Engine/Transmission (1998.5 - 2002) P0121

[ceastmen]

P0121

Accelerator Pedal Position Sensor Signal Volts Do Not Agree w/Idle Validation Signal.

Is there a way to adjust the TPS to get rid of this code? I've seen pictures of the TPS and it appears to be slotted allowing some sort of adjustment.

My truck runs fine except for these codes P1693 / P0121.

Thanks in advance Chuck E.

 

[AKAMAC]

There is a set of instructions floating around that explain how to calibrate the APPS. I think it was by DTT the transmission guys. Try a search..... Maybe Klenger or one of the other "resident holders of knowledge" will notice this post.

 

[DavidC]

Okay, This is per DTT



RESETTING THE APPS SENSOR.

(ACCELERATOR PEDAL POSITION SENSOR)

2ND GENERATION 24 VALVE TRUCKS ONLY.



LIST OF TOOLS NEEDED



DIGITAL VOLT METER

# 20 TORQUE BIT SOCKET

# 1 PHILLIPS

# 10 MM SOCKET



Proper service and repair procedures are vital to ensure personal safety of those performing the repairs. Standard safety procedures and precautions should be followed at all times to eliminate the personal injury or improper service, which could damage the vehicle or compromise its safety.

Although this material has been prepared with the intent to provide reliable information, no liability is assumed in reliance of this material.



It has come to my attention that a lot of people think by disconnecting & re-connecting the batteries and stepping on the throttle it is going to reset the apps, no, that is not correct. It is impossible to adjust your apps if you do not know where it is supposed to be set at. That is why you need the voltmeter.



This is the procedure I use to re-set the apps.



With the key on, engine off you need to probe the apps wire to see where your voltage is currently set at.

The best location to probe the wire is on the PCM (power control module) which is located off the passenger side of the firewall.



· You want the C1 connector, this is the connector closest to the engine,

· You want the orange wire with the dark blue tracer which is pin # 23

· Voltage should read somewhere around 0. 5 volts,

· At this point the voltage reading does not matter, it just has to be accurately written down for later reference.



*** TURN THE IGNITION OFF ON THE TRUCK ***









Resetting the APPS Sensor cont. page 2

(Accelerator Pedal Position Sensor)

2nd generation 24 valve trucks only.



· The apps sensor is located slightly above and a little to the left of the injection pump.



· Remove the black plastic cover that is located by your injection pump.



The two screws that are holding it are plastic, do not put any downward pressure on them or you will never get them off.



· Un do the 6 - 10 mm headed bolts that hold the bracketry in place.

(DO NOT REMOVE THE CABLES)



You will notice the apps is on the back of the bracketry that you just removed, it is held in place by 2 - 20 bit screws. These screws have a little bit of locktite on them so make sure you have a good socket and gently give a little tap with a hammer before attempting to loosen. Be very careful these screws strip very easily and you only get one shot at them.



· On the apps you will find a white tag that gives you the information on what the apps adjustment should be.



· After loosening the screws you can rotate the apps both clockwise and counter clockwise to get the adjustment you need.



· The reading you took at the beginning of the process on pin # 23 should match the white tag on your apps, if not adjust accordingly.



Dave