Rlss

Good morning all!

New to the form, just recently bought a 98 Honda Civic Dx Manuel Transmission
Little over 100,000 miles.

I've searched Google countless hours to find out what the code P1509 actually means or is. Can anyone here please explain to me?

Little backstory- my wife was driving it one night and all of a sudden it just quit on her and would not start up again, cranked all day but no start. I automatically checked all the fuses and battery all were good, then proceeded to check for fuel, and spark also good! Once I towed it back to my house after a more through inspection I found the timing belt to be very lose and partially shredded due to a bolt being broken in half from the motor mount to the block that ended up failing inside the timing cover and shredding the belt. So ordered the new parts ( timing belt, water pump, and tensioner) put it all together made sure my TDC was perfect for both cam and crank (checked over 10 times just to be certain) after I put all together went to start it up and still had the CEL come on with just that one code. Watched countless videos and searched threads about no starts, finally I found the culprit the ignition coil was burnt out. After replacing that she started right up! So that's good, has a terrible idle issue its a fast constant surging. I cleaned the IAC and throttle body, checked for vacuum leaks, still same idle issue, went ahead and replaced the IAC valve and sensor. Thinking it had to be that since that's what the code was pointing me in. Again still same idle issue. I've read about changing the ECU but i really don't think that is the culprit in this case. What's weird is before that night my wife took the car out everything was running perfect. Any insight or help I can get would be greatly appreciated, I really don't want to throw in the towl and take it to a machanic.

*This has all been typed off my iPhone very sorry if it sounds or is butchered*

mikey1

i would start by checking the compression in all cylinders, if you had a shredded timing belt there is a very good chance you have internal engine damage/valve damage

Rlss

Thanks for the reply !

The belt was still intact just loose and shredded on one side.

Not sure how to post picture or I would.

ezone

P1509 is an IAC circuit problem, such as wiring open circuit or incorrect resistance value. The PCM is not out of the question either.

Also, the IAC valve is different for manual or automatic trans (different part numbers in the Honda catalog)

Rlss

After looking at the prices for PCMs I really hoped that's not the culprit but if so, then so be it.
I made sure I got the correct IAC valve and sensor for my Manuel transmission.

So am I looking for just the wires connected to the IAC or all of them?

ezone

The code pertains to the 3(?) wires for the IAC valve (some versions have 2 wires), the IAC valve, and PCM.
What sensor?

Rlss

Ohh I'm sorry, the sensor that is attached to the IAC valve, I have the three wire plug,

So the code is saying something is wrong with the wires for that plug?

ezone

I can't picture a sensor in my head.
Not necessarily, the code description just indicates it's an electrical related problem.

Not a performance problem like a stuck valve or idle speed too high or low.

Rlss

Yeah I replaced the part and still continues to idle up and down, so your right on that.

This is really just stumping me right now.

ezone

No not all the wires for the computer, there are only 3 wires involved in operating the valve.

Get a service manual for the car and follow what it wants you to do to diagnose this code.
You mean the electrical section of the IAC valve? The complete unit is considered one part, the electric section is electromagnet windings that make the IAC valve move.

Rlss

I have a service manual but it's saying p1509 is something different than what my scanner is telling me.

Yeah I was thinking it was a sensor.

So you think theres something going on with those three wires?

ezone

What does each one describe that code as?

Which one are you going to believe?

I can't answer that from where I sit. I just told you the description of the code in the info I have.


Engine running and warmed up: Unplug the IAC valve.
What does the engine RPM do? Raise or lower?

Rlss

Engine warmed up and unplugging IAC. Shows no difference still surges.

Rlss

My scanner says its a racv circuit malfunction for p1509

ezone

Text copied from my service information:
P1509: A problem in the idle air control (IAC) valve circuit.
That indicated to me it's an electrical issue.

Have you checked the code on a different scanner? If the scanner is not telling the truth you could chase your tail for days.
It happens, generic code readers and scanners are not always 100% accurate.


How it works:
One wire at the IAC valve is supposed to have 12v on it while the engine is running.
The other two wires at the valve are controlled by the computer, it modulates grounding on those to control the position of the rotary valve inside the IAC.


What the computer saw:
The code set because the computer saw either high or low voltage on at least one of those two wires for longer than 5 seconds.


Ohm test the valve: between first and second terminals there should be 16-28 ohms, and you should see the same reading between the second and third terminals.

Rlss

I have not checked my codes on a different scanner. Due to the idle issue not sure if its safe to drive to get it checked by a auto parts store.

I followed the service Manual Exactly to this step below:
I just Ohm tested the terminals you were talking about and indeed they were reading between 16-28 ohms, SOO in the service manual its saying to replace with a known good ECM/PCM. This is going to suck to replace

ezone

Manual trans = ECM....

It will be fine, but will be damn annoying to drive slow.
Don't go to the same place though, a different store may use a different code reader?

The next step is verifying wiring integrity between the IAC and the ECM.



Replacing a control unit is usually a last resort.....buy you might open it up and see if there are obvious burns or leaking capacitor evidence on the board.

Don't you think a bad connection could also cause this code and symptom, and the PCM could be good?

Got a buddy with an identical car you can steal/borrow a ECM from? It would be MUCH cheaper to test this way before committing to purchasing one.




If one follows a wiring diagram for the IAC valve you should be able to verify it is getting 12v to the center terminal of the connector.

Tossing the diagnostic flow chart out the window: If one follows a wiring diagram from the IAC to the ECM, you should be able to find the two wires that go to the IAC at the ECM connectors. Ohm test between those two wires and you should come up with your total IAC resistance as measured and added together previously (32-56 ohms).

I also do a 'pin drag test' to see if any of the female terminals have lost their grip, all terminals on all connectors involved in the circuits in question.

I've seen more than one case where a single terminal in a connector lost its tension and caused strange codes, no amount of parts replacing would fix it but gently wiggling the connection would make the code disappear for a short time. It's a lot harder to figure this out when it happens in a ECM connection.

Rlss

I used my buddys code reader *Acetron*

Ill pull it out and see if there is any.

Yes I do think so, Seems like its all tight though.

Unfortunately i don't.




Its not getting 12v to the center terminal.


What do you mean by 'pin drag test'?

Would i try this with the key to the on position or actually running?

ezone

Did you check this with the engine running?
If you have no 12v on the yellow/black wire with the engine running, start there. It shares power with the same color wire found on the 4 fuel injectors. There's a junction connector (splice pack) inside by the blower fan motor under the dash.

What engine does this car have? D16Y7?
Using a correctly sized male terminal to test the tension of the female terminal. If the female terminal does not grip the male pin tightly, it can't make a good connection.

Rlss

[QUOTE]Im sorry the car was not running. When tested it shows 14.26

I noticed when i unplugged the tps the surging stoped at idle but when giving it gas it seemed like it was at its rev limited. Mine does not have a tach

D16Y7

Is this something i buy? like a male terminal?

ezone

[quote=Rlss;4691547]That sounds good.
TPS has to be connected.
Yes unplugging it will stop the surge, but you can't leave it that way.

k

I have wires and terminals from many other things, old sensors and whatnot that I just can't throw away (pack rat can be handy)
I have a wide variety of harnesses I can cut up to get stuff as needed.
I also have a special tool that consists of about 10 various size electrical terminals on a keyring, but it does not cover all the different sizes used on newer cars.



This video is showing round terminals, you would need to use flat blade terminals but this should give you the idea how

Rlss

Well i checked the ECM and nothing looks burnt or out of place.

As far as pin dragging, i would have to buy the special tools for that.

I'm Kinda leaning towards new ECM, just wished i had a friend that could lend me
one =( Ill call the junkyards tomorrow and see how much they charge.

ezone i appreciate all the replys and help you have given me so far! I will certainly keep this thread up dated if i find the fix or not.

If you have any other ideas that i can try I'm all for it!

ezone

Quoting this line: Measure (ohms) your IAC valves two outer terminals and you should come up with a number equal to the total of when you measured from first and second and second and third pins.

Got a number?? Plug the IAC in again.
So....
If you unplug connector A from the ECM, find wires A13 (orange) and A14 (black/blue) and ohm test on those, what do you get? It should be the same number that you got at the valve.




If you erase the code then run the engine....Does the code reset right away, or do you have to let it run for a long time before it sets?

If a small paper clip is thinner than the terminals you need to check, you could use that.
I've even hammered paper clips flat to use as test probes so I don't damage terminals while checking as a pin drag test. There's an idea for you, but make sure the paper clip is smaller diameter or thinner/flatter than whatever you are going to check.



The voltmeter probe tips are far bigger than most of the wire terminals found in automotive connectors, so keep this in mind.

I have found in the past cases where someone tried to push their voltmeter probes all the way into wire terminals and would ruin every one of them by doing so.
Obviously, this would spread out the female terminals so far they would never touch the male terminals
(hot dog in a hallway LOL, no friction = no contact).
This is one case where checking terminal tension would find a problem.


When possible, I test and make contact through the backside of a connector where the wire passes through, and use a small paper clip as my test probe because it is much thinner than the supplied meter probes and causes little or no damage.

Rlss

*SOLVED*

Hey guys just wanted to let you know, I went ahead and purchased a ECM and recieved it today and threw in the Civic and worked like a charm! She idles smooth and after tuning accessories on the car recgonizes what do to, and no more P1509 code or any for that matter! EZONE I apperciate all the help you gave me deffently good to go through and test!!

whiteek

Did you get a used ECM or did you buy a fresh clean one?