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woop woop!
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Discussion Starter #1 (Edited)
1992 SI w/ JDM h22a swap. Showing a CEL 22.



heres my MM ^.



Heres my VTEC pressure switch unplugged. ^

I haven't used my mm for ages and the last time I did use it was for only a few tests so I don't have much experience with these. I tried searching but nothing really covered the electrical testing for the switch as far as what I saw.

Okay, so I was reading the ecu sends a 10v signal to the switch, runs it through the switch and then back to the ecu again.

To test for the 10v:

-Which setting should I set on my MM for this test?

-Do I test the actual harness that plugs into the switch or do I test the prongs inside the switch itself? I was assuming you obviously test the harness since it's what has the wires going to it and wat has the current running through it as well, but I was reading in the FAQ on h-t and he said to test the terminals for continuity and the 2 pins for the voltage... So when I read pins I was assuming the pins in the switch itself. This is with the ignition on I'm assuming.


To Test for continuity:

-I set the MM to the setting that it is already at in the picture correct?

-Do I test the actual harness that plugs into the switch or do I test the prongs inside the switch itself? This time is with the ignition off right?

The manual says that if there is an open circuit, it will display a "1", meaning a break or discontinuity of the wires right? If theres is approx less than 40 ohms, a sound will go off, which I'm assuming means that there is continuity.

Thanks for the help guys!:)
 

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herbivore
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1,579 Posts
To test for the 10 volts, set your meter on the DC 20 setting. The connector must be plugged into the sensor/switch to get the desired reading. "Jam" the leads into the backside of the connector and turn the ignition on to get the reading.

To test for continuity, yes, you have the meter set correctly. If you are testing for continuity of the sensor/switch then it must be disconnected from the vehicle's wiring harness, then test the appropriate circuit in the sensor/switch. If you are testing for continuity of the vehicle's wiring then it must be disconnected from the sensor/switch, then test the appropriate circuit in the wiring harness.

PM me if you have anymore problems. I'm a certified mechanic.
 

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woop woop!
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3,697 Posts
Discussion Starter #3 (Edited)
Hmmm... Not sure I understand. Maybe you can help me picture this better. How come the connector needs to be plugged into the switch to check for voltage? If I have it unplugged I can check to see if voltage is being carried from the ecu through the wiring harness. So even if I "jammed" it in the back with it plugged it, I would still only be getting the voltage from the same point as if it was unplugged right?

I don't quite follow what you mean about the continuity part either.
 

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herbivore
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1,579 Posts
You can test for voltage on the circuit with the harness unplugged. I had assumed that there was supposed to be a desired voltage level created by the vtec switch, hence the need to have it plugged in. If you are just looking for a 10v signal from the ECU, then yes, all you need to reference are the appropriate terminals on the wiring harness. That'll work fine.
The continuity test is just to see if the circuit is continuous between two points. I hadn't looked at the picture close enough yesterday, but now I realize that the vtec switch only has two pins (right?). To test for continuity on the vtec switch, set the meter appropriately (like picture) and touch one lead to each of the two pins on the vtec switch itself. To test for continuity of the vtec circuit in the ECU, you woud touch one lead to each of the pins in the unplugged wiring harness.
And you are right, you don't need the ignition on for the continuity test, but you do with the voltage test.
 

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woop woop!
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3,697 Posts
Discussion Starter #5
So for the continuity test.... When I probe the 2 pins inside the switch itself, if I don't get the sound from my dmm, that would mean the switch itself has some open wire within it's circuit for that sensor right? For both voltage and continuity test, do I need to have one probe on a ground, or is that just for voltage?
 

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Premium Member
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Set the meter to V DC 20, touch the red probe to one of the wires on the dangling harness (don't remember which one is the right one, but it doesn't matter for this), then touch the black lead to chassis ground (exposed bolt on the body or the neg term on the battery). Turn the key on and see if you get something between 9 and 11 volts. If that doesn't work, touch it to the other lead on the dangling harness and try again (one is 10V from the ECU, one is the return/sense lead going back to the ECU).

To check the switch, it takes a lot more work. The problem is that you need VTEC to be engaged or to fool the switch into thinking it is by applying air pressure to the head. Neither is easy to do. Chances are it's a wiring issue and the first test will find it.
 

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woop woop!
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3,697 Posts
Discussion Starter #7
I was showing a little more than 11 volts for the harness. When I reset my ECU the cel goes away and it comes back like a day or two later. Sigh... looks like the only thing to do is just replace the switch and see if that does the trick?
 

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Make sure the other wire makes it all the way back to the ECU. Set the meter up like you have it, have a buddy hold a probe to the other lead on the harness connector, then use the other lead to find the contact at the ECU harness. I'm assuming that you did the wiring or know what pin it should be on. The meter should beep and should read something like 1.5 ohms or less.

Be careful when probing the ECU pins, don't just jam the meter probe into the cavities. You should be able to touch the metal of the right pin, though, without having to hammer it in.
 

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woop woop!
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Discussion Starter #9 (Edited)
Hm okay, thanks man. So basically probe the end at the switch and probe the other end at the ecu to check for continuity? I had blacktrax do the swap and I'm thinking there's either a break in the wire or one of the pins on the ecu is messed up. So I don't know which pin of the ecu it's plugged into.

I reset my ecu just for kicks and giggles and the cel goes away for a few days and it comes back. It's just always intermitant. I'm thinking if I did a continuity test from the switch harness to the ecu side, there will be some sort of connection but it could be poor which is why the cel only triggers sometimes. I'd prob get a false read out for that anyhow wouldn't I?

I will go ahead and test it anyway if someone could point me in the right section of the ecu, it would be great. I'll try searching on it's location on here tho anyway as I'm sure its floating around in many threads lol.

oh yah, also, would a clogged selenoid filter cause this cel to fire?

Thanks again for the help guys.
 

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Premium Member
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Take it back to Blacktrax and have them debug it. It's obviously intermittent and probably beyond what we can help you diagnose via posts on a web board...

A clogged solenoid could cause this, but it would cause failure of VTEC to engage which should be pretty noticeable. So would a bad switch.
 

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woop woop!
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3,697 Posts
Discussion Starter #11
Yah VTEC does fail to engage sometimes even when the CEL isn't on. I will give nat a call at blacktrax I suppose.
 

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Sorry to jump in this thread but if the VTech isn’t working does it just not run? Mine hits those RPMs and it cuts out like its hitting a rev limiter.
 
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