Torque Converter Lock / Unlock Issues

[balsip]

Yeah but if the alternator is the source of the ripple and now feeding it to all systems (ECM, PCM, ABS, airBag, Etc.) So filtering the PCM cures the TQ lockup issues but how about VP4 failures, ECM failin, etc... I'm figuring that some of these failures are from the AC from a shorted diode. Why is it that the rest of the problem disappear when the alternator fuse is removed? This why I'm still highly against the idea of using filters, extra grounds, etc... Because all you do is band-aid the problem but the alternator is still beating up every other electronic device on the truck. Why not fix the source of the AC noise? Because if the diode failure happens on the negative side then AC pours through the grounds... If it happens on the positive side then some filtering might occur but still most DC electronics are not designed for AC noise. Here is a basic alternator circuit... Take notice there is 6 diodes (3 positive and 3 negative) if I should short out in either side that will be the side the AC waveform leak out on... More diodes fail the worse the problem gets. But in the DC life the gauge will continue to read 14 Volts even though the diodes are bleeding AC wave form. [ATTACH=CONFIG]4153[/ATTACH]

Man you are quick and accurate! I am now thinking back to an ATS fix that involved altering the ground instead. http://www.atsdiesel.com/additionalinfo/3092218/4th%20Gear%20Hunt%20Fix%20(1998-2002)%20v1.0.pdf I would think a shorted diode would be so overpowered by the batteries that it would blow the fusible link rather than the electronics. The VP44 electronics is a heat problem that has supposedly been improved. The ECM is also a heat problem that will never be fixed but more rare. The other microprocessor failures are quite rare as far as I know? See what you think. I believe the other processor circuits are not affected because it is only the APPS input grounding that has the noise voltage drop. I am not sure of the mechanism but the most usual reason is because the ground is shared by another high current circuit that causes the noise to show. I agree filters are the dirty way and electolytics may not like my cold climate in the winter but when I get onto it I have a hard time giving up on a problem so I start trying anything that shows promise. If I had an ocilloscope I could look at the noise real time at the PCM connector by back probing, then keep the ground at the PCM and probe at the APPS to see the difference. I may just try that ATS fix if anyone has tried it with success.

[hex0rz]

Mike, are you going to make this a techie, or is it already?

[Mopar1973Man]

Man you are quick and accurate! I am now thinking back to an ATS fix that involved altering the ground instead. http://www.atsdiesel.com/additionalinfo/3092218/4th%20Gear%20Hunt%20Fix%20(1998-2002)%20v1.0.pdf I would think a shorted diode would be so overpowered by the batteries that it would blow the fusible link rather than the electronics. The VP44 electronics is a heat problem that has supposedly been improved. The ECM is also a heat problem that will never be fixed but more rare. The other microprocessor failures are quite rare as far as I know? See what you think. I believe the other processor circuits are not affected because it is only the APPS input grounding that has the noise voltage drop. I am not sure of the mechanism but the most usual reason is because the ground is shared by another high current circuit that causes the noise to show. I agree filters are the dirty way and electolytics may not like my cold climate in the winter but when I get onto it I have a hard time giving up on a problem so I start trying anything that shows promise. If I had an ocilloscope I could look at the noise real time at the PCM connector by back probing, then keep the ground at the PCM and probe at the APPS to see the difference. I may just try that ATS fix if anyone has tried it with success.

Actually a shorted diode is typically what causes the TQ Conv. lock/unlock issues. Actually so far the few that I've found do not over power the fuse and blown but continue pumping roughly 14-28 VAC into the circuit but on the VDC scale its still 13.5 to 14.5 VDC. The ATS fix basically takes a floating ground created by the ECM and turns into a true ground. So now if the alternator has a shorted diode on the negative side the AC wave has a perfect path to the PCM now that grounded the APPS lead. Then the ECM no longer provides the signal to the PCM but now the APPS is doing directly. There was a reason for the ECM and PCM when not wired this way in the firs place. What I look at is the fact these truck cover 9-11 years of time then now you got to consider chopping up the wiring for this little problem? (ATS wire mod, BD filter, etc.) Ok?! Then why don't why don't we see this problem over on gasoline vehicles why don't they have to chop up wiring and add filters? Why only the Cummins Automatics? PCM's are suppose to be that exact same. Let figure out the problem not band-aid the issues. As for the heat problem might be true down south. But like up here I'm still seeing temps 45-50 then might get to 60-65*F not hot buy no means. But still find ECM, VP44 failures (with > 14 PSI), ABS issues... Now I've not had a chance to apply the alternator though yet to check some of these weird failure but I will on the next one I run into. Like you see over on CF.com there is a few people that have a rash of VP44 failures with a Airdod, FASS or Raptor pumps that has good fuel pressure its entire life. This would be a good canidate to check alternator on.

[Mopar1973Man]

Mike, are you going to make this a techie, or is it already?

If you wish you can start a thread and vote for it...

[hex0rz]

Okay, I have a bit of a dilemma... maybe. I cheked my voltage on my truck with the truck running and showed 14.44V DC at both batteries. Switched to A/C voltage and it showed .16v. In your video on your DMM, it shows .016v A/C. Thats a big difference! With my truck off, I tested the A/C voltage and it was .016 or so. I DO NOT have any TC hunting problems. 'Am I looking at this wrong?

[Mopar1973Man]

Your DVM accuracy is rather low on AC it appears...

I went out and grabbed my 23 year old Fluke 75 DVM and re-tested on my Cummins...

Rest Voltage

Battery Volts AC ............. 0.001 VAC

Battery Volts DC ............. 12.62 VDC

Running Voltage

Battery Volts AC ............. 0.011 to 0.019 VAC

Battery Volts DC ............. 14.02 VDC (72*F outside temp)

0.100 Volts AC isn't a problem really... It when you see 14-28 VAC on the DVM.

[hex0rz]

Your DVM accuracy is rather low on AC it appears...

I went out and grabbed my 23 year old Fluke 75 DVM and re-tested on my Cummins...

Rest Voltage

Battery Volts AC ............. 0.001 VAC

Battery Volts DC ............. 12.62 VDC

Running Voltage

Battery Volts AC ............. 0.011 to 0.019 VAC

Battery Volts DC ............. 14.02 VDC (72*F outside temp)

0.100 Volts AC isn't a problem really... It when you see 14-28 VAC on the DVM.

So you think anything ABOVE 1 VOLT A/C is where your problem is going to arise from?

I just bought my DMM last year and its an auto ranging type..

[Rogan]

If you wish you can start a thread and vote for it...

voting closed; make it techie.

[Mopar1973Man]

So you think anything ABOVE 1 VOLT A/C is where your problem is going to arise from? I just bought my DMM last year and its an auto ranging type..

Alternator diodes. Like I just got off the phone last night with Chad (another member here) talk to him about his alternator and TQ conv and surging problem. So far what is happening is new alternator fixes the problem but in about 4-5 days the problem comes back. But now while the problem is occuring the AC voltage is jumping as high as 53 VAC but VDC is holding steady at ~14.x volts. But now take the alternator fuse out the problems are gone. So now we are trying to figure out what is causing alternator failures that are burning up the diodes. The only thing that comes to mine is the grid heater hanging up longer that it should putting alot of stress on the diodes. (Shoot from the hip and this unproven as of yet). Chad promised that as soon as he figures it out he's going to post his videos and testing results with us...

[hex0rz]

Alternator diodes. Like I just got off the phone last night with Chad (another member here) talk to him about his alternator and TQ conv and surging problem. So far what is happening is new alternator fixes the problem but in about 4-5 days the problem comes back. But now while the problem is occuring the AC voltage is jumping as high as 53 VAC but VDC is holding steady at ~14.x volts. But now take the alternator fuse out the problems are gone.

So now we are trying to figure out what is causing alternator failures that are burning up the diodes. The only thing that comes to mine is the grid heater hanging up longer that it should putting alot of stress on the diodes. (Shoot from the hip and this unproven as of yet).

Chad promised that as soon as he figures it out he's going to post his videos and testing results with us...

If a solution to the problem is found and we can find the "cause and origin", this will prove to be monumental! Think about the kind of repor this site would gain! There will be alot of people flocking and/or talking about this!

[Mopar1973Man]

This why I sunk my teeth into this one and held on for the ride. I'm tired of all the goofy and dumb ideas of chopping wiring, adding filters, etc. for a problem that should be corrected and not band-aided.So far I've mastered the VP44...So onward to the Tq Conv lock up issues!

[hex0rz]

Such a small forum, but such a large cache of wisdom.

[balsip]

Well I did a little more research and got down to looking at the actual circuits. I was quite surprised to find the APPS goes to the ECM only and not the PCM. Actually the ECM provides an equivalent analog output signal that goes to an analog input on the ECM. I bet the output is via an digital to analog converter in the ECM rather than simpler analog amplification. I also wonder whether the circuit is low enough impedance to withstand crosstalk noise from adjacent wires - most industrial computers use 4 to 20 ma current drive so they are more noise immune to crosstalk. Anyway, it is that signal that is between the ECM ("fly by wire" throttle) and the PCM (auto trans shifting software) that the noise originates. Here is a guy that put lots of research into it and seems very sharp on electrical issues even thouigh he is mechanically oriented. http://www.kentsoil.com/dodgebug1.htm Also, http://www.dieselperformance.com/index.php/product/index/185P Just remember when reading a lot of these threads that say "I wrapped a wire loom in foil and it went away, or .....". These guys usually disconnect the batteries which erases the APPS calibration and THAT can be the reason it improves and then comes back later. Mine has gotten so bad that an APPS reset only works a couple of days now. I am going to put a 330 ohm resistor in series with a 100 mfd 50V capacitor from the signal identified to signal ground to filter the noise at the PCM connectors - same as the writeup but without the series torroidal choke. The only reason for the 330 ohm resistor is to protect the ECM driver in case the capacitor ever shorts and I do not know whether that ECM is short circuit proof. I do know it is expensive to buy and get reprogrammed. 15volts / 330 ohms = < 50 mA max short circuit current. I do not know if this problem gets worse with age because of corroded ground or if the alternator diodes deteriorate. When all else fails and it is driving you to drink have a look at this thread -- it is 35 pages long! http://www.cumminsforum.com/forum/98-5-02-powertrain/168166-tc-lock-up-thread.html I will report back on how it works.

[Mopar1973Man]

http://www.kentsoil.com/dodgebug1.htm Neat article but like all the others they are working to shield a unknown noise. Why not find the source of the noise and remove it? But still the RF noise is in everything... You filtering the PCM for the TQ conv but how about everything else? (ECM, ABS, Central Timer, etc.)?

[balsip]

I really think it could be grounding of the pins 31,32 on PCM C1 as ground. When you look at the FSM the ground splice feeds a lot of other high powered circuits. Also, most analog inputs have low pass filtering in software to eliminate spikes. This would require coordination between Cummins who did the ECM and Dodge who did the PCM software. I will probably clean tighten all gounds and connect the C1 pin 31,32 direct to the battery ground. A hardware low pass filter just corrects missing low pass filtering in the PCM software. Has to be fast enough to respond to downshift within about 1/2 second so can not be too strong.

[Mopar1973Man]

Your still missing it... If the battery feed from the PDC box is live with AC waveform that means everything hook to that fuse box has AC wave form feeding it. So the alternator is creating the AC waveform and feeding that power to all these things on the PDC fuse box and more... So if you remove the fuse and the problem is gone then you kill the source of the noise. As you can see the power comes in on 48 and 50 of the ECM and 22 of C1 on the PCM. Oh the red/white going to the fuel pump relay that's the power feed to the VP44. As you can see the AC waveform from a bad alternator can be fed to every device in the truck. The other thing your missing is the fact these truck normal cover 9-11 years before this problem pops up. So what changed that now there is RF noise (AC waveform) in the electrical system that needs filtering off? There is only one device on the entire truck that creates AC waveform which is the alternator. There is the digital signal from the computers but its very small voltage scale (2.5 volts). But still I say deal with the source...

[balsip]

Mike, I totally agree with you that the problem disappears when the alternator fusible link is pulled. The theory is that it could be leaky diodes (resistance in the blocking part of the sine wave), bad diodes or even worn slip rings that arc and cause noisy charging amps. The other thing is the alternator is grounded through the mounting bolts to the engine block and they rust with age. See the attached TSB on this as Chryslers official take on this: http://dodgeram.info/tsb/1999/18-02-99.htm They say "The cause of this erratic operation has been identified as electrical noise from the Throttle Position Sensor (TPS) or Alternator." They attempted to fix it in 1999 but obviously they did not completely fix it as 1998.5 to 2005 have complaints. I really think they applied more low pass filtering in software to the APPS throttle position signal beween the PCM and ECM. The amazing thing is that they recognized the problem in 1998 and it carried on so many years and they never really updated this fix even though it was not totally fixed by this TSB - it was only improved. The 35 pages of replies in the forum link I gave above tells how many people are now seeing it as corrossion and alternator wear set in. Most people are able to get rid of it with the filter. The BD filter looks like a resistor/capacitor low pass filter. I also think the APPS signal sent from the ECM to the PCM is kind of unique because there are very few hardwired signals passed on like this. Industrial computer systems have a floating signal ground for each and every I/O while Dodge is relying on the PCM and ECM grounds being the same which is difficult in a weather prone automobile enviroment. This is the real reason we see alternator noise in other circuits yet this particular circuit is most affected by that noise. Most signals are sent via the serial link digitally(with differential driver/receivers eliminating ground differential problems between processors) but throttle position required more real time speed and was hardwired and they went cheap with a "single ended circuit" that relied on a solid common ground. I bet they send this signal digitally now that processors are so much better now. The "real fix" is to beef up the grounds and perhaps replace the alternator but a low pass filter fixes it in many cases at minimal cost and time. The BD filter is simpler than the one with a torroidal choke so probably may not work in all cases. I'll know more when I get the time to do my truck. Luckily I have a TC disable switch that prevents lockup in the city which I use when it gets real bad.

[balsip]

Just an update. I drove about a 400 km trip and that filter does seem to work well as the transmission was perfectly behaved. I must admit I loosened off three alternator mounting bolts and retightened them to improve grounding. More time will tell.

While I had the inlet air filter box off I noticed the two big ground leads molded into the passenger side battery negative post clamp. One went to the block(and eventually to alternator thru block) and the other went to the exact cable bundle on the PCM which splices to C1 term 31, 32 black/tan ground. I am convinced that a seperate welding type cable (say 4 guage with lug nut type terminations)from the negative battery post to the alternator case might also fix the problem giving a better ground reference to the alternator. An AC DVM meter would show the difference but I just did not have the time so I went with the filter. Many owners report a new alternator solves the problem but perhaps just disturbing the rust on the nuts and bolts is what really fixed the problem?

BD says the problem is RF interference but I believe it is simply the alternator 3 phase full wave rectification waveform(normal alternator signal) superimposing on the poor ground reference.

Update 25-June_2012: I hated to start a new reply so this is an add-on. Here is the BD write up.

http://www.dieselperformance.com/productManual/1300030_Apps_noise_isolator5.pdf

You can also watch their Youtube video on installing.

I had doubts about grounding it to the battery because I wanted to low pass filter exactly what the PCM sees at C1 connector but I followed their advise and grounded to the battery terminal. Saves splicing into C1 31,32 and it did work well. I have no doubt now it has improved if not solved my problem. I am not sure whether BD has the series resistor but I recommend it because electrolytic capacitors can fail shorted and destroy an unprotected processor (ECM) output (unkown whether ECM can withstand a short). I used a 100 uF 50V capacitor + 330 ohm resistor rather than the 150 uF 30 V capacitor used by BD. If my problem does come back I will ground the alternator case via welding cable directly to the battery. You can buy the components for about $10 at full retail including connectors as long as you have the wire and heat shrink tubing.

[chaney2051]

Mike,I spoke with you yesterday on the phone about this issue. I got the meter out and checked at battery DCV was 13.82 and when I switched it to ac it was showing 29.7??

[Mopar1973Man]

Mike,

I spoke with you yesterday on the phone about this issue. I got the meter out and checked at battery DCV was 13.82 and when I switched it to ac it was showing 29.7??

Failed diodes... Alternator is damaged... VAC side should show less than 0.100 volts. My two truck so typically 0.011 to 0.019 VAC...