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peterabbe

Transmission Code- Throttle Position Sensor?

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As a newbie to RVing I am slowly rehabilitating a 1993 Aerosport by HMC, 34' W/ 250 Cummins.

Transmission code on Allison MD 3060 is d-1, 2-1, 1-2. I have an appointment with Cummins dealer in three weeks, could not wait that long, called Freightliner, they had a tech on it in 30 min.

I called the Allison dealer that installed the new ECU for the trans. and they said it is not a transmission part, but an engine part, Freightliner says it's a Allison part. Help!

And is the throttle position sensor on the motor or at foot throttle?

By the way, the coach drives just fine, but has "service" illuminated on shift pad. Any help would be appreciated, thanks.

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Not fun when the tps goes out, had that happen in the early 90's. Still drove, but I had to keep moving the accelerator back and forth to keep it going.

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peterabbe,

Welcome!

You got the code correct Main Code 21, Sub Code 12 - 21 - Throttle position sensor, failed low! Use full throttle default, DNA

The sensor the ECM is looking for is a potentiometer, basically a pot. ECM not reading any voltage - so you might have an open 5 volt supply to the Pot, loose connector, broken part.

In this case, my thought is a dirty control.That pot is part of the throttle control! You might be able to reset the throttle sensor, turn key to on position and pump pedal 4-5 time from 0 -100% then back off and then start engine

NOTE: A good throttle position sensor should have resistance of:
1. 9000–15,000 Ohms across terminals A and C.
2. 500 ohms, moving to 9000–15,000 Ohms as TPS is stroked (measured across terminals A and B.

Trouble Shooting

1---If the condition persists, replace the ECU. If replacing the ECU corrects the problem, reinstall the
original (bad) ECU to confirm that the problem is in the ECU. If the original ECU now works,
inspect the ECU connectors for any corrosion or damage which may cause an intermittent
condition. If the original problem reoccurs, reinstall the replacement ECU.

2---- The only troubleshooting necessary for a PWM fault is to check for an open, short-to-ground, or
short-to-battery in the signal wire from the PWM source. An open or short-to-ground will set
Code 21 12. A short to battery will set Code 21 23.

If you have a Good Tech. this might help !

Older dumber APS designs were simple rheostats, varying 0-5V on one signal and 5-0V on the other, so the sum had to be 5V.
On the Teleflex unit:
Signal 1 should vary from 11% at Idle to 42% at WOT.
Signal 2 should vary from 22% at Idle to 84% at WOT.
You can have a knowledgeable tech probe for these values to see if the pedal assembly is currently working. A transient might be no 5V reference signal (0V or some other voltage not 5V) on one or both of the middle pins, could be a loose connector, could be a loosely made wire-pin connection on one of the signal sides, could be a loose ground, , could be a poorly made connection on its way to the ECU, etc. So fixing it might not be a matter of swapping out the pedal sensor assembly, those other types of errors should be checked first, but before that I'd recommend the above Idle-to-WOT reading checks.

Look at this link for a floor mounted unit, I think! See if you can find there catalog- It should list the parts by who's engine it is used for: Cat, Cummings and others.

http://www.cw-industrialgroup.com/Products/Electronic-Throttle-Controls.aspx

Think yours might match the WM-526 series. The key if you need a new one is the correct connector!

Hope this helps

Rich.

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As a newbie to RVing I am slowly rehabilitating a 1993 Aerosport by HMC, 34' W/ 250 Cummins.

Transmission code on Allison MD 3060 is d-1, 2-1, 1-2. I have an appointment with Cummins dealer in three weeks, could not wait that long, called Freightliner, they had a tech on it in 30 min.

I called the Allison dealer that installed the new ECU for the trans. and they said it is not a transmission part, but an engine part, Freightliner says it's a Allison part. Help!

And is the throttle position sensor on the motor or at foot throttle?

By the way, the coach drives just fine, but has "service" illuminated on shift pad. Any help would be appreciated, thanks.

Digging into the Throttle / Treadle control I did find this much information regarding the control for Cummins engine before 1994>

With a OEM part number you might find something, From the part numbers for Cummins after 1994 might work, or from the other information listed in my other post.

These parts where supplied Williams or Tectran

The difference between the 3 is the angle of the peddle - 5=28.5 Deg., 6=35Deg., and 7=45Deg.

WM351375 D n/a TREADLE-ELECT.(WM526), CUMMINS BEFORE 1994

WM351376 D n/a TREADLE-ELECT.(WM526), CUMMINS BEFORE 1994

WM351377 D n/a TREADLE-ELECT.(WM526), CUMMINS BEFORE 1994

Part numbers for item in the 1994 model years

WM350825 C 86 TREADLE-ELECT.(WM526), 28.5 DEG CUMMINS AFTER 1994

WM350826 D 86 TREADLE-ELECT.(WM526), 35 DEG CUMMINS AFTER 1994

WM350827 A 86 TREADLE-ELECT.(WM526), 45 DEG CUMMINS AFTER 1994

WM351314 B 92 ELECTRONIC CONTROL (WM526), CUMMINS,DDEC 3 W/IDLE VAL/SWTC(This control is made for Cummins engines requiring the Idle sensor switch built into the Throttle) .

Rich.

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