Service engine soon...
 

So yesterday morning I started the Z and the "service engine soon" light came on and the car was idle around 1000 RPM. I took it to a local auto shop and they said that I need to take it to Nissan for an "idle relearn". Has anybody had this issue? Also, I believe I still have the extended warranty through Nissan(security plus), I wonder if it'll be covered. Probably not but I thought I would ask. If it helps at all, it was giving a random misfire code (P0300). Ark Grip exhaust is the only aftermarket mod on the car. I tried to find a previous thread about this but no luck.

Thanks!

P0300 is a major pain in the ***. It seems to be the ecu's catch-all code for anything that confuses it. Assuming maintenance is up to date, plugs are good and MAF/TBs are clean, I'd clear it out with your OBD tool and see if it comes back. If it's a legit misfire, there would be another code calling out a specific cylinder.

What Chuck33079 said. Most modern cars are very good at self-diagnosis, but they're still not perfect. Hook up a code reader, check for DTCs and pending DTCs (write them down, if present), clear DTCs, see what happens.

If car is still idling high after resetting DTCs, several DIYs have been posted on idle relearn. If you can't find one using the site's search, try any web search engine and add "site:the370z.com" to your search string. The high idle makes me think the problem may be with one of the TBs - hopefully it was just a glitch and won't crop up again.

If the P0300 reappears, then it's probably time to clean MAFs and TBs, check plugs, etc (or visit a mechanic).

The FSM is an invaluable resource for trouble-shooting the 370Z. Link in my sig.

The high idle is a result of the P0300. For some reason the ECU bumps up the idle when it pops that code. Once the code is cleared the idle should go back to normal.

Thanks for clearing that up. Should make OPs job a lot easier.

Thanks to you both :tiphat:

My idle went real high last year, between 1100 and 1200 rpm. I pulled the negative battery cable for about 20 minutes and the reconnected. Idle back to normal.

I was under the impression that disconnecting the battery doesn't reset the ECU and/or clear the code/condition?

There are some capacitors in the ECM that will retain power for a little bit. If you leave the ECM unpowered for a few minutes or press on the brake pedal for a few seconds, the ECM will lose all volatile memory.

Good info.

I recall you can clear warning light/code by pulling the clock fuse on some older cars. Is there a fuse that does that for the Z or disconnecting the battery is the only way?

Not that I've read about (there is probably an ECM fuse but it will be in the IPDM which can be a PITA to get to) and no.

The easiest way to clear DTCs is to use an OBD scanner.

Quick update. Took it to Nissan and they just reset the code for me. Informed me that it looks like its nothing to be concerned with. Just a random code. After they reset it, idle returned back to normal. All good for now. Fingers crossed.

OP has the light came back on since? mine recently started doing the same thing and was told it most likely is the spark plugs.

Nope, nothing has come back on since. Looks like it really was a random P0300. Take it to Nissan and have them run it through a code reader, it could very well be your spark plugs. All they performed on mine was an "idle relearn", which is essentially just an ECU update

What if I've cleaned and repositioned throttle bodies, cleaned MAF sensors, replaced pcv valves, spark plugs and ignition coils and still have the code and high idle