[Sportedge]

Guys, I'm still dealing with my ASC light. Sometimes on as soon as the care moves, sometimes on as soon as I sudently step on the gas. Once lit, does not clear unless I stop the engine. I found code 102: Throttle valve actuator mechanically faulty. Now that makes sense. How do I go and conduct any kind of test?

 

[NZ00Z3]

Your 4 cylinder Z3 will have an Auxiliary Throttle Body (ADS) housing with a position sensor and a separate ADS actuator.

The ADS body is the first unit after the MAF. There is a Bowden cable between the body and the actuator.

Check the electrical connections to both the actuator and the position sensor are clean and tight.

Disconnect the Bowden cable and check that it is moving freely.

Check that the Bowden cable is moving the ADS butterfly.

Hope this helps

 

[Sportedge]

Already checked for cleanliness. Will do the rest first thing tonight after work. Thanks

 

[Sportedge]

NZ00Z3, it did not help, but it sure provided a ton of hope! Both connectors were spotless, and the cable was free to move within the sleeve. Throught the small door, on the side of the actuator, I was able to move the gear that pulls the cable: it was smooth with no missing teeth or any debris indicating any form of wear. The spring inside the actuator saw that the gear returned to its original place.
When I start the car, the ASC light is always off (its on for the time it does the self test). With the light off, it turned immediately on as soon as I disconnected the actuator. Stop the car, plug the actuator back, restart (light off), then unplug the ASC position sensor only to see the light come on again.
I dont know what to make of that, since the code said: 102-throttle valve actuator mechanically faulty. Plus, that code or that description of it is not even listed in the Bentley manual...
That ASC light on is really getting at me, plus the fact that the car has started missing, as if the fuel pump was dying on me. But it could be misfire since I noticed a small backfire between two shifts. But no check engine light on. Yet. Any other ideas on that light or on that code?

 

[vintage42]

... the car has started missing, as if the fuel pump was dying...

Is that at idle, or full throttle, or just driving along? Is missing a symptom of a fuel pump? Do fuel pumps grow weak gradually, or stop suddenly?

 

[Sportedge]

It's under load. The more you ask for, the more it misses. Base on my personnal experience on other brand car, if the pressure from the pump is slightly under, it will do that. Mind you, it could be the fuel regulator reacting to the low pressure, or the injectors not being able to spray in a correct pattern. That, I can't tell for sure. I also know for sure, on other brand, that fuel starvation will sometimes cause an engine to miss.
Sometimes, the fuel pump will just die. End of story. On other times, it will gradually go weak, sometimes less noticeable on a full tank, where the pump is cooled by the fuel itself, and sometimes more noticeable on an empty tank where it will get too hot.
On a different story, I finally ordered the Supersprint muffler I told you about, for $150.00. You were right: it was missing a number. The correct number is 785705.

 

[NZ00Z3]

When was the fuel filter last changed? Lack of fuel could relate to pressure (pump) or flow (filter/blockages).

 

[Sportedge]

It was replaced 3 years ago, or in my case, 7000 miles ago.
Do you have any other suggestions on code 102-throttle valve actuator mechanically faulty? My Bentley manual does not say anything on that code or that definition. Anything else I was able to find on the internet applies to much newer BMW models and I can't relate on any of it.

 

[NZ00Z3]

Been thinking about how to test the actuator?

Bentley shows it as a simple 2 terminal motor. One polarity will drive the throttle butterfly closed. I'm picking that the other will drive it open again, so try applying 12V DC to the two terminals and see if it works. Try both polarities.

Not sure how smart the module is with its system monitoring?
- is it monitoring the actuator for a resistance and flags the fault code when the resistance is too high/low?
- Is it putting a test pulse on the actuator and looking for movement in the position sensor?

Test the resistance of the actuator motor, it should be low, less than 5 ohms.

 

[Sportedge]

Hi, I was kind of waiting for you...
The motor is isolated. For it to work, it would need a + and a -. I took the actuator off and got to play with it a bit. The inside gear is spring loaded. When voltage is applied, the motor goes and retracts the cable, thus forcing the butterfly to close. When there is no voltage, both spring from the ASC throttle body and the one inside the actuator pulls the Bowden cable back to its initial position. This is not a fact, only my theory. I do not have my Bentley manual handy right now, but from what I recall, the power to the actuator is coming from a module. Are'nt all electronic modules working on +5vdc?
But that motor has to do quite some work to close that butterfly. It's most certainly 12v, but I dont want to fry something, unless you know for sure that it is really 12v.
Both suggestion about the resistance and the pulse test are excellent. I'm going right away outside to do some tests. Checking the resistance will take 2 minutes. As for the pulse test, the more I think of it, the more I think you are right. The Bowden cable is held in place by a bracket. It's actually running through the bracket. But the plastic connector that secure the cable to the bracket is broken. If it pulls the cable 1 or 2 mm for a pulse test, I'm thinking that maybe the sleeve of the cable retracts, but not the cable itself, therefore, no movement picked up by the sensor. This is going to be very fun. I'll let you know what happens later. Thanks.

 

[Sportedge]

The resistance is 6.9 ohms
At least, I know now that the motor winding is not open.
I remember reading somewhere from a guy who totally deleted the whole ASC circuit, and in order to fool the computer into thinking that the actuator was still there, he welded a 10 ohms, 1watt resistor across the end of the male connector (that used to connect to the actuator).
You are saying less than 5 ohms, he went for 10 ohms, and my tester shows 6.9 ohms. Another tester would probably show a slight difference, meaning I might not be exactly at 6.9
I'm tend to think that my actuator is good. Might be drawing a fraction of an amp. more, might be running a fraction of a degree hotter, but I think it should be able to work.
I managed to secure the sleeve of the cable to the bracket. I will take her out for a spin later, hoping the ASC light will stay off.

 

[Sportedge]

I went for a long drive. I drove like an old lady, except I did not hit anything...The ASC light did not come on at all. On my way back, I laid two rubber track on the asphalt. The ASC light flickered, as expected, and went off right after! I thought I was living a dream! It was now ok! I played with the ASC button, the light went on and off and on... It was working!!!Drove back home. Encountered a stop, then a red light. And it came back on. I was crushed. I shut the engine on and off several times to clear the light, but it always came back on. Sometimes right away, sometimes after the car rolled a bit, sometimes after 2-3 minutes of driving. When I got back in my driveway, I tested the resistance of the actuator once more. It was now up to 8.1 ohms!!!
Could it be the brake switch? What causes the actuator to kick in except if the computer monitors a speed difference between the front wheels and the rear wheels??? And it's actually only the light that comes on. There's no loss of power. Only that light, as if there was a bad relay somewhere...
Tomorrow, I will disconnect the actuator and install a resistance of a value less than 5 ohms to the end of the actuator plug. See what it does

 

[NZ00Z3]

My 5 ohms was a guess based on the fuse supplying the fuse in the drawing being 5A.

Lets do a bit of math. I= V/R
- for the 6.9 ohm resistance that is 12/6.9 = 1.7 A
- for the 8.1 ohm resistance that is 12/8.1 = 1.5 A
- for a 10 ohm resistance that is 12/10 = 1.2 A

These sound about right for a small 20 W motorized actuator. A 5V DC supply would more than 1/2 the current and the power to drive the mechanical parts. The wires are 2.5 square mm, so are designed for a bit of power.

Copper has a positive temp co-efficient, means the resistance of the coil will increase with temp. So the change in coil resistance from cold to hot car (say 20 C to 70 C ambient under the hood) is not a worry.

5 V DC may be used for some of the data bus communication. When BMW drives any device, relay, motor etc they use 12 V DC in order to get sufficient power with lower current and hence smaller wire. Check the voltage used by connecting your volt meter in place of the actuator and turning the car on. See what voltage the test pulse is. May have to use hold or delta function on a digital multi meter.

If 10 ohms is the dummy value for the actuator, then I suggest that you look at the other end of the wires. Do your resistance tests at the ABS/ASC module looking back towards the actuator, connector x1652, pins 1 and 3. For the 1996-1998 Z3's, Bentley says the module is behind the glove compartment. Is the resistance higher than 10 ohms? A loose/corroded connector?

Is the end connector on the Bowden cable still secure?

There is a bit of a time difference between us, You're in Canada and I'm in New Zealand. Friday night here and I will be heading out to a dinner party soon, then the weekend

Hope this helps,

Regards

Muzz

 

[Sportedge]

Yesterday,I did check voltage at the connector while the engine was running and the ASC light was on. I had 2.xx vdc from positive to negative, and give or take the same value from positive to ground. But it felt more like a residual voltage. I will have my daugther start the car for me today and I will monitor the test pulse voltage. Or I'll just attach a test lamp to it.
I'm on the same page as you on the motor being 12vdc. But for some unknown irrational reason, I'm a bit relunctant on applying 12 v. to the motor.
With direct 12v, the butterfly should close. How fast? Depends on the internal gear ratio. I will start by just flashing 12v to it. See what it does. If there is no internal sw in the actuator, constant 12 v will just snap the cable at the end of the race. If there are no internal sw. then the sensor probably controls the voltage being applied, or the amount/lenght of the 12v pulse. Putting 12v to the actuator will by-pass the sensor, therefore, maybe, leaving no protection to the actuator.

 

[Sportedge]

Wow, this is interessing...
Today is a national hollyday for us, so all the stores are closed.I started by hooking my working test light to the actuator plug. Turned the key to run and nothing. The test light does not lit. But, the ASC light in the dash came off after the self test. I know for a fact that when you turn the key to run and the plug of the actuator is not connected, both the ASC and the ABS light remain on after the self test. Funny. Did I tricked the computer with the test light? I took the reading of the setup I did for my test lamp, and it was 9.1 ohms!!! So the computer thought everything was fine!!!
After that, I hooked up my digital tester. Could not get any reading as it was continously searching for the right scale. So I installed my analog tester instead. Nothing. Since I could not go to the store to buy a resistor, I installed a small 8 ohms speaker to the plug. Turned the key to run again, self test proceded, then all lights went off like it should, ASC light was off (the computer was being tricked by the 8 ohms speaker), but right after the self test ended, the speaker started popping at a regular pace. That was the 2.something volts that I picked up yesterday.
The only test left is to disconnect at the ASC module and check the wires for good conductivity. Voltage may be present, but if the wire is damaged and there is only a few braid left on that wire, it wont be able to carry enough amps to perform any kind of work.
Obviously, I do not know how this system works. Why was'nt the speaker popping while the self test was being on? There is no voltage present at the actuator on the self test, but the computer still sense it's connected. And why is there always 2 volts at the actuator after that? And what makes the ASC light turn on randomly like it has been, except for a faulty wire? Code 102 said that the actuator had a faulty mechanism...
Any other ideas?

 

[NZ00Z3]

Hi

Since the ABS/ASC is a safety system, it looks like BMW have set it up as a fail safe system e.g. it has a monitoring system on the actuator. The 2 V when the car is running is a test voltage just like your multi meter and the module is looking for around 250 mA current draw (2 V/8 ohms). If the current draw is out of spec, it trips the light.

Time to do your resistance test at the ABS/ASC module.

The actuator has both sides of the motor feed from the module. I suspect that this is to allow the polarity of the supply to be changed e.g. to use the actuator to drive close the butterfly and to drive it open to. The speed of operation will be quick as the butterfly has to go from full open to nearly closed and back again in a short enough time to provide a safety function.

Hope this helps.

 

[Sportedge]

Thank you for hanging on. I doubt that the ASC module drives the actuator directly. I'm pretty sure it's going through a relay somewhere, which will give me an open circuit if the relay is not activated or by-passed...
But then again, the code said it was mechanical, as if it felt more pulling resitance, or a jerking motion or lag. There must be hundreds of wires running back there and everything works well. Why would 1 or 2 wires be damaged? Yeah, I know, I need facts...
I'm looking foward removing the glove box and it's surrending as much as I would like a thoot pulled! That section of the car was tore and destroyed by the PO. I had to re-do everything and now that it looks perfect and does'nt rattle or squeal, I really dont feel like doing this, so much that I may cut the inside of the glove box to access the modules, and repair with a thin rubber mat...

 

[NZ00Z3]

Check out the below link for the electrical drawings. There is no relay between the actuator and the module
http://www.wedophones.com/Manuals/BMW/1998 BMW Z3 - M Roadster Electrical Troubleshooting Manual.pdf

Dropping the glove box and kick panel is fairly easy. Easier than cutting holes in the glove box and trying to work through it.

 

[Sportedge]

Yes, I know, but my glove box is partially glued and held in place by a few concealed screws. Thanks for the drawing. I'll take a look at it tomorrow. Time for bed now.

 

[Sportedge]

Hi, I tested my circuit. First started by checking the resistance, once more, of the actuator. This morning, it was at 2.5 ohms!!! How is this possible???
Anyway, I unplugged the connector at the module, plugged the actuator back and took my reading: 2.7 ohms
So the wires are good. While I was there, I did 1 wire at a time, and both gave me .2 or .3 ohms. I hooked everything back up and started the engine right away, expecting to see the ASC light on, but it wasn't. Took her for a spin, and there it was again. So I thought: that's it. I installed a 8.5 ohms 1w resistor that I bought earlier this morning. Installed the resistor instead of the actuator, went for a drive and the light came back again. Back in the driveway, I installed a 1,5 ohms resistor instead. Same result. I installed the two resistors together for a 9.7 ohms (10.4 mesured) and went again for another drive. Light on again. I stopped by the side of the road and disconnected the ASC sensor at the auxiliary TB. Now, both ABS and ASC light were on. Plugged the sensor back and went home.
Any other ideas are welcome. I'm not a quitter. I never quit. But I guess that for this time, I think I'm done, being out of ideas. And I have been at it way before this post. Can't waste any more time trying to fix something while the weather is perfect and the car is fully functionnal, rergardless of that stupid light.