Engine/Transmission (1994 - 1998) Cruise control not working; 1996 12v auto trans

[GAmes]

The service manual doesn't show a procedure to test the low vac sensor(at least not that I could find)

Does the info on page 8W-34-2 help?

 

[Texis]

I believe the problem lies in the low vacuum sensor as detailed on other TDR threads and elsewhere.

After I finally decided to replace my servo and the cruise started working, I found an OPEN vacuum line at the discontinued CAD location. Hose was completely off the metal line that is on the frame. Moral of the story is even with a vacuum line completely off, the cruise still worked. Food for thought.

 

[Solar1]

Does the info on page 8W-34-2 help?

Hello GAmes,
i does help a little, looks like pin 1 should be grounded, pin 3 should be 12 volt with key in on position, but i'm not sure how pin 2 works.

i'm wondering if i can use a jumper from the vac sensor (pin 2?) to ground to trick the system(bypass low vac switch?

I'm in a little over my head right now, but with a little help, I may understand it.

Well, I also read it could be a faulty CAB module.

 

[GAmes]

It appears to me that pin 2 is a power wire to activate the dash light and the CAB (which I believe de-activates ABS). Rather than ground it, I am of the opinion it should be cut (disconnected) since it only sends a signal if there is a problem..

 

[Solar1]

It appears to me that pin 2 is a power wire to activate the dash light and the CAB (which I believe de-activates ABS). Rather than ground it, I am of the opinion it should be cut (disconnected) since it only sends a signal if there is a problem..

i was thinking about something like that idea, but then, wouldn't the light go out if i just unplugged the sensor? it does not.
Today, for lack of access to a drbIII tool, i'm going to try to check the rear speed sensor at the differential.

 

[GAmes]

If everything else in the system is working I believe that disconnecting the #2 wire would turn off the light. You don't need a DRB, you can access fault codes using the ignition key on/off sequence. (page 25-4)

 

[Solar1]

If everything else in the system is working I believe that disconnecting the #2 wire would turn off the light. You don't need a DRB, you can access fault codes using the ignition key on/off sequence. (page 25-4)

thanks much, i'll try that, never knew that, i thought i needed the scan tool.

 

[johnjackson]

Brake light and harness connection at top front of engine that goes to sensor at damper pulley. At least those are the two things that stopped my cruise.....John

 

[KRStone]

Given the connector resembles:

+------------+
+ -  -  -  - +
+   +
+   +
+------------+
   | |

the hypens inside the 'box' are the pins, number 4 to 1 (left to right).

• Pin 1: vacuum, increase speed
• Pin 2: vent, decrease speed
• Pin 3: +12VDC
• Pin 4: ground

1. Jumper +12VDC and ground to pins 3 and 4, respectively.
2. Start engine, leave in neutral or park.
3. Momentarily (and I *do* mean momentarily: a millisecond is too long) jumper pin one to ground. The engine speed should increase. Do it a couple times to get the engine up to maybe 2500 RPM.
4. Momentarily jumper pin 2 to ground. The engine speed should decrease. Do it a couple times.
5. Disconnect pin 3 to return to idle.

My CC hasn't worked in years. I did this to verify that the servo was in good working order. My problem is elsewhere. Prolly in the PCM, possibly in the steering wheel (the switches connect different resistances to the PCM which is how the PCM know which switch was pressed)

Is your diagram the harness plug, or the servo itself?
And it is 4 on the left, and pin 1 on the right?
When you say touch to ground, do you mean truck ground or the ground pin on the servo?

 

[johnjackson]

If your tachometer hick ups once in a while it is the harness connector at top front of engine. Hard to get to as it is under top hose and attached to a tab. Unplug and re-plug it a couple times and see if cruise works. If so clean both sides of connection and apply dielectric grease. Worth a try maybe. I go from CA to MT every year and would be miserable without cruise.

 

[KRStone]

Pulled the servo out, cleaned up the little bits inside following the video on u tuube.

Oiled the metal parts that move.

Found another hole in the vacuum line, fixed it.

Test drive = SUCCESSFUL.

Thank you for the help, glad it is working again and it didn't cost money to fix.

 

[Texis]

Glad the servo re-do worked for you. I did that a couple of times without success. Took a new servo to fix mine. If you travel much, life without cruise is terrible!

 

[KRStone]

I have driven from southern AZ to idaho several times, no cruise. Glad to have it working again.