Service Engine Soon - ECM Mode 2 - Need some help diagnosing problem.

[Camel]

Service Engine Soon - ECM Mode 2 - Need some help diagnosing problem.

Ok here is the story:

98 240sx se w/71K on the odo.Stock KA.AEM intakeApexi N1 catback exhaust + silencer.Stock manifold.Stock cat.O2 sensor replaced within the last 12 months.

Popped a "service engine soon" light when i started it up for lunch today at work. Did not have it this morning when i drove to work (approx 25 miles).

Car is running and driving as good as it ever was. The only thing that i have done recently is fill up the tank from empty with 93 oct premium and add a bottle of STP octane booster/cleaner to the full tank.

Lately (since i put on the catback) i have noticed a little bit of noise in the exhaust path. Not really backfires, but a little bit of rumbling on downshifting. Other than the normal exhaust noise. i attributed this to larger pipe diameter and no stock noise reducers like the stock exhaust had.

I searched and came up with this thread that talks about "ecm mode 2" to read the diagnostic code associated with the service light. (http://www.nissaninfiniticlub....+soon)

Here are my questions:How do I get the ecm to tell me what the code is?Could this be because of the octane booster screwing with the O2 sensor(s)?

[NISTECH]

If the light poped on imediatly upon starting it. It is not a rationality code( codes set by comparing one reading to another) your code is most likely a logic code. meaning there was a illogical voltage reading from a sensor when you started the car. A intial voltage reading was too high or too low. mode 3 is the mode where you extract codes from your ecm using the lights in the ecm. http://240sx.org/faq/index.htmlecm codes for DOHC

[Camel]

So take two aspirin and call me in the morning right? Thanks for the info, I will get back to you with my results after the weekend. And thanks again for the prompt response. (Sorry about the double post, it has been deleted in the Tech section as requested.)

C

[Camel]

So I am looking at the reference material you linked me to and i only see 2 modes and 2 conditions. Can you explain further the "mode 3" you told me about?

[NISTECH]

by those directions it is reffered to as mode 2. follow those instructions carfully and you will be able to retrieve codes from the ecm. disregard my statement of mode 3 above. I have the beniefit of a consult scan tool when I work on nissans so I really dont use the mode refference anymore.

[Camel]

Thanks, my ecu is laying in the floor board ready to be checked. Those istructions are from the 91 FSM, are they correct for the 98 also? I am assuming that they are at this point. Thanks again for all your help and prompt responses. You are a great asset to this community.

[Camel]

So i checked it but missed the first set of codes when it started flashing. Cleared the codes and they haven't come back. Maybe this was just a fluke? The code should come back if the condition still exists, right?

[NISTECH]

yea but you have OBDII which means it has to fail twice to turn the light on.

[Camel]

So just wait for the light or take it to the dealer?

[NISTECH]

wait for it. it may have been erronious. if you dont have any drivability issues just let it go for awhile.

[Camel]

The only drivability thing i have right now is a wiggle in the front end between 70 and 80mph after installing new whiteline tc rod bushings. Everything is torqued down, I think that i may just need an alignment on the car.

BTW-Nissan was going to charge me 85 dollars for the diagnostic and apply it to the price of the repair. Sound about right to you?

[NISTECH]

yea sounds like about an hour of labor. thats how we do it cept we are 95 an hour