90' 735i TRANS PROGRAM issue

[OneWire]

I could use some help. I own a 1990 735i BMW which was running fine since
I bought it 7 months ago. I was driving along at about 60 MPH and had
noticed my "E" / "M" light out on the dash; so I put the car in neutral
and then back into gear to see if it was just a contact issue. When I put
the car back in gear, it reved up as if I wasn't applying enough gas for
the current speed. My dash indicators now appeared.

I drove on another 30+ miles to work with no problems; then drove back
home (40 miles) without and problems either. The next day on my way home I
accelerated from a stop light and realized that the car was reving higher
than normal (it should have shifted at about 1500 but didn't). The RPM's
rose to about 2400 and then "TRANS PROGRAM" and "Clunk". I was in what I
no know to be called limp mode.

I try to do all my own electrical work after serving in the US Navy as an ectronics technician for over 10 years. I have been trying to figure this out but nothing conclusive yet. Here is what I have gone through:

1. Pulling over and turning the car off then right back on often makes the
problem go away ; smooth shifting and no Trans program light.

2. My alternator is putting out 13.20 - 13.77v (I thought that this was
erratic and low so I replaced the voltage regulator) Voltage regulator now
put out 13.85 13.95v - (it's the lower voltage when reving the engine ??)
I checked the voltage output with the battery disconnected and it made no
difference. *From what I have read, 13.8 - 14.2 is the ideal range.
**I had the battery load tested today and it checked good along with the charging rate.

3. Before the car revs up to 2400 RPM in 1st gear, if I switch to "M" mode
I can prevent the car from jumping into TRAN PROGRAM mode.

*I have don electrical troubleshooting on the MAF and Throttle
position I cleaned the MAF and now both of these electrical outputs cheked good. In fact, the car even runs smoother now (well, if I make it beyond the TRANS PROG issues)

- I have not experienced any reverse problems.


Any advice is appreciated in advance.


Thanks,

Theó

[OneWire]

under the hood.

My next step before monday when Theo meets the stealer Part I begins, I plan to test the voltage coming from the transmission speed sensor to the transmission control unit.

...

[shogun]

clean the switch first
http://www.nmia.com/~dgnrg/page_13.htm

Also have a look at my website below, wiring diagrams are online.

[Bill R.]

unit and open it up, you'll see a relay in the middle of the circuit board, odds are good that the solder joints for that relay are cracked, check and resolder any questionable joints you find on the board, I touched up a number of them on mine, end of transprogram problem for my car.http://www.bimmernut.com/%7Ebillr/images/transcomp%20copy.jpg

http://www.bimmernut.com/%7Ebillr/images/transcomp1%20copy.jpg




I could use some help. I own a 1990 735i BMW which was running fine since
I bought it 7 months ago. I was driving along at about 60 MPH and had
noticed my "E" / "M" light out on the dash; so I put the car in neutral
and then back into gear to see if it was just a contact issue. When I put
the car back in gear, it reved up as if I wasn't applying enough gas for
the current speed. My dash indicators now appeared.

I drove on another 30+ miles to work with no problems; then drove back
home (40 miles) without and problems either. The next day on my way home I
accelerated from a stop light and realized that the car was reving higher
than normal (it should have shifted at about 1500 but didn't). The RPM's
rose to about 2400 and then "TRANS PROGRAM" and "Clunk". I was in what I
no know to be called limp mode.

I try to do all my own electrical work after serving in the US Navy as an ectronics technician for over 10 years. I have been trying to figure this out but nothing conclusive yet. Here is what I have gone through:

1. Pulling over and turning the car off then right back on often makes the
problem go away ; smooth shifting and no Trans program light.

2. My alternator is putting out 13.20 - 13.77v (I thought that this was
erratic and low so I replaced the voltage regulator) Voltage regulator now
put out 13.85 13.95v - (it's the lower voltage when reving the engine ??)
I checked the voltage output with the battery disconnected and it made no
difference. *From what I have read, 13.8 - 14.2 is the ideal range.
**I had the battery load tested today and it checked good along with the charging rate.

3. Before the car revs up to 2400 RPM in 1st gear, if I switch to "M" mode
I can prevent the car from jumping into TRAN PROGRAM mode.

*I have don electrical troubleshooting on the MAF and Throttle
position I cleaned the MAF and now both of these electrical outputs cheked good. In fact, the car even runs smoother now (well, if I make it beyond the TRANS PROG issues)

- I have not experienced any reverse problems.


Any advice is appreciated in advance.


Thanks,

Theó

[OneWire]

Thanks Bill..

My cleaning had no effect on the problem and today, my luck ran out on simply shutting off the engine and restarting.

I'll try that immediately.

[OneWire]

I have cleaned both the A/M program switch and the range switch.

Range switch - was very dirty, but now is very clean!
Program switch - sealed and not dirty at all, but I still opened it up and gave it a blow out with some compressed air.


Thanks Shogun, it's a pleasure to hear from you.

[OneWire]

I re-flowed the solder joints which you indicated as well as re-flowwing any other cold solder joints found in either the electronic transmission conrtol unit or the motronic unit.

- unfortunately there was no improvement in transmission behaivior.

[OneWire]

**The notorious transmission SPEED SENSOR

(details) - I decided that I needed to do some hands-on electrical troubleshooting, starting with the wiring to and from the transmission control unit. After performing resistance tests of all the connector pins referenced on the wiring diagram, I discovered that speed sensor coil was reading 3.5 Mega-ohms as opposed to 800-1.6 k ohms.

I raised the car, and did a continuity test between the following pins:

TCU connector pin #27 ------> Transmission conector cable Pin #3
TCU connector pin # 8 ------> Transmission connector cable Pin #4

*I only did this in hopes of discovering a broken wire... instead of the appearent failed part.

Next I checked the resistance at the actual pins on the connector which tie directly to the speed sensor: (pin #3 & pin #4). I got the same bad reading 3.5M ohms.


So, now I have two questions which require some transmission experience:

1. Is there a remote chance that the speed sensor wiring within the transmission is simply broken?

2. Should I be able to just drop the transmission oil pan, see the speed sensor and remove and replace it with minimal effort?

My transmission is a 4-HP-22 .

***I have seen some exploded view illustrations of the tranny.
ASSUMPTION: It looks like the speed sensor and the solenoid valves are accessable once the pan has been removed.

All advice is welcome :)

[OneWire]

I located the part which I need:

Item #04 PULSE GENERATOR 1 24341218551 $26.74
reference link: http://www.realoem.com/bmw/showparts.do?model=GB43&mospid=47359&btnr=24_0751&hg=24&fg=15

I bought it from my local Bellevue, Washington $tealer for $34.49 + tax.

[OneWire]

Fingers crossed....;)

[OneWire]

The test drive was sweet! I had immediate gratification after turning the corner on my block and noticing only by the tachometer that I had smoothly transitioned from 1st to 2nd gear.

All gears transitioned smoothly under both slow and agressive driving. To add frosting to my cake, the adjustments to my valves and Air Flow Meter have resulted in improved performance as well. (sound and speed)

**I used Pensoil Dextron III ATF to replace the 4 quarts of oil which I let off during the speed sensor replacement process. I looked up the oil spec. for my ZF 4-HP-22 on ZF transmission on the ZF website. They called out for simply Dextron III. I called them to verify and they confirmed that any Dextron III would do the trick :)

Photos:

1. the bad speed sensor (http://www.tmrus.com/bmw/images/spd_sensor_bad_dmm.gif)
2. the good speed sensor (800 ohms - 1.6k ohms) (http://www.tmrus.com/bmw/images/spd_sensor_good_dmm.gif)
3. the transmission under belly (http://www.tmrus.com/bmw/images/trans_wo_cover.gif)
4. the speed sensor's home (http://www.tmrus.com/bmw/images/spd_sensor_hole.gif)
5. the speed sensor connector (http://www.tmrus.com/bmw/images/spd_sensor_conn.gif)
6. the speed sensor installed (http://www.tmrus.com/bmw/images/spd_sensor_installed.gif)

Special thanks to Bill R. and Shogun.



Theo
"Fear None,
Respect All"

[shogun]

Hi Theo,

congrats that it runs again. And also a special thanks about the reporting of the repair stages in detail.
Helps us all for the next problem case.
And for Atsugi (your email), I have been there last weekend.
Hope you enjoyed the time in Japan.

[Bill R.]

easy fix.. Will have to file this away for future referance.



ee
The test drive was sweet! I had immediate gratification after turning the corner on my block and noticing only by the tachometer that I had smoothly transitioned from 1st to 2nd gear.

All gears transitioned smoothly under both slow and agressive driving. To add frosting to my cake, the adjustments to my valves and Air Flow Meter have resulted in improved performance as well. (sound and speed)

**I used Pensoil Dextron III ATF to replace the 4 quarts of oil which I let off during the speed sensor replacement process. I looked up the oil spec. for my ZF 4-HP-22 on ZF transmission on the ZF website. They called out for simply Dextron III. I called them to verify and they confirmed that any Dextron III would do the trick :)

Photos:

1. the bad speed sensor (http://www.tmrus.com/bmw/images/spd_sensor_bad_dmm.gif)
2. the good speed sensor (800 ohms - 1.6k ohms) (http://www.tmrus.com/bmw/images/spd_sensor_good_dmm.gif)
3. the transmission under belly (http://www.tmrus.com/bmw/images/trans_wo_cover.gif)
4. the speed sensor's home (http://www.tmrus.com/bmw/images/spd_sensor_hole.gif)
5. the speed sensor connector (http://www.tmrus.com/bmw/images/spd_sensor_conn.gif)
6. the speed sensor installed (http://www.tmrus.com/bmw/images/spd_sensor_installed.gif)

Special thanks to Bill R. and Shogun.



Theo
"Fear None,
Respect All"