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I have a 2005 dodge ram 3500 cummins srw with 225000 kms. I have bean having intermittent

dead pedal and p2121 codes....
I have a 2005 dodge ram 3500 cummins srw with 225000 kms. I have bean having intermittent dead pedal and p2121 codes.
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Answered in 11 minutes by:
8/11/2012
Ricardo Hohl
Ricardo Hohl, Master Certified Tech
Category: Dodge
Satisfied Customers: 4,304
Experience: Automotive instructor at Porter and Chester institute
Verified

ricardo hohl :

Hi, you have a pedal position sensor problem not corrulating with the computers data.


 

ricardo hohl :

you have an electronic throttle that uses 2 throttle position signals to identify its position to the computer for diesel delivery to the combustion system one increases in voltage and the other decrease in voltage as you press the pedal the computer looks and the increase and the dcrease on voltage on both and should be sinchronizing together.

ricardo hohl :
Customer:

Ok, what should I be looking for to correct this issue.

ricardo hohl :

one loosing voltage and the other gaining the voltage the other sensor is dropping.


 

ricardo hohl :
ricardo hohl :

you will need to test the voltage drop and increase voltage of both sensors and this can only be done with a scanner.

ricardo hohl :

either sensor is out of limits.


 

ricardo hohl :

this can be a bad conection at the throttle also.


 

ricardo hohl :

check the conector make sure there is no corrution on the electrical pins inside the conector.


 

Customer:

You type faster than me, you keep answering my questions before I can type it. LOL

Customer:

ok where is the sensor in the engine compartment

ricardo hohl :

yes one is at the throttle in the engine compartment and the other one is at the gas pedal inside the drivers compartment it looks like a brake switch.


 

Customer:

yes I'm familiar with the pedal end. Is the throttle in the pump?

ricardo hohl :

Full Size Image


 

ricardo hohl :

the throttle is at the air intake


 

ricardo hohl :

The Accelerator Pedal Position Sensor (APPS) (1) is located inside the vehicle.
It is attached to the accelerator pedal assembly (3).




ricardo hohl :

The Accelerator Pedal Position Sensor (APPS) provides the Engine Control Module
(ECM) with two DC voltage signals which change as the position of the
accelerator pedal changes. One of the DC voltage signals will be half the
voltage of the other signal.


 

Customer:

ok I havent looked at the intake that closely. can the voltage be checked with a digital meter and witch wires?

ricardo hohl :

give me a minute let me see if i can find a pin out picture for you to follow.


 

Customer:

ok will fill my coffee cup

Customer:

back

ricardo hohl :

ok this is the wiring schematic between the computer and the electronic throttle at the intake, i will send you also the conector view and its function so you can check for voltage.


 

ricardo hohl :

Full Size Image


 

ricardo hohl :

Full Size Image


 

ricardo hohl :

Full Size Image


 

Customer:

is there a certain procedure ie. depress pedal while checking etc.

ricardo hohl :

check the voltage between both sensors , while depresing the pedal see if


 

ricardo hohl :

 


the voltage transition shown on the scan tool smooth while depressing the
accelerator pedal and is the voltage from APPS 1 twice as much as the voltage
from APPS 2?

Customer:

ok

ricardo hohl :

this can be hard to do with a multimeter thats why i say you need a scanner to be able to see both voltages at the same time.


 

ricardo hohl :

you will also need to mesure resistance at the sensors let me send you that also.


 

Customer:

Just to add. last weekend I was towing my rv trailer and almost had an accident because of this, since then (having done nothing) I haven''t had any problems. It's very frustrating.

ricardo hohl :

i understand the pain belive me i see this every day in here with the electronic throttle bull the factory invented in stead of staying simple with the throttle cable.


 

ricardo hohl :

Measure the resistance of the APPS 1 supply circuit between the APPS sensor
connector and the ECM connector.


 

Customer:

ok thanks. I have two meters. The scanner you refer to is the dodge one that costs about $5000??

ricardo hohl :

correct .


 

ricardo hohl :

we can do with two meters is ok.


 

Customer:

For $5000 I could probably have the dealer figure it out

ricardo hohl :

make sure the resistance less than 10 ohms?


 

Customer:

Cool, all great info so far. do you know if I can print this conversation?

ricardo hohl :

Full Size Image


 

ricardo hohl :

if there is hi resistance then you have a wiring problem.


 

Customer:

wouldn't surprise me I've had to repair the dr side pass door harness before

ricardo hohl :

very good some knollege is always welcome it makes my job easier, and as i see you know what you are doing .

ricardo hohl :
Customer:

I hope I find a bad wire. I have replaced the pedal 3 times trying to keep the truck drivable

ricardo hohl :

if the resistance is ok, then follow the next step


 

ricardo hohl :

Measure the resistance between the APPS 1 signal circuit at the sensor connector and battery negative.

ricardo hohl :
Customer:

okThe dealer seems to just want to replace the pedal again rather than find the cause

ricardo hohl :

thats just gessing and that can be expensive unless its warrenty then who cares right?


 

ricardo hohl :

thats call a shot gun repair .


 

ricardo hohl :

going back on the last info.Measure the resistance between the APPS 1 signal circuit at the sensor connector and battery negative.


 

Customer:

Yeah, thats the problem. I can't afford to pay the dealer to diagnose this. I spent $600 last month and still have the issue

ricardo hohl :

it should be not greater than 100 K ohms.


 

Customer:

Great this is the kind of info I've been looking for. It's fine to check wires but if you don't know limits you could miss the problem

ricardo hohl :

let me know what you find ,if no problems found with the sensors and wiring then replace the electronic throttle.


 

Customer:

Is there a way I can get back to you?

ricardo hohl :

yes just save the page and open it again when you have resolts i will leave the question open.


 

Customer:

Thanks

Ricardo Hohl
Ricardo Hohl, Master Certified Tech
Category: Dodge
Satisfied Customers: 4,304
Experience: Automotive instructor at Porter and Chester institute
Verified
Ricardo Hohl and 87 other Dodge Specialists are ready to help you
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Customer reply replied 5 years ago
OK, Voltage @ Sig # XXXXX is 0.45 v @ idle & 4.56v @ full Th. V @ Sig # XXXXX is 0.22 v @ idle & 2.27 @ full Th.
The Voltage seems to transition smoothly and is within a couple hundredths of a volt of the 50% mark.
It did throw a code for P2127 but it was as I connected either sensor with key on ( no code with lead connected before key on).
Voltage @ both supplies were 5.03v each.
I could not find a throttle sensor on the intake so all connections were made at the pedal connector.
Resistance measurements between pedal and ECM connectors: (range scale 200) 5v supply 1.5-0.5R, APPS #2 Sig. 0.0R, APPS #2 return 1.5-0.5R, APPS # XXXXX return 33.0R, APPS #1 Sig. 0.0R, 5v supply 0.0R.
The resistance of Sig. # XXXXX @ pedal connector and battery ground is 7.8R on 20K scale and 9.9 on 200K scale???

ok it seems like pedal position sensor is out of range it should be consistent to pps#1 PPS#1 IS AN EXCELENT READING PPS#2 IS NOT GOOD NEEDS REPLASING THAT IS THE PROBLEM.
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Customer reply replied 5 years ago
so that's the sensor on the pedal? Or a different one. Is there something causing the sensor to go bad? I have replaced 3 times, basically every year since I bough the truck.
yes thats the sensor and yes it does go bad because its in constant use every time you step on the gas , just make sure when replacing is new and from the dealer
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Customer reply replied 5 years ago
Is APPS #2 part of the same sensor? Witch reading on PPS# XXXXX voltage or resistance?
and what about the resist on Sig #1 to ground Is that not 7800 Ohms? you said no more than 100. Am I reading it wrong?
I can't believe that I am the only one I know of that has to do this. Friends with same truck have no issues. Oh so frustrating.

yes it is , they may not have an electronic throttle as yours does, there are no TSB from the factory stating any fix to this problem, they do have a flash programing to the electronic throttle but they will not disclose the procedure this is something you will need to ask them as you bye the part. make sure the connector is fully seated and secure, make sure your battery is in good condition check the battery terminal wire for a good ground to the engine, make sure the alternator is charging well, this are all the posible points that may affect pps#1 and #2 operation and duration.

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Customer reply replied 5 years ago
OK thanks for your help. I have a new part already, they can be hard to find. I have not been able to by one in Canada yet, always find in the US.Are the new Rams the same? Not cheap but a good fix.
well they are having transmission problems and power distribution problems but not throttle problems i guess they took the bugs out with an upgraded throttle control., no problem it was great working together with you, very good at electrical and using meters, i was very impress. thank you.
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Customer reply replied 5 years ago
Cheers!!
By the way, is there a way to change the heater core without discharging the A/C on this truck. My next project!

no you have the remove the heater box out and the evaporator is there sorry you have to evacuate.

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Ricardo Hohl
Ricardo Hohl
Ricardo Hohl, Master Certified Tech
Category: Dodge
Satisfied Customers: 4,304
4,304 Satisfied Customers
Experience: Automotive instructor at Porter and Chester institute

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