ECU Keeps Burning D13 On PT6 Board

[H311RA151N]

Recently I got CEL's 14 which is the IACV and 6 which is ECT, engine coolant temp sensor.

I checked the coolant temp sensor's ohms and it tested to be in perfect working order. Same with the IACV.

IACV was 13.6 ohms and 11.89 volts with the ignition on ACC and engine off. So it was within spec.

Then I stumbled on this thread: http://www.cb7tuner.com/vbb/showthread.php?t=183897

So I pull the ECU out and have a look. I find D13 to be burnt.





I installed another PT6 and it burnt D13 in that one too within about 5 minutes.



I have read that D13 is for IAB's. PT3's don't have anything in the D13 spot which is what I have in the car now.

I checked to make sure the IAT and IAB plugs are not switched.

The thermostat ground is also connected, clean and secure.

The IAB wiring seems to be good. What could be causing this?

[cp[mike]]

excessive power draw through the circuit that that switch controls... either bad component (fried solenoid) or corroded wiring somewhere along the way (poor connection = high resistance = heavier draw)

disconnect the IAB solenoid and it will probably stop happening. if you replace the transistor again, you might want to replace the resistor that is next to it, too.

you might be able to find a spare matching transistor in your old ECU, somewhere else on the board.

[H311RA151N]

The wiring appears to be good so I will try changing out IAB solenoids/boxes as I have several spares. Preforming a before and after resistance test of course.

I purchased C2655 transistors and they are on their way.

However, I cannot find the resistor. I would like to replace it though. On Both PT6's.

What has me scratching my head is whether or not the false CEL's were related to a burnt D13. I guess I should just start with the IAB's and go from there.

[cp[mike]]

The wiring appears to be good so I will try changing out IAB solenoids/boxes as I have several spares. Preforming a before and after resistance test of course.

I purchased C2655 transistors and they are on their way.

However, I cannot find the resistor. I would like to replace it though. On Both PT6's.

What has me scratching my head is whether or not the false CEL's were related to a burnt D13. I guess I should just start with the IAB's and go from there.

the resistor is just any regular old 2200 ohm one. I would say pick it up from Radio Shack, but most of their stores closed. Once you have the old burnt transistor removed, you can measure the resistance across the resistor to make sure it is in spec.

http://www.radioshack.com/1-8-watt-2...istors&start=1

also, I don't think IAB generates a CEL light, does it? like leaving it disconnected shouldn't throw a CEL, but i'm not sure how it would react to a burnt transistor.

[H311RA151N]

the resistor is just any regular old 2200 ohm one. I would say pick it up from Radio Shack, but most of their stores closed. Once you have the old burnt transistor removed, you can measure the resistance across the resistor to make sure it is in spec.

http://www.radioshack.com/2-2k-ohm-1...5.html#start=3

also, I don't think IAB generates a CEL light, does it? like leaving it disconnected shouldn't throw a CEL, but i'm not sure how it would react to a burnt transistor.

I don't think that the IAB's can generate a CEL. And I know there isn't a code for IAB's or air bypass valve or anything. That's just me speculating.

Both Radio Shacks closed in the city nearest to me. It sucks. There is a TV repair shop that helps out me when they can.

2200 ohm 1/8 watt looks to be what I need.

Thanks for the assistance yet again cp[mike]! I kept trying to figure out how to identify resistors as I knew different colored stripes represented different values. That just wasn't working for me.

[NTYPE]

bro ive had the EXACT same problem.
First time i replaced the transistor and IAB worked again for like a day, then the transistor blew again

Turns out the IAB solenoid was shorted out inside (parts of the plastic were bubbling) It was still working but drawing like almost 10amps.

Replaced the Transistor (again) the board was a bit f$%ked but just cleaned it up as best i could and made sure the tracks are still intact.
Replaced the IAB Solenoid with H22A unit.

Still working to this day

Moral of the story, dont just change the transistor without figuring out why it blew in the first place.
Good Luck

[H311RA151N]

bro ive had the EXACT same problem.
First time i replaced the transistor and IAB worked again for like a day, then the transistor blew again

Turns out the IAB solenoid was shorted out inside (parts of the plastic were bubbling) It was still working but drawing like almost 10amps.

Replaced the Transistor (again) the board was a bit f$%ked but just cleaned it up as best i could and made sure the tracks are still intact.
Replaced the IAB Solenoid with H22A unit.

Still working to this day

Moral of the story, dont just change the transistor without figuring out why it blew in the first place.
Good Luck

That's really helpful to know as this doesn't seem to be a very common problem. At all. I have several IAB solenoids/boxes I can use. I will test them prior to installation and also test the one in it now. It's nice to know just what the issue is or have a close idea at the very least.

[H311RA151N]

I removed the IAB box/solenoid and tested it on a 200 Ohm scale and compared it to another IAB box/solenoid although I cannot remember where I got it at and it's a bit different style. I'm sure it's off off an H23A1 or F22A6 though.


IAB box that was on the car. 28.3 Ohms




The IAB box that I tested in comparison. 2.7 Ohms.



Mystery IAB box is smaller and cleaner and has the long vacuum lines attached. IAB box I pulled off the car is the dirtier larger one that says Honda.










Can anyone identify the mystery IAB box or verify the correct Ohms? I take it the solenoids should have a similar amount of Ohms but with them being a bit different I don't know. I really can't afford to fry anymore components. I tested the wiring and there are no signs that the wiring is faulty. Just trying to be sure here.

[cp[mike]]

your mystery box is actually the automatic intake dampener, mounted behind the passenger headlight. I have always suspected that it could be used in place of the actual IAB box, but never tried. I'm curious to hear if it works for you.

have you tried applying 12volts to it to see if the solenoid clicks open? set your multimeter to current/amp readout and hook it inline with one of the sides and see how much power gets drawn through. I'd be worried that 2.x ohms sounds very low, but then again, so does 28.x.

[H311RA151N]

your mystery box is actually the automatic intake dampener, mounted behind the passenger headlight. I have always suspected that it could be used in place of the actual IAB box, but never tried. I'm curious to hear if it works for you.

I just realized that like a minute ago and started looking through my boxes for the IAB box I have saved. I think I'm losing my mind here lately with the humidity or something is going on at least.

I guess I could try it if I don't find the IAB box I'm looking for.

[cp[mike]]

I just realized that like a minute ago and started looking through my boxes for the IAB box I have saved. I think I'm losing my mind here lately with the humidity or something is going on at least.

I guess I could try it if I don't find the IAB box I'm looking for.

i edited my last post, it seems like you didn't get to see it. might help you in your quest to try it, without actually risking the ECU.

[H311RA151N]

i edited my last post, it seems like you didn't get to see it. might help you in your quest to try it, without actually risking the ECU.

Nope, I didn't see them before but those are both great ideas. I will try that.

I did happen to find two IAB boxes I had stashed away. After playing twister for a min I got a couple pics. I suspect after the two ohms readings near 28 and the info I've found in my search that 28 Ohms is what it's supposed to be. But I don't think that really rules out the solenoid being bad...

[sonikaccord]

should be about .5 amps or 500 milliamps getting pulled through the solenoid. That's a quick calculation based on 12V and 28.3 Ohms. The solenoid is seeing about 6 watts of power. That is a very small amount of current and should not damage your ECU, at all

I'd say chances are the solenoid is good. Usually coils of wire either open or short completely...there are those weird times where it reads funny resistances, but I doubt that's the case here. I'm going to try to measure mines

If D13 has the same symbol under it as D15 and D12, then it's a Zener Diode...probably used for protection. I'm going to make an assumption here that it's probably a 15v zener diode.

[H311RA151N]

should be about .5 amps or 500 milliamps getting pulled through the solenoid. That's a quick calculation based on 12V and 28.3 Ohms. The solenoid is seeing about 6 watts of power. That is a very small amount of current and should not damage your ECU, at all

I'd say chances are the solenoid is good. Usually coils of wire either open or short completely...there are those weird times where it reads funny resistances, but I doubt that's the case here. I'm going to try to measure mines

If D13 has the same symbol under it as D15 and D12, then it's a Zener Diode...probably used for protection. I'm going to make an assumption here that it's probably a 15v zener diode.

D13 is a 68v Zener Diode.
Q13E is a C2655Y to 92L transistor.
R63 is a 2.2k 1/8 watt resistor.

So you think I may be looking for a short? somewhere? I appreciate your help. This is not my area of expertise as can be seen.

[sonikaccord]

I would say there's a short, somewhere.

Actually, if you hook your ECU up to all the harnesses and measure the resistances from all of the diode and transistor legs to ground, you may find something.

That may be tricky to understand so for clarity:
Measure each transistor leg to ground, each diode leg to ground and each resistor leg to ground. This should preferably be done with no components in the hole (or with the PT3) so that bad components won't skew your readings. This will test for shorts/abnormal resistances 'outside' of the ECU. You're trying to "see" what the transistors "sees" if you get what I mean.