Secondary Throttle Valve Actuator Defect

[D_Klein]

Last Friday I was disappointed to see a red light illuminate on my instrument cluster, along with an "F1" indication where the coolant temperature is displayed. The bike has a user diagnostic mode which can be activated by the following procedure:

1) Remove the seat and rear frame cover (rear fairing)
2) Find the 6-pin connector with a white, rubber cover near the relays
3) Start the bike (or turn the key to the accessory position if the bike will not start)
4) Jump the two terminals as shown in the picture below
5) Write down the error code as displayed in the coolant temperature display (WRITE IT DOWN, the code may not always remain stored after retreival).



In my case, the code that came up was C-28, or Secondary Throttle Valve Actuator (SVTA). After testing the actuator per the shop manual, I concluded that the actuator was defective.

The first thing I did was call the Suzuki dealership, who told me that this part was ONLY available as a full throttle body assembly - $800. No doubt this infuriated me. Why do I need a whole throttle body assembly for one electronic part?

After further investigation, I came to find out that this part failed often on the '04-'05 inline fours, due to an incredibly poor design that left solder points on the actuator motor electrical connector incredibly vulnerable to separation by means of vibration.

First and foremost, the SVTA is an emissions part. Some of the reading that I did on the matter alleged that emissions parts are to be warrantied by the manufacturer for 5-10 years, but I wouldn't expect every dealer to honor that request. Some guys paid up to $2000 to have their throttle body housing replaced along with the SVTA to get the problem fixed.

I tore mine apart and fixed it myself. Here are the steps required to fix the SVTA that will not only save you boatloads of time and money, but also give you the satisfaction of fixing it yourself.

Items needed:
- Drill or drill press
- (5) M3x12 screws
- (5) M3 nuts
- Soldering iron & solder
- Security Torx bits
- Multimeter

The STVA is located on the right side of the throttle body housing.

To test:
1) Remove seat
2) Lift & support fuel tank
3) Remove airbox cover
4) Turn ignition switch on; the secondary throttle valves should cycle all the way open, then close very slightly to 95% open. If the valves close, proceed to step 5.
5) Use contact cleaner to clean the STVA connector.
6) Reconnect SVTA and repeat step 4. If results are the same, proceed to step 7.
7) Test for resistance between the top two terminals and bottom two terminals. Shown below as viewed while unit is installed on bike, from rider position. Resistance should be approx. 7-8 ohms. If the unit tests bad, proceed to unit repair (below).



To repair:
1) Remove seat
2) Lift & support fuel tank
3) Match-mark position of Secondary Throttle Position Sensor (if not already done so by the factory)
4) Remove Secondary Throttle Position Sensor using security torx bit
5) Remove STVA (CAUTION: these screws can strip easily, so have an impact driver handy if necessary)
6) Drill out the rivets that hold the two halves of the STVA enclosure together
7) Carefully pull the two halves apart



8- Thread one of the M3 screws into the back side of the actuator motor to pull it out of the housing (rubber pads help keep the motor held in place. Removing the motor by hand may cause damage to the connecting parts)
9) Inspect the solder joints, particularly those circled in red below (those are the joints most prone to failure due to the part design).



10) If possible, remove all old solder from any broken joints.
11) Place motor/connector assembly into actuator housing to temporarily locate the components
12) Re-solder the four joints
13) Test the resistance between the terminal pairs as described in step 7 (testing) above.
14) Reassemble the unit, using the M3 screws in place of the original rivets (blue threadlocker is recommended)
15) When facing the right side of the bike, use a flat-blade screwdriver to rotate the STVA keyway all the way counter-clockwise.
16) Install the STVA
17) Manually open the Secondary Throttle Valves (clockwise when looking at the right side of the bike)
18- Install the Secondary Throttle Position Sensor (STPS), but leave the mounting screw finger-tight
19) Manually check the operation of the Secondary Throttle Valves. If they do not open, then you have the STPS aligned improperly. Proper alignment may take several attempts, but this is an important step.
20) Align the match-marked STPS and fasten its mounting screw
21) Turn ignition to ON position and test as described in the testing section (At this point, your red light should no longer be illuminated if the unit has been properly repaired)
22) Install airbox cover
23) Lower & fasten fuel tank
24) Install seat

If you don't feel confident doing this kind of repair yourself, feel free to PM me. I'd be glad to fix it for you for a modest fee.

[Motorcycle Forum]

[Blade]

Very nice write up.

[Clint]

Great writeup. Sucky photos. I bet you haven't read that manual.

I'd bet if you put this on a dedicated web site you'd have good traffic. That's some great info.

[themeatmanlandry]

Nice write-up! Hope I never need it.

[D_Klein]

Great writeup. Sucky photos. I bet you haven't read that manual.

I'd bet if you put this on a dedicated web site you'd have good traffic. That's some great info.

I was too impatient to upload my own photos, so I modified some that I found elsewhere.

I'm not too surprised that no one at the Stealership knew what the hell the part even was.

[intimid8er]

Damn D. The work you've been doing lately (self-taught for new readers) is not only downright impressive, it's highly commendable! Good job!

[D_Klein]

Thank you sir! Motorcycles are newer to me, but I've been able to apply my mechanical aptitude and automotive knowledge. Plus, the satisfaction of fixing something yourself is well worth the effort and possible risk of doing something new. Like I always say, any repair is possible with tools and a manual.

[IrocRob]

Thanks for the write up on this problem. This information helped me fix
a customers bike for much less money than I would have managed without
this thread. I don't think it would have occurred to me to disassemble the
motor unit and take a look inside, I would have gone directly to "replace the unit"...Well Done!

[D_Klein]

Mission accomplished! That's why I posted. Thanks for the praise.

[Gixxerman]

Mission accomplished! That's why I posted. Thanks for the praise.

Gee, now he's famous too Nice work bro

So you didn't buy the Special Suzuki Tool for the service plug (6-pin) ? You'll get five ***** just for not doing that

[D_Klein]

Gee, now he's famous too Nice work bro

So you didn't buy the Special Suzuki Tool for the service plug (6-pin) ? You'll get five ***** just for not doing that

HA! I'm sure Suzuki wants to sell me a fancy paperclip for $20, but I just ain't falling for it.

[Gixxerman]

You DON'T want to know how much it costs in my country. I work at a zuki dealer so I do use it, but I wouldn't buy it when everyone knows you don't need it.

Special tool, uhm *giggle*

[TheGeek]

Just so you know where this info came from, it's my knowlege and information. I posed this fix on "the other site", and I'm providing 2 pics as proof. This is my work! Passing it off as your own.... not cool.

These 2 were taken at the same time on MY workbench 6-2007.

[TheGeek]

Now that I think about it... maybe I should be getting a kickback from the ones you've fixed.... 20% sounds fair to me!

[TheGeek]

Wow...even messed up the details!

Don't use any old M3 screw. I spent about an hour at Lowe's trying to find a perfect fit. Rust and vibration are also concerns. Use #6-32 half inch stainless steel machine screws and secure them using nylock nuts.

You don't need the tamper proof torx unless you can't get it back on the shaft. And if you do have to remove the STPS from the STVA, when you put it back on, the test value in the manual is wrong. It's 1.6kOhms, not 0.6kOhms.