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Topic: TPS not communicating with Allison after air throttle install (Read 647 times) previous topic - next topic

TPS not communicating with Allison after air throttle install

I just converted from the King Controls throttle to a Williams air throttle. Works great, but I cannot get the new TPS to communicate with the transmission. I'm experiencing the classic symptoms, specifically upshifts only occurring at rpm's in the 2,200-2,400 or higher range.
Other forum members who've done this conversion successfully have connected the TPS to a 3-wire harness coming from the Allison with wires numbered 135A (green), 156 (blue), and 124 (red), as seen in the first photo. I have searched all through the tangle of wires going into the King and cannot locate either those wire numbers or those colors. Instead, what I see is what is in the 2nd photo: the King connected to a 3 wire harness coming out of the "filter" with black, white and red wires. When I connect my TPS to that harness though the transmission still performs as if there is no TPS.  Has anyone who has successfully done this conversion know where I should be connecting my new TPS? Does the "filter" need to come out of this setup perhaps?

Re: TPS not communicating with Allison after air throttle install

Reply #1 –
Sorry I can't give any specific info, but the typical TPS sensor has a 5V power, ground and a signal output...knowing that, you should be able to determine what wire is what.

Re: TPS not communicating with Allison after air throttle install

Reply #2 –
Quote from: WS6_Keith –
Sorry I can't give any specific info, but the typical TPS sensor has a 5V power, ground and a signal output...knowing that, you should be able to determine what wire is what.
I'm not sure what you mean by "signal output." So, walk me through this. I clamp one lead from my multimeter to a known chassis ground. With the ignition on, test each of the three wires coming from the filter. Find the wire with 5v. Test the other wires for... what?

Re: TPS not communicating with Allison after air throttle install

Reply #3 –
Quote from: Dan & Annie –
I'm not sure what you mean by "signal output." So, walk me through this. I clamp one lead from my multimeter to a known chassis ground. With the ignition on, test each of the three wires coming from the filter. Find the wire with 5v. Test the other wires for... what?

When you find the five volts the other 2 are ground and signal, finding the ground leaves you with the third wire being the signal.

Re: TPS not communicating with Allison after air throttle install

Reply #4 –
Quote from: craneman –
When you find the five volts the other 2 are ground and signal, finding the ground leaves you with the third wire being the signal.
What does that mean, the "signal"? Is that what would be being returned to the ECU as the value of the TPS?

Re: TPS not communicating with Allison after air throttle install

Reply #5 –
yes but which wire it connects to match up with the Allison I can't help with.

Re: TPS not communicating with Allison after air throttle install

Reply #6 –
You have it correct Dan.  One will likely read 5V when metered between the wire and ground.  If you have a continuity setting on your meter (with the beep), finding the ground would be easy too.  The output of the signal wire is generally in the 0.5-4.5 range, but they vary as to actual 0% and 100% voltages. 

Re: TPS not communicating with Allison after air throttle install

Reply #7 –
Based on the KC2600 diagram other white wires are ground, so black is power and the other is signal.

Remove filter.

Re: TPS not communicating with Allison after air throttle install

Reply #8 –
I have identified which wires are which - Green A=ground, Blue B=signal, Red C=power. This I got from reviewing Allison schematics. When I put the multimeter on though, none of those wires downstream from the filter show any voltage, nor do any appear to be ground.
I'd like to try to find the far end of these wires, where they terminate in the ECU. Does anybody know where the ECU is in this '98 U295?

Re: TPS not communicating with Allison after air throttle install

Reply #9 –
If the filter is stopping any information/voltage from going to the trans, then it sounds like you may have found your issue.  Look at the post above yours...Barry & Cindy said to remove the filter as well.

Every Cummins I've ever worked on has the ECM mounted on the right side of the engine (looking at it from it's front where the crank pulley is, so from the rear in our coaches), almost to the back of the engine block below the cylinder head level.

Re: TPS not communicating with Allison after air throttle install

Reply #10 –
Isnt the signal going to the transmission control module located near the shift pad?  Always assumed that but could be mistaken.

Re: TPS not communicating with Allison after air throttle install

Reply #11 –
Found it!
Cut off the filter, stripped the wires and there it is, Red = Power 5.3V, Black = ground, White = signal.
It appears the filter was blocking any signal from the transmission to the King (power and ground) and allowing only throttle position data back the other way from King to Allison.
Also interesting to note is the ground is only ground when the ignition is OFF. Turn the key on and it stops being ground.
I'll finish hooking it up and test drive tomorrow.

Re: TPS not communicating with Allison after air throttle install

Reply #12 –
Took it for a 15 mile test ride this morning. All is well. Drove beautifully.
This was a project I did not want to undertake 6 weeks ago. Kind-of felt it was beyond my ability, but I had no choice. As of today I think I can say it is done, and it was successful. We'll do additional test rides around home before we trust it to a cross-country jaunt in September, but I'm pretty happy about things at the moment. Thank all of you who've offered your help and support!
 

Re: TPS not communicating with Allison after air throttle install

Reply #13 –
Congratulations. I hope my King control keeps working but you have added some important info for the rest of us that may prove to be a life saver. Would love to see your part list and photos of brackets.