have a p28 ecu with neptune rtp/demon setup that i bought from hamotorsports a few months ago. when i installed the ecu into the car and took it out for a test drive, threw a code 21. i went through all the steps via the flow chart for code 21 in the fsm and even took apart the vtec solenoid and made sure everything was clean. put it back together, took it back out for a test drive again and still got code 21.
so i took the ecu back out and put in the p06 ecu i got with the car that has been chipped by monotech. no clue what map is on it, but i did see "type r, 5 speed" etched on a corner of the cover. not sure if that's what's really on it and if it is how it would even work with my b16a. that was the last step on the flow chart, to replace ecu with a known good one. took the car out and works just fine, no cel and vtec isn't turning off.

so going by the fsm flow chart, that would most likely mean to me, that i got a bad ecu, but maybe there's something i haven't checked yet. i'm not bashing hamotorsports in any way. i bought a chipped ecu from them before and i had no problems with it. just might be one of those rare instances of a bad ecu.

so any other ideas or have i exhausted all options?

 

Call hamotorsports. Don't waste your time asking us.

 

yes i've pm'd them already thanks.

i made this thread to make sure i've covered all my bases, because i know there are people on here that are much smarter with this type of stuff than me. i can follow a flow chart and diagnose pretty good, but there might be something i haven't thought of or tried.

 

If the code only happens while the Neptune ECU is installed but is not present when using another ECU then I think your troubleshooting steps are few. Anything past that is wasted effort. Recheck the MAP you have on it and go to the Neptune forums and see if this is a common issue resolved by a simple setting.

 

Code 21 is very specific. Either your solenoid, which you say you've ruled out, or the VTEC components are to blame. Contact the vendor you purchased the ECU from. This has nothing to do with NepTune specifically.