1990 cdm dx hatch
dpfi-mpfi was running a dohc zc.
auto - manual on the dohc zc

wired it up for obd1 full d16z6 swap with a 91 si trans.

vtecfrog harness-p28

problems:

1. car WONT build heat. drove it for 10 km's and let it idle for 45 mins to an hour. wouldnt go above c. no leaks with a da rad. think the rad is keeping it too cold?

2. only code that is thrown is a 21 while the car reaches 5300 rpm. vtec and pressure switch are wired correctly but it throws the code only at 5300.... will the motor too cold throw a solenoid code?

 

Is it possible that the coolant sensor is bad?

I am sure you have checked this, but is the fan running non-stop?

Maybe the thermostat is stuck open, or you have a bad radiator cap (that would not let it build pressure, but it should still warm up some)

Can you see the coolant circulating in the radiator if you keep the cap open? If so, the thermostat is probably stuck open. (don;t open the cap when hot )

Good luck

 

sounds like the thermostat is stuck open, probably won't hit VTEC if the ECU is in open loop

 

going to swap an ef rad tonight. fan isnt running all the time, the plug off the back was lengthened and added to the thermostat housing. coolant sensor is plugged in and as far as i know operating. im going to check the solenoid itself tonight then recheck the wiring again.

 

https://honda-tech.com/zerothread?id=1812135

check this thread for code 21 help

 

radiators not your problem heating up, sounds like what s1267712 is suggesting.

 

OLD THREAD BUT DID U FIND OUT THE CODE 21 IM HAVING THIS ISSUE BUT CHECKED EVERYTHING BESIDES OIL PRESSURE BUT I JUST BUILT THIS Z6 AND JUST CLEAned the valve before i intalled it ...also most likely your car wasnt warming up due to a faulty sensor on the side of the head for ur thermo its unlikely a engine wont warm up i had the ame problem i switched the one wire sensor and that was the problem the car was actualy warmiing up the whole time i just didnt know