Engine/Transmission (1994 - 1998) Another Cruise Control Problem

[LHallmark]

This Rotten-Ratch-A-Fratch... ... :-{}

Cruise quit a while back... ... When cruise turned on, light comes on and after 20 sec it goes out. This causes multiple engine starts to accomplish the troubleshooting... ...

Pulled out service manual... found switches in steering wheel bad(Ohms check), so replaced them. NO FIX... I even measured the switch continuity from the PCM plug and the wiring checks good. .

Did the voltage and ground checks to the speed control servo... ...

With engine and Ign off I have a good ground at pin 4 of the wiring harness.

With engine running I have 13. 7 volts on pin 3 of wiring harness, apply brakes and 13. 7 volts disappears. With pin 3 of the wiring harness jumpered to pin 3 on the servo I have 13. 7 at pin 1,2, and 4 on the servo. Vaccum measures 25" hg at the servo.

Everything checks good in accordance with the service manual. :{ :{



Do I have a PCM problem in the speed control circuits? Everything else works OK... . AC, TACH, OD Shift, TC Lockup, etc. I strongly suspect the PCM since the cruise light goes out... . which suggest a voltage loss.



What is your thoughts????



HELP! HELP! I have pulled so much hair out I'll soon be bald... ...

 

[K5IP]

Are you sure the tach works ok? enen a slight, hardly noticable glitch in the tach output can cause a cruise control drop out. Watch the tach very closely when it drops out. If you see any movement at all, check the connector from the crank speed sensor. This seems to be a reoccurring problem.

Rog

 

[LHallmark]

K5IP... . Thanks for the tip. Checked it all again, both the VSS and CPS are good. The thing that bothers me most is once the on switch is pressed and the pwr light comes on... . then in a few seconds the light goes out!! That indicates a loss of pwr... . either a voltage source or ground. The grounds are good(checked by meter) so I strongly suspect the PCM is taking the voltage away. The big question is WHY??????



Again thanks for the reply and the tip... ... . Lance

 

[K5IP]

Lance,

Yes, now that I read your info better, I see that you have a different problem than I had. My cruise light stayed on but the system dropped out. Sorry I can't help but I'll look through my manual and see if I can figure out where the light power is sourced. Perhaps that will get us started in the right direction. If I find anything out I'll post again.

Rog

 

[EB Diesel]

I had a problem after 3 years - dealer checked everything except the servo - lo and behold after I remided them the second time to check it that was the problem. Also since the I had a reocurring but not constant problem with the cruise and I disconnected the batteries for a couple of minutes and everything re-set to normal

GOOD LUCK!!