or bucking concern, they just run rough. most of the times when coils go bad they don't get better as temp increases, but rather get worse. when you changed spark plugs did you go back with factory ngk platinum, or did you go the aftermarket route? many times not running the correct plugs can really jack a with a nissan. dumb question, are you sure that you changed the right cat converter? when you changed the maf sensor did you also re flash the ecm, the replacements require it. the upstream o2 sensor has nothing to do with the cat converter, but rather the rear does. it's sole purpose is to monitor cat efficiency, that's it. I believe the tsb you are referring to involves re flashing the ecm to "dumb down" the processor and ignore that particular cause of the code. until you re flash the ecm I really don't think you will ever be rid of the light.

Yes, I did replace with the NGK patinum plugs. I've read that I needed to flash the ECM as well, I just figured it would still get better readings from the new MAF. Looks like I'll be heading to the dealership. Does anyone know the price range of a ECM flash?

[Toolman5523]

The dealership will charge you anywhere from 1 hour to 2 hours, if they try anymore than that walk. So it really depends on how much they charge per service hour. Educated guess $80 - $160.

[Nahkapohjola]

Originally Posted by chak5050

...price range of a ECM flash?

Must be 10.000$

Try Flush ? oh boy. U havent checked/read suggested linkS... Read via the links what happens with new MAF: Because all sensors are unique, each gives unique input to ECU. ECU compiles sensor readings into a datatable, collected in various driving conditions. This collection 'profile' fits just currently installed sensors... Now when new a MAF is installed, this datatable has first to be reset - zeroed - because new MAF will give different readings. This reset initiates a compensation phase - 20min or more drive - depending if u follow the "teach" pattern or not.

After MAF swap, ECU memory datatable has to be cleared, otherwise new MAF signal input will be compared against old MAF 'profile'. Reset can be done with a Nissan specific Consult or a generic tool, or by batt disconnect. ECU will lose settings after being left w/o battery for 30min or more (overnight). If the driving pattern teach up is not followed, no big deal. The data collection -phase will just be longer meaning lower performance for few hours...

[FixUrNissan]

B1 catt converter is the front flex pipe assembly. Is that the part you replaced?

[chak5050]

My car only has one cat converter. I think you're thinking about the Cali spec car.

[Nahkapohjola]

"surging/bucking issue during low RPMs" . cant be CAT .

Typical reman MAF swap-story: first three are DOA.

But. Keep on wondering wassup, don do the mentioned basics.

[chak5050]

I tried the 30+ min battery disconnect. The light is still off, but my hopes are not high. I'm pretty sure the bucking/surging issue has nothing to do with my service engine soon light.

[Nahkapohjola]

MAF will not work w/o resetting ECU, now it may. As said, theres no guarantee that current MAF is ok.

Typical problem source (70%) is connector oxidation, described in the links...
If TPS, IACV, coilpack(s) electronics fail intermittently, no evolution in sight. Only devolution. (O2 sensor is the most reliable.)