Throttle position switch dis-assembly? Testing, technical data

[Dash01]

TPS for automatic transmission version of M30 engine is not giving correct electrical signals at idle and WOT positions. This is the type with 6 pins and a circular plug and over-center swivel clip.

How best to dis-assemble and inspect/repair?

The housing is very well glued together, and the plastic after 24 years is surely brittle. I have used an Xacto knife to cut into the glue line at the joint between upper and lower halves of the housing, but am hesitant to try and pry it apart as it may break.

Ideas? Solvent in the glue line to soften the glue?


(New replacement is not cheap.)

[shogun]

there is something from page 103 of 228 here how to measure, not sure if that helps, pretty old https://web.archive.org/web/20120404...escomplete.pdf big file, 7 MB!!
that covers the M30 engine in a 535 E34

[Dash01]

Well, I checked for continuity per the instructions I found for this 6 pin type of TPS, and the idle position is OK--gets continuity between pins 4 and 6. The WOT check failed between pins 5 and 6, so the part is faulty.

One source online says this part has both switch and potentiometer.

However, pictures of an opened part as linked by one of Shogun's posts from some months ago, show 2 or 3 switches.

I will use a razor saw and try and open this part and see what is inside, then fix it.

[shogun]

found more:
Throttle potentiometer sensor (TPS)
A TPS is provided to inform the ECM of idle position, deceleration, rate of acceleration and full-load (WOT) conditions. The TPS is a potentiometer with three wires. A5-volt reference voltage is supplied to a resistance track, with the other end connected to earth. The third wire is connected to an arm which wipes along the resistance track, and so varies the resistance and voltage of the signal returned to the ECM. From the voltage returned, the ECM is able to calculate idle position (approximately 0.6 volts), full-load (approximately 4.5 volts) and also how quickly the throttle is opened. During full-load operation, the ECM provides additional enrichment. During closed throttle operation above a certain rpm (deceleration), the ECM will cut off fuel injection. Injection will be reintroduced once the rpm returns to idle or the throttle is opened.

Throttle switch (alternative to TPS)
A throttle switch; with dual contacts is provided to inform the ECM of idle position, deceleration, cruising and full-load (WOT) conditions. When the engine is at idle, the idle contact is closed and the full-load contact is open. As the throttle is moved to the fully open position, the full-loadcontact closes and the idle contact becomes open. Under cruising conditions with a part-open throttle, both contacts are' open. During full-load operation, the ECM provides additional enrichment. During closed throttle operation
above a certain rpm (deceleration), the ECM will cut off fuel injection. Injection will be reintroduced once the rpm returns to idle or the throttle is opened.

Idle speed control
Motronic uses various methods to control the idle speed during engine start-up, the warm-up period and normal hot idle. When an electrical load, such as headlights or heater fan etc are switched on, the idle speed would tend to drop. The ECM will sense the load and actuate the ISCV to increase the airflow through the valve and thus increase the idle speed. When the load is removed, the ECM will pulse the valve so that the airflow is reduced. Normal idle speed should be maintained under all cold and hot operating conditions. If the ISCV fails, it will fail-safe,with the aperture almost closed. This will provide a basic idle speed.

ISCV (2-wire solenoid valve type)
The ISCV is a solenoid-controlled actuator that the ECM uses to automatically control idle speed during normal idle and during 'engine warm-up (see illustration 6.8). The ISCV is located in a hose that connects the inlet manifold to the air filter side of the throttle plate. A voltage supply is applied to the ISCV from the battery, and the earth for the motor is made through a connection to the ECM. A duty cycle can be measured on the earth circuit to determine the opening or closing time period as a percentage of the total time -available.

ISCV(3-wire rotary type)
The ISCV is a rotary actuator that the Motronic ECM uses to automatically control idle speed during normal idle and during engine warm-up. The ISCV is located in a hose that connects the inlet manifold to the air filter inside of the throttle plate. The rotary ISCV.is a DC motor that the ECM can rotate either clockwise or anti-clockwise. Rotating in one direction will open the valve; rotating in the opposite direction will cause it to close. A voltage supply is applied to the ISGV from the battery, and the earth for the motor is made through two connections to the ECM (see illustration 6.9). Rotation of the motor in the appropriate direction is accomplished by actuating the motor through one or the other of the earth circuits. In reality, the two circuits are opposed. This prevents the valve from being fully opened of closed in one particular direction. The valve will thus take up an average position that reflects circuit bias to be open or closed. Normally, this bias would be towards the open position. A duty cycle can be measured on each earth circuit to determine the opening or closing time period as a percentage of the total time available.

[Dash01]

I took the lid off my 6 pin, round plug TPS part number 0 280 120 406.

Lid was glued on pretty well, removed by use of razor saw along the glue line and careful not to cut deeper than 1/16"..

Inside is a microswitch for idle position, plus two-track rheostat swept by two brass contacts on an armature rotated by the throttle rod, plus another cam driven pair of points.

Testing shows the idle switch works with continuity between pins 4 and 6 when the armature comes off idle position, per Bentley. But at WOT position the rotating center cam activates nothing as there is noting to activate, so multimeter gets no result at WOT despite what Bentley says. In other words, there is nothing about the design of this device which would change any signal at WOT: When rotated away from idle position, a microswitch button activates, making continuity. Rheostat sweeper contacts are always engaged, and the cam driven contacts connect at about 60 degrees of rotation. This makes me suspect Bentley is wrong about WOT continuity.

I have the exact same TPS on my other 535i, and tested it still on the car with a multimeter. Same result: Continuity between pins 4 and 6 as soon as it rotates off idle, no change between pins 5 and 6 at WOT.

I messed around checking continuity between various pins, rotating the armature back and forth, to see what the rheostat output is. No reaction anywhere but between pins 4 and 6 coming off idle.

Anybody know what the rheostat does, or what it's output should be? I've read this may be related to automatic transmission shifting, but so far have found no information on this.

[E32FAN]

I found that you cannot test the rheostat with an ohmmeter.

You need to feed it with 12V and then measure the wiper output voltage. You will see that the output voltage changes very nicely as the throttle plate rotates.

[Dash01]

I found that you cannot test the rheostat with an ohmmeter.

You need to feed it with 12V and then measure the wiper output voltage. You will see that the output voltage changes very nicely as the throttle plate rotates.

Good input, and thanks!

By feeding 12V, do you mean install TPS in car, turn on key, and measure voltage at the pins, at the ECU multipin plug, both, or what?

[E32FAN]

Sorry, I was thinking of the Air Flow Meter!

The S200 Throttle Switch is shown on pg 1360-07 at http://www.e38.org/e32/e32_92_etm.pdf

Its connector X6251. Pin 4 connects to pin 6 at idle, and 4 to 5 at Full Load (WOT). You don't need to worry about WOT unless you are on a drag strip. (That's no place for a 20 year old car.)

Pg 8500-17 has a diagram of X6251. This is a view of the connector to the cable harness, not the connector on the switch.

So is there a rheostat in your TPS? What is your VIN?

[Dash01]

My 6 pin, round plug TPS is Bosch part number 0 280 120 406, came on M30 engines of E32 and E34 variety. I've read also E24, E28, and E30, but don't know for sure.

Has microswitch activated coming off idle position.

Has sweeper double track rheostat.

Has cam-operated points that break contact when the center shaft/cam rotates to about 60 degrees.

Does not appear to have WOT switch.

[E32FAN]

OK, does the Microswitch connect pins 4 and 6 together at the idle position?

And are pins 4 and 6 open-circuited at off-idle?

If so, then the only issue would be pin 5. According to the diagram, if pin 5 never connected to anything that would be fine. If it does connect to another pin sometimes, then cut the wire to pin 5 so it does not.

This would turn the TPS into an Idle Position Switch. So it only tells the DME that we are leaving idle and we need some revs.

[Dash01]

OK, does the Microswitch connect pins 4 and 6 together at the idle position?

And are pins 4 and 6 open-circuited at off-idle?

If so, then the only issue would be pin 5. According to the diagram, if pin 5 never connected to anything that would be fine. If it does connect to another pin sometimes, then cut the wire to pin 5 so it does not.

This would turn the TPS into an Idle Position Switch. So it only tells the DME that we are leaving idle and we need some revs.

4 to 6 pin thing works as advertised, but 5 to 6 does not get continuity with shaft in in any position. Opening the unit, I don't see how it could get continuity, since there's no contact point at the WOT end of rotation.

That leaves the rheostat twin tracks and pins 1, 2, and 3 to account for. Attaching alligator clips on my multimeter to those and with both volt meter and beeper settings, no response whatever in any combination of pins.

So, I'm doing something wrong with my test procedure or the unit is faulty.

Ideas?

Anybody with experience in this particular TPS please chime in.

[EEDegreeToDrive]

4 to 6 pin thing works as advertised, but 5 to 6 does not get continuity with shaft in in any position. Opening the unit, I don't see how it could get continuity, since there's no contact point at the WOT end of rotation.

That leaves the rheostat twin tracks and pins 1, 2, and 3 to account for. Attaching alligator clips on my multimeter to those and with both volt meter and beeper settings, no response whatever in any combination of pins.

So, I'm doing something wrong with my test procedure or the unit is faulty.

Ideas?

Anybody with experience in this particular TPS please chime in.

I recall the same on my '89 735i, tested at the connector
Microswitch for IDLE and 3 pin potentiometer, I had nothing that "closed/opened" at WOT. No Micro for WOT' despite the ETM says so. I thought my TPS/switch was bad too, until reading this thread. I haven't disassembled mine, and don't intend to.

I still have an issue coming off IDLE, though. My car stumbles just off idle. (i.e. if I modulate my foot from IDLE to ~5% repeatedly I can almost get the car to stall.) I suspect my TPS needs a cleaning or my IDLE micro/potentiometer is off by a few degrees (if that is even possible)

Besides, that's what the kick-down switch is for! I call it the "I'm serious button"

[E32FAN]

TPS for automatic transmission version of M30 engine is not giving correct electrical signals at idle and WOT positions.

Sorry, but can you rewind and share with us what the problem is with your engine? Does it stumble on acceleration, etc.?

AFAIK, if 4-6 is shorted at idle and not shorted with the pedal depressed, then you should be good to go.

What symptoms led you to suspect the TPS?

Just trying to help.

[Fast 7]

does anyone know what size pin tool to use to remove the pins from the tps plug for the tps sensor? i have tried eveyone that snapon makes and they are all too big for the round pins. I dont want to cut the wires to move the pins for my megasquirt setup but i will if i can't get the pins out to move them.

[Dash01]

I recall the same on my '89 735i, tested at the connector
Microswitch for IDLE and 3 pin potentiometer, I had nothing that "closed/opened" at WOT. No Micro for WOT' despite the ETM says so. I thought my TPS/switch was bad too, until reading this thread. I haven't disassembled mine, and don't intend to.

I still have an issue coming off IDLE, though. My car stumbles just off idle. (i.e. if I modulate my foot from IDLE to ~5% repeatedly I can almost get the car to stall.) I suspect my TPS needs a cleaning or my IDLE micro/potentiometer is off by a few degrees (if that is even possible)

Besides, that's what the kick-down switch is for! I call it the "I'm serious button"

The body of the TPS is adjustable as it mounts to the throttle body on M30 engines. Just slacken one or both phillips screws that mount it, and rotate slightly as the mount holes are slotted for this purpose. Get a multimeter and set it to beep when it gets continuity, and attach alligator clips to pins 4 and 6, which are cast into the plug beside the pins. You may need reading glasses and good light to read the tiny numbers. Anyhow, with the throttle cables properly adjusted for idle and the butterfly gap properly set to ~0.020" or so, simply rotate the TPS a bit in its slotted holes to where the multimeter will beep just as the butterfly valve comes off idle. Tighten the screws. Now, it triggers just as you activate the pedal/cables/butterfly.

I was messing with my TPS as the engine runs like crap even after new Mustang 3 injectors, so am going through the various sensors, potential vacuum leaks, etc. one by one. Bentley says TPS should get continuity (short circuit) between pins 4 and 6 coming off full idle, and again at WOT. However, Bentley is surely wrong about this particular TPS for automatic transmissions, as its internal circuitry simply has no microswitch or contact point existing to do WOT. It ain't there. Does have twin arcs for sweeper rheostat, microswitch at idle position, and cam-driven contact points at ~60 degrees of rotation, but nothing to make any change at full WOT. That's why I'm pestering you guys, to find out how this sucker is supposed to work.

Anyhow, thanks to all for input and for further insights.

[Mordan]

Hello,

I also have this kind of TPS with 6 pin connector.

I'm suspecting it because my auto tranny shifts gears at 5500 RPM at WOT.

I'm disappointed to learn there is not WOT switch. At least it is easy to test. Is there any means of testing the potentiometer?

From my understanding, these 3 pins go to the tranny ECU and then the tranny ECU sends the WOT signal to the Motronic ECU. That would explain why there is not WOT switch.

You still need a way to test the potentiometer.

Pin 1-black wire-5volt in
Pin 2-shielded wire-ground
Pin 3-yellow wire-signal out

Here is how they say how to test it.



How do you do that with just a basic multimeter without cutting the wires?

[bonfirebarry]

this is a rookie question but i cant seem to find where the sensor is physically located on my 91' 735i if someone could provide a picture or diagram i would be grateful

[shogun]

http://www.bimmerboard.com/members/s...view_735_1.jpg
http://www.bimmerboard.com/members/s...view_735_2.jpg

[G46]

thank god i found this thread, reviving it somehow

my car wasnt revving past 2k rpm. i noticed the tps was giving bad output due to, when idling, its low as 500+/- then i tap the tps, it raises the idle to 750+/- i took it for a ride, it will rev past 2k, but after removing feet from the throttle pedal (braking) and continue to rev, it will not go past 2k,

found this thread and measured 4 & 6, no continuity, tapped the tps, bamm got continuity, move throttle plate off idle, remain in continuity, (ecu senses still idling) thats why it wont rev past 2k. not enough fuelling i guess
then regulate as throttle plate open and closing few times, 4 & 6 remain in contact tapping the tps causes on and off continuity also between this 2,

at WOT, 5 & 6 got continuity, which is normal.

TPS.jpg

decided to hack open the tps, found out the plunger for tps did not even return (spring return)

desoldered the pin for microswitch. hack open the microswitch, found the spring is in no tension or whatsoever, the spring snapped of from one side of spring holder (28 years old car with heat changes inside the engine bay)

DIY the spring holder with a stainless steel pin, heat it till glowing red and plant it to the microswitch body.


then the spring is held on one side, the other side of the spring is held on to moving contact. the plunger then makes the contact on idle, when the throttle plate move, it returns by spring action, breaking the contact.

microswitch.jpg
the red dot marked red with a red arrow will be brittle over time. and the tension of the spring would break that stuff easily.


TPS 0 280 120 406


the red dot marked red with a red arrow will be brittle over time. and the tension of the spring would break that stuff easily.

i heat a stainless steel pin which fit enough on the hook end of the spring, and plant in on the plastic. need abit of force to plant it in. and let it cool down naturally.

to install back everything in a correct order, especially the contact which the spring pulls as a tension, its PITA to put it back in. i spent 1 hour thinking of an idea how to make it work + plant the stainless steel pin, and another hour to put it all back together.

test by multimeter (ohms or beeper)

the switch is a normally open switch, where there shud no continuity between 4 & 6, and if you press the microswitch plunger, continuity should be there, or the your multimeter will beep (if you set it to beeper)

next is adjusting the tps on your car, slight movement of throttle flap (press the gas pedal or simulate using your hand on the throttle linkage, should open the circuit.

however, for cars with EML, i am not sure about this.

[G46]

sorry, on the internal microswitch diagram, the pin shoud be the other way round, lol im drawing it as best as i could, and im at the office, lol, sneaking through bimmer forum

[shogun]

this might also be of interest to you: Cleaning the Air Flow Meter (AFM) Potentiometer http://web.archive.org/web/201804302...730i/index.htm

[shogun]

I read now several threads on a German forum where a bad throttle posiition sensor caused hard and faulse shifting of the automatic transmission One even changed the trans on an E34 535, did not help, then he installed a new TPS and the transmission problems were solved.
Here are the pinouts for the M1.1 and M1.3 from E30, just to give you an idea http://www.rtsauto.com/ecu-pinout-an...cal-tests-e30/

[G46]

adding to this, the tps must be in a correct mounted, either from the left or the right side, i have issue when buying used tps, its mounted on the wrong side, causing erratic shifting, it hardly shift until 4-5k, and when i release the throttle, it downshift hard, the root cause is wrong tps, the computer sees WOT instead of idle.

[Annddrriy]

Go to machine shop the machine guy will make it for you anythink you like.

[Annddrriy]

does anyone know what size pin tool to use to remove the pins from the tps plug for the tps sensor? i have tried eveyone that snapon makes and they are all too big for the round pins. I dont want to cut the wires to move the pins for my megasquirt setup but i will if i can't get the pins out to move them.

Go to machine shop the machine guy will make it for you anythink you like. Give him dimensions.