monzster

I have a 90 CRX SI with a B16 swap. I have had the car 12 years and have never had an issue until this week. I was driving and went in to VTEC but it didn’t engage instead the check engine light came on. Car drives ok other than that. I checked the code and its 21 : VTEC solenoid. I performed the test per an OE manual and it says that the ECU needs replacing. Basically this test is checking the ohms on the solenoid and checking the harness for continuity and for a ground short which both are ok. I don’t know too much about ECUs so I am assuming, and, this is what I am trying to verify. That the ECU is ground and it sends a 12 volt signal to the solenoid. I did run 12 volts for just a fraction of a second to the solenoid and it does click. I also connected a volt meter to the harness at the solenoid and when the ignition is turned on I have 2.7 volts and when the car is driven thru the RPM band to 8,000 it stays at 2.7. If it is agreed that the ECU is bad has anyone ever used someone to rebuild one. I see that there are companies that do this per Google and EBAY but are not sure with going this route. The part number on the computer is 37820-P30-000. Autozone can get me a P28 Cardone reman for $450. I’m just trying to find some options because the dealer says they are no longer available. Thanks for any help in advance.

motoxxxman

The 2.7volt output is normal, that's how the ecu tests to see if the solenoid is good. I doubt the ecu is bad if it's putting out that 2.7volts and is able to store a code 21. There are lots of places to buy ecu's for much cheaper if you ever needed one, but I highly doubt yours is bad.
My guess is you simply have a bad connection somewhere, most likely at the connector for the solenoid. If the ecu detects a fault with the solenoid for whatever reason and throws a code, it will disable vtec. So until the code is cleared, it will not attempt to engage vtec.

Disconnect the battery, plug the vtec solenoid back in, do not connect a voltmeter, plug the battery back in, and take it for another drive. See if the problem comes back. Report back what happens after doing this

7rrivera7

iTrader: (1)

If you have a friend with a similar car/engine you can run your ECU in his car to see if VTEC activates.

PM me for repair or replacement...

monzster

Motoxxxman I did as you suggested and the problem still persists. I am going to recheck all the connections again and perform the the test again per the manual again just make sure I have everything in order. I didnt have time to do that yesterday but will let you know if I find anything different. 7rrivera7 unfortunately I dont know of anyone but will keep that in thought until I can figure out the issue. Thanks for the input.

monzster

So I disconnected the battery and hooked it back up. Took it for a test drive and still same issue. I rechecked the resistance on the solenoid and it is within specs. I checked continuity on the wire going from the solenoid harness to the ECU and it is ok. I connected the harness to the solenoid and back probed the connector for the solenoid and checked it at the ECU and it is ok. So my next question is the solenoid suppose to receive a 12 volt signal from the ECU to activate it. If so can I run a wire from the battery and run a different wire to the solenoid and have someone sit in the passenger seat and connect the 2 while I am in the higher RPM range to verify that it is in fact working. Will this work for testing purposes. Thanks again.

monzster

So I wired a push button switch from the battery to the solenoid and the VTEC is in fact working when I apply 12 volts. I reconnected the solenoid to the harness and back probed it and am only getting 2.7 volts at all times so I am going to say its an ECU issue. I guess I could remove the pin at the ECU for the wire that goes to the solenoid and connect the push button switch to it to see if VTEC works but dont think that is really necessary being as I have continuity on that wire.

motoxxxman

the problem with using a button is that the engine requires very different amounts of fuel and timing in and out of vtec. If the ecu isn't commanding vtec, it will run extremely lean and too much timing when you push the button.

It does sound like an ecu issue, though I can't imagine why it's throwing a code 21 if there's an issue with the ecu. Only suggestion I could make is see if you can borrow a known good working ecu and give that a try

monzster

Im not on running a button constantly. I just wanted to verify that the VTEC part was actually working. I have been driving the car cause it kind of my daily at the moment being as my sons car is broken down and he has been using my Ridgeline. I contacted a company that a friend of a friend was telling me about called phearable to see if they would rebuild my ECU but they dont rebuild anymore but the guy that emailed me back said that he had a hard time believing that it was an ECU also so tonight I rechecked everything a third time even rechecking my solder joints and everything has total continuity thru the whole harness from every connection. Phearable has a chipped ECU for just bolt on's for $230.00 which is basically all I have. I thought this was pretty decent price being as used P30s are going for 300 - 400 on EBAY. Just curious has anyone dealt with them. Or has anyone had any dealings with any other companies. Again I really appreciate all the help.

7rrivera7

iTrader: (1)

If your current ECU is chipped, you can transfer the basemap from your old ECU to the new one.

holmesnmanny

backprobe the power lead on the solenoid with a tpin with a test light that you can see while driving, clear the code, drive to vtec, see if the light lights up

and that part number isn't coming up as valid, check it again

monzster

7rrivera7 my old ECU is not chipped (that I know of). When I did the engine swap I bought everything as a package and the person I got it from is no longer around. Holmesnmanny I did that with a volt meter and am only getting 2.3 volts to the solenoid at all times when the ignition is turned on, the car running and thru the whole RPM band, so it would not light a 12 volt test light. I rechecked the part number on the ECU and it is what I posted previously. To my understanding the ECU is a JDM one.

JRCivic1

Sounds like the ECU may be bad. Have you tried to replace it with a known good ECU and taken the car down the road to see if VTEC works ???

motoxxxman

Was the voltmeter showing 2.7v while it was connected to the solenoid? or only when the solenoid was unplugged?
What do you get for a resistance value when testing between solenoid plug wire and anywhere on the engine?

As for a chipped ecu, NEVER treat a basemap like a full tune or stock ecu. While sometimes a basemap can work great, most times it does not and will often damage the motor if driven on for an extended period of time. If you buy a chipped ecu, you will NEED to get it tuned by an actual tuner. Food for thought.

Phearable and Xenocron are both reputable companies to buy chipped ecu's from.

monzster

JRCivic1 I dont know anyone that I can swap with. Motoxxxman the solenoid was plugged in and I was backprobing it at the solenoid end when I had the the 2.7 volts. I also tested it unplugged at the harness side and had the same voltage. This is when the ignition is turned on and also with the car running and thru the whole RPM band. The resistance at the solenoid unplugged is 18. Per Honda it is ok between 14-30, I did not realize that a chipped ECU had to be tuned. I assumed that it was plug and play. Thanks for that information. I guess if I go that route then I better get some what of an estimate on what that will cost to tune it. Fortunately there is a guy in my area that can do that.

motoxxxman

Hmm, ok I guess I misinterpreted what you said earlier on. Thank you for clarifying. This info is very odd and almost doesn't make sense. It sounds like you have a couple issues going on.
Here's what should happen:
1) testing voltage at solenoid wire (harness side, not the ground wire):
...1a: with solenoid unplugged: ignition off should show dead zero. ignition on should have anything from 2.5-12 volts (different ecu's put out different voltages). Most common is around 11 volts though.
...1b: with solenoid plugged in, clear the trouble codes by removing the battery neg wire for 30 seconds, then install it again and turn the key on. should have dead zero volts. If you get any voltage at all with key on engine off, either the solenoid is bad, or the solenoid is not grounding properly, or the trigger wire is not making a good connection with the solenoid, or the ecu is bad.
2a) unbolt the solenoid trigger wire. test resistance between trigger wire and base of vtec solenoid. 14-30 ohms is good.
2b) test resistance between trigger wire and anywhere on the actual engine. resistance should be the same as 2a, or darn close, within 1 ohm of 2a. If it's different, it's not grounding properly for whatever reason.
3) test resistance between the solenoid trigger wire (harness plug) and the ecu pin A4. Should be zero ohms. Anything above 0.5 is usually a sign of a weak connection or break in the wire somewhere

monzster

Mottoxxxman my solenoid does not have a ground wire. It is a single wire from the solenoid to from the ECU. My solenoid is grounded to the engine. Are you talking about the pressure switch?

motoxxxman

yeah I had a brain fart there. realized it while I was at work today haha, sorry.
I edited my above post, re-read it

monzster

Ill run your test to see how things turn out and let you know what I come up with. Probably going to be the end of the week. Thanks.

monzster

Mottoxxxman per your instructions this is what I got
1A - voltage is 0 with ignition off. voltage is 2.6 with ignition on
1B - voltage is 0 with key on engine off
2A - ohms 15.3
3 - ohms 0
2B - I am confused on this one. You said resistance should be same as 2a. I have always checked resistance in ohms. So I wasnt sure if you wanted AMPs. I also didnt know if you wanted the key on or off. So this is what I did. If wrong let me know.
With the key off the ohms are 10.7 and 0 amps
With the key on the ohms are 2.5 and 1.1 milliamps.
When doing this test per the OE Repair manual it states to do this with the key off if there is no continuity to replace the ECU and if there is continuity to repair the wire between the ECU and connector. I have triple checked the continuity on this wire 3 times including the last time checking it from each connection point individually and it has continuity at each point as well as from the ECU to connector. Being as I have 10.7 ohms instead of 0 I'm thinking the ECU is the culprit, per the manual anyway but then again if I have continuity it says to repair the wire. Am I correct in thinking this? I get so confused with this wiring stuff. Again Thanks.

motoxxxman

for 2b I meant to test resistance (ohms) between solenoid trigger wire (on the solenoid, unplugged) and somewhere on the engine. basically the same test as 2a, but using somewhere else on the engine for the ground probe instead of the actual solenoid base.

Also, it's extremely rare for the ecu to die. But it does almost sound like the ecu might be bad.

Do you know anybody else with a b16 that you could test your ecu in their car? or their ecu in your car?

monzster

Unfortunately I do not. I did find one on Ebay. Exact matching part numbers. I snatched it up for under 200.00. So I will find out. Will be in next week sometime. I'll keep you posted. Thanks again for the help.

motoxxxman

you're welcome. Hopefully that solves it.

holmesnmanny

code 21 issues could be related to the hardware, if the new ecu doesn't fix it you should take a look at the hardware assembly, see if one of the cylinders is different mechanically from the other 3, look for a problem

motoxxxman

uh, what? I know you're pretty wise, seeing you post fairly often. But how would the mechanics of anything be related to a code 21? The code 21 is only for a fault in the solenoid system electronically, not mechanically.

monzster

Sorry its taken so long but there was a delay in the ECU shipping. I just got it in and it did solve the problem. I once again want to thank everyone for the help. Its nice to have VTEC back. Its been a pain in the butt learning experience but thats how we learn, LOL