Cruise control has gone crazy

[GaryC 2001]

2001 Qd cab 6 speed cruise has went erratic surges horribly just started all at once no previous problem my old vp44 has been having some issues so I blamed the cruise issue on how ever VP was replaced this weekend all issues resolved except cruise any idea much appreciated

 

[Killer223]

Is it vacuum? I can't remember.
else check your alternator for AC noise.

 

[GaryC 2001]

Is it vacuum? I can't remember.
else check your alternator for AC noise.

No it has no vacuum servo it is all electronic

 

[hcole]

https://www.turbodieselregister.com/threads/258960-Mild-Surging?p=2514225#post2514225. See post #6

 

[gtwitch]

Cruise will not work if vacuum is not there!!! Look at the tee in the vacuum limne just above the starter at the firewall just below the windshield, I had mine come loose there a couple of times and the heater will not work and the cruise and 4X4 also fails to go in. Mine is a 99 also.
gtwitch in wyoming

 

[GaryC 2001]

Thanks for the input GT but mine is not vacuum controlled except for a hand full of early 2001 the 01's and up are all electronic

 

[GaryC 2001]

Thanks hcole I will give them a better look would be nice if it was as easy as that

 

[Bob4x4]

Diesel powered trucks built after June of 2000 have ECM controlled (servoless) cruise control. MTX equipped trucks built in June of 2000 and earlier (and all ATX equipped trucks) have PCM (JTEC) controlled vacuum servo operated cruise control.

 

[Bob4x4]

This is a case where using a drb 3 will make your life much better.You can monitor what is happening and why

 

[LorenStrodtman]

My 2001 (build date of February, 2001) sure seems to have vacuum controlled cruise control. Or at least it would if it worked! It doesn't work, hence my finding this thread in a search. Maybe that portion of my truck was built and leftover from before June, 2000.

 

[diesel DOG]

Mine is 2001 with vacuum.

 

[Missouri Mule]

I take it your only surging in cruise. And as I recall they did away with the pcm in 2000 or 2001 so the ecm should control cruise/speed control. The ecm should receiving data from speed sensor, gear sensor or rpm data ( probably won't go into cruise unless your in 6th. Also you could be having problems with the controls. But it seems I have read that sensor for the brake can act up. Caused maybe by brake switch slnce your 2001 is up there in years or loose wire coming from the brake switch to econ or cruise contol.

 

[Shelby Griggs]

The speed sensor on top of the rear differential can cause issues with cruise, I replaced mine a while back for cruise and I think ABS issues, can't remember the exact symptoms I saw, but I recall a couple things and the sensor fixed both of them.

 

[LorenStrodtman]

Thanks, Shelby, I'll add that to the list of possible solutions to my problem.