Recently my truck has had shifting issues with 1-2 upshifting. I did the whole governor pressure/ shift selenoid, filter/ oil, TV cable adj, new alternator, noise suppresor on APPS wire at pcm, re-routed ground wires around alternator, tested battery life, and now replaced the APPS Sensor itself. No codes were present before i replaced the sensor. The new sensor now shows a code P0122 ( low APPS sensor voltage) but it still works and gives throttle. Truck still shifts bad after front and rear band adjustment. Revs to 2,000 RPM and wont shift unless you let off the pedal a bit and get back on. I am running out of things to replace, does anyone have a point of direction on where to head next. Im going to get mulimeter numbers tomorrow...snow permitting. Sorry for the long post wanted to include everything. Thanks Guys!

 

Verify you have five volts on the Dark Blue/white wire with ignition on. Black yellow should be ground. Light Blue/Black wire should start out with very low voltage, (less than 1) and climb to greater than 3.5 at wide open throttle.

(connector plugged in.....)

 

Thank you for the reply. With the Key on and connector plugged in a tested the plug at idle and full throttle. I have a six wire connector on my truck. The following are my results.
Color Idle Full throttle
White .01 .01
Yellow 4.70 2.96
Blue 4.69 4.68
Red 5.04 5.04
Green .35 3.95
Black .01 .02

My new sensor does not have oblong holes to adjust preload on the APPS. I have a torx screw on the bell crank that controls the resting position of the throttle cable.

 

Sorry for the interruption but is the APPS sensor just a diesel thing?

 

Hhhmmmm.... The wire colors you have don't correspond to what the service manual is showing should be there...... In any event....

Pin 1: Ground for idle validation switch circuits.
Pin 2: Should be around 5 volts. Supply for IV switch 2. (there are two....)
Pin 3: Signal return from pedal position sensor. Value should go up as you press the pedal.
Pin 4: Sensor ground.
Pin 5: 5 volt supply to PPS.
Pin 6: 5 volt supply to IV switch 1.

The supply circuits should always be right around 5 volts, regardless of pedal position. I think the code is whining about the position sensor itself though, getting a low voltage signal. (when it thinks it should be higher...) If the green wire is in Pin 3, then that part is working as it should, and I would suspect either a break in the wire, or, a failing PCM. Check the wire AT the engine control module, pin 25. See what you are getting there.

Yup.

 

Thanks for the guidance. I pursuit of chasing these electrical gremlins. I pulled the pcm connection closest to the engine and checked voltage at pin 25. There is no pin in my connector for 25. Voltage at pin 23 is .31VDC and pin 22 is 12.37VDC if that means anything. I am assuming if there is no pin in the connector, that particular one is not used?? I included a pic as well.....I am determined to squash this gremlin...I doubt the transmission itself is to blame.

 

No wire at pin 25? That's strange.... Does the signal wire go to a different cavity in the connector?

Also, the ground supposedly goes to pin 32.... but, I don't SEE pin 32 in the pic..... 31 appears to be the last one??

 

IIRC, the connectors go A-B-C, starting from the drivers side to outboard/passengers side.

 

So after making a call to BD Diesel where I got my apps noise issolator the orange wire with black tracer is the supply wire for the APPS sensor and on my truck it goes to pin 23 for some reason. At that pin I am reading .31 VDC. The new APPS sensor does not have a tag on the back like the original one to match set the required voltage. I re-checked the grounds and cleaned the connections. I did notice that both my battery terminal connections are in pretty rough shape, now I am wondering if and small voltage interruptions at the battery would affect my shifting/APPS signals at the PCM. No other systems are experiencing any flukes. Thats where I am at as of now...

 

Clean the battery terminals and see. I know the gas engines can exhibit some truly bizarre behavior if the electrical system is even slightly marginal.