MIL Code 29

So using the great information off this forum I was able to manually read the MIL code on my 2010 NT700, 26k miles. I know the code 29 is the IACV malfunction. Normally does this meaning replacing the motor assembly, part # 16430-MEW-921? OR cleaning the unit? By the way the problem I am having is intermittent stalls at idle at red lights or when very slow coast.

Can anyone provide info about this code, replacing or cleaning IACV?

Thanks Matt

Are you getting the code 29 consistently or is it coming in intermittently? For troubleshooting, it's better to be getting the fault code consistently.

The best I can understand is that the code 29 is sensed by a loss, or reduction in voltage from the IACV. So it senses an electrical fault, and it may not be able to sense a blockage fault in the air of the valve.

The shop manual has 4 basic steps for troubleshooting a Code 29
- check wiring and connectors at the IACV and the ECM. There is also another 10 pin connector between the throttle body and the ECM that could cause problems. Follow the wiring from the IACV back toward the ECM and you will find it under the air filter housing.
- Check for shorts to ground at the IACV connector.
- Check for continuity from teh IACV connector back to the ECM
- Check winding resistances of the IACV. 99-121 ohms.

If it were my NT, I would:
Buy the IACV from a dealer with a good return policy and don't open the package unless needed. The connector to the IACV (and ECM and the other 10 pin connecor) is as suspect as any other component and in that case you wouldn't need to replace the IACV. Check the IACV connectors and see if it is fully connected. Disconnect, clean, and reconnect it. If you think the connector was loose or dirty or corrosion was causing the problem, put it all back together and try it out. It everything seemed normal, remove the IACV and clean it and look to see if something was keeping it from rotating. If you find something, put it back together and try it out. If you don't find anything yet, do those electrical checks to further troubleshoot it. Replace the IACV if it fails the the winding resistance checks.

I don't remember anyone reported a IACV fault before. Keep us informed of what you find.

Dan, you are one of the great resources on this Forum -- thanks for sharing your knowledge! Don't know what we'd do without you.

As I have mentioned on another thread, the NT can log false sensor codes if the charging system is not 100%.
Reg/rec problems are relatively common.
IACV problems are not.
If you are getting code 29 (voltage loss) I would be looking at the charging system and battery first.
If the battery is weak the voltage when cranking will drop very low and this may cause the ECU to think that a sensor voltage is low.
As Dan says, if it is a consistant code it is more likely to be a sensor or related wiring problem.
If it is intermittant it may be a low supply problem.

Macka

I agree that a low voltage due to regulator or battery problems could cause some random low voltage codes at times. But if it is an actual low voltage condition there should be some other indication to support the low volts...... dim headlight, laboring starting motor, dropping out grip heater (if installed), or measured low voltage.

With the OP describing the code 29 for IACV, and then adds that he is experiencing stalls at idle, that supports an actual IACV problem. But with electronics operating in wet environments that sometimes get dropped and crash, nothing is ruled out completely.

I agree that it is MOST likely to be an IACV problem given the symptoms.
Just keep in mind that none of us have ever heard of such a problem on the NT as far as I know and the bike is not that old.
There is always a first time though.
Given the speed with which the ECU processes data it only needs a low voltage for a few milliseconds to record a fault.
A weak battery can drop to a low voltage on the initial engagement of the stater (maximum load and) then recover and seem to crank reasonably well.
A similar thing is a known problem on V6 Toyotas for example. They will crank over normally due to a reduction drive starter which only draws less than 100 amps but will not start. This is because the voltage of the weak battery drops below 9 volts and the ECU will not switch on the injector circuit. Use jumper leads and it starts instantly but cranks at the same speed. The inexperienced can waste time trying to figure out why the injector circuit is malfunctioning when it is simply low supply voltage to the ECU. I have seen this situation myself several times. This is just an example to show how deceptive symptoms can be.
Good luck Matt.

Macka

IACV problems on Honda's are very rare. Does the MIL light stay on all the time? The EFI system on the NT700 is pretty basic, it is similar to the systems found on pre-1996 cars sold in the USA (before OBD-II). I did a lot of driveability diagnosis when working as a tech, and these older systems didn't set a code unless they saw an electrical fault, usually a short or open.

If the MIL is on all the time, start by checking the wiring from the ECM to the IACV. Make sure there is no damage to the wires from mice, or chafing, check for exposed wire. If you have access to a meter you can check resistance at the IACV itself. Spec is 99 to 121 ohms between pins 1 and 4, and again at pins 2 and 3.

Interested to find out what it is.

Brad

Made my way down to the IACV and removed it. Someone mentioned to leave it connected to the harness and turn the ignition key on to see if it spins. Turned the key on and it did spin but I noticed that the small cam that is threaded onto the shaft was loose. So I removed the IACV and turned the cam by hand in both directs and confirmed that it did spin on the shaft. When turning the cam clockwise by hand it actually unscrewed off the shaft. Turning it counter clockwise by hand the cam tightened down all the way then the motor would begin to spin.

This does not sound right to me, any info would be helpful. Thanks Matt

It does not sound correct to me BUT I also have no experience with an IACV.

I am wondering if there is a lock nut missing or maybe some locking paint missing from the thread which then allows it to turn.

Seagrass

The manual page 6-63 describes the "slide valve" screwing onto the stepper motor shaft but it says clockwise to seat it on the stepper motor not CCW.

Brad

I never mind revealing my ignorance.

What is an IACV?

Idle Air Control Valve (I had to Google it too)

Seagrass

I think that you will find that the loose cam is correct.
That is how it works, by moving up and down the shaft as the motor spins one way or the other it regulates the airflow.
Some IACVs have a "pintle" or cone fixed to the end of the shaft that moves in or out (like a needle and seat), some are like what you have described and the shaft rotates and the pintle moves up and down the shaft.
If it is a screw thread up the length of the shaft it will be the latter type. On the former type the pintle/cone/cap is NOT removable.
I am not certain what the NT uses as I have not taken one out.
If the motor spins for a second or two and then stops with ignition on the chances are that it is OK.
That is the ECU setting up the IACV for the next start.
You have probably noticed that even with a hot start the engine idles above normal (hot) idle speed for a very brief time after each start.
That is the IACV in the "start" position but it is very quickly pulled back by the ECU to the hot idle position when the ECU looks at the coolant temperature.
If it did not do that you would have starting difficulties in hot weather due to remaining fuel vapour in the inlet ports causing an overrich mixture.
When you refit the IACV it is important that the "cap" or pintle is screwed all the way up to the top of the thread otherwise the IACV may be damaged when you bolt the motor back in by jamming on the seat and "stalling" the motor. The ECU will reset the base position when you turn the key on.
If it does not and the engine idles much too fast on start-up just turn it off and restart a couple of times and it should fix itself.

Macka

To add to Macka's reply:

If you do end up replacing the IACV valve assembly, the engine will idle high on the next re-start. Don't be alarmed, the ECM will recognize this and bring the idle down to the proper rpm based on the coolant temp and crank sensor inputs.

Brad

Brad, do you have a book number of the manual you are referring to? I have a service manual I downloaded from the UK web site and on pg-6-63 it discusses the air cleaner. Is there more than one service manual? This is the book number I have, took it from the table of contents page. (Paper Book Part No. 62MEW00)

Thanks

I have the USA service manual, 61MEW00, the procedure is on pages 6-63 through 6-64. It states turn the slide valve clockwise until it's lightly seated in the stepper motor, then apply a light film of oil to the valve and o-ring. Install the valve, aligning the groove on the valve with the pin on the housing.

My words now: if the groove doesn't line up turn the slide valve counterclockwise (the idea here is to not jam the threads) until the groove aligns, this should not be more than 1 turn. Carefully push the stepper motor into the housing (the slide valve should not bottom out), then install the holding plate and the 2 torx screws.

Once it's back together and you start it, this is where it will idle high. You'll know it's working if the rpm drops as the ECM commands the slide valve inwards. Your code 29 should be gone too.

Let me know if you need any more help.

Brad

Yes the manual # I have is 61MEW00 also.

The other Brad

So it's been several months and a new IACV and the bike has the same symptoms. At first I thought I had it corrected because it took several weeks for the intermittent problem to occur. Below is what happens, notice that this happens 98% of the time with less than 1/2 tank of gas, warm weather, temperature gauge at 1/2. Normally the bike runs between 1/4 and 1/2 on temp gauge unless I'm not moving in traffic, then it will go to half or a hair above. Full tank and cool weather it very rarely happens.

Here is my problem, I get a bogging at 2800-3k rpm. Please realize this is not from being in 3rd gear at 20 mph and trying increase the throttle. If I pull in the clutch and rev it several times it will smooth out. The other problem is that it stalls once in a while at a red light. The 2 problems seem to co-inside with each other. I have NO MIL codes logged.

Anyone have any suggestions on how I can trouble shoot this problem? Could it be a fuel pump problem?

This is a 2010 NT with 26k on it, had 24k mile service done on it 2yrs ago with 22k on it.

Thanks Matt

Have you had the spark plug caps replaced? This was a common problem on the 2010 model NT700 and it could be the cause of your symptoms.

Seagrass

Spark plug caps sound like the usual suspect. Cheap too. Here is a copy of the service bulletin. Try that and let us know if the problem persist.

dnktng said:

Have you replaced the spark plug caps?

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