I am working on a 98 24v auto.The throttle is very erratic and the trans shifts very fast.Have tried a new apps no change.When driving at part throttle the power is very low and as you increase the throttle to about 1/4,the truck feels like its running away.When you take off the trans shifts into 3rd gear before you reach 20 mph.It will buck and jerk right where it starts to run away.Only codes are p0501 and p1693 and no MIL.When you lockout od,the power drops to nothing.Speedo works fine.Any input greatly appreciated!

 

the problem sounds like a bad APPS sensor.. (throttle poisition sensor).. they can become out of wack... there is a trick to reset them.. but it might be time to replace it

 

http://www.bluechipdiesel.com/vp44_diagnostics.html

Go to this link and scroll down to the red writeing where it is talking about erratic throttle, this has alot of good info on how to find the issue

 

RPM GOES UP ON ITS OWN, OR WAIT TO START LIGHT IS DUMB, OR THE SUPPLY VOLTAGE TO THE APPS AND MAP SENSORS IS ERRATIC OR OUT OF RANGE, OR YOU HAVE DELAYED 12V POWER TO THE LIFT PUMP AND INJECTION PUMP, OR YOU HAVE A 606 CODE

This is actually what the red writing says, hope it helps

 

Sorry for the slow response!I fixed this truck and you would not believe what I found.Turns out the truck had a '01 engine and ecm installed at some time.It kept setting the p0501 which is a speed sensor rationality code plus the p1693 compaion code.I found that the cmp wiring had been overlayed from the original harness because of different pin positions in the connector at the ecm.Apparently the '01 ecm has different pin positions than the '98 ecm.It also had a speed signal wire that was supposed to go to pin 43 but the '98 evidently didn't use this circuit because there was a plug in the pin hole of the connector at 43.I found the white and orange wire at the CAB module and tapped into this wire and ran it to the ecm connector pin 43.I cleared the codes and they didn't come back.I test drove the truck and it ran perfectly.The customer was amazed and very thankful because he had taken the truck to several different people and spent many dollars throwing parts at it and had the same results every time.Just thought I'd let you all know what I found in case someone ran into the same problem.I was beginning to go bald trying to figure this one out!!!!Thanks for the help!