da_jokker
NAXJA Forum User
- Location
- N California
About a month ago, my cruise control stopped working. I've been using it constantly since I've owned the XJ (about 2+ years) without issues.
It seems that the common cause is Vacuum.. so I did some checking and what-not and pretty much ruled that out. Primarily based on 3 things...
1) Everything else that uses Vacuum works fine (AC/Heater controls)
2) After leaving the XJ off for 30+ minutes, I can disconnect the vacuum line at the servo and hear the air sucking in.
3) Doing the Computer error check, it is reporting code 34 which maps back to some sort of Electrical Current issue.
With that in mind, and noticing that my Cruise Multi-function switch was really worn and the buttons seemed a bit "questionable"... I figured for $14, what the heck so I ordered one up and after about 15 minutes, had it installed.
Still, the cruise did not work. What I'm noticing is that when I first turn it on and attempt to use it, it will work 70-80% of the time. But after using it for a couple minutes, it just disengages and won't come back on. Next day (or sometimes even after coming back out of the store), it will work again 1 time only and for a very short distance.
Doing further research, I found a tech article that talked about how to test the Servo....
Using a Multi-meter, I tested the voltage at the servo... I would get 12v when the Cruise switch was on... 0v when it was off. In addition, the resistance for the ground was 0 ohms.
The article then suggested testing the server by applying 12v to a pin (#2 IIRC) and then ground the other 3 pins. Then, apply some vacuum to the Servo and the throttle cable should move... when I did this NOTHING. The Servo held the vacuum for as long as I wanted it to (using a hand pump). I could hear something inside it clicking when I applied the 12v... but nothing moved.
So figured that was my issue. $30 and 20 minutes later, I had a new servo in.. and obviously had that solved my issue, I wouldn't be writing this.
So here is what I think I know...
1) Cruise will come on briefly, sometimes. So it seems like that would rule out a blown fuse.
2) Brake light switch was replace 2 years ago (due to brake lights not working). They are currently working correctly (Pedal = On, No Pedal = Off). And I've held the pedal up with my foot while driving just to be sure and still no workie.
3) ECU reports a Code 34 which suggest it is electrical
4) Multi function switch and Servo have been replaced (Not factory, but both are NEW and not from a junk yard).
5) Vacuum seems to appear good with everything else working and lines maintaining vacuum long after the engine is shut off.
6) Being it is a 89-96 model, according to Haynes, my entire Cruise Control is ran by the Switch, Server, and ECU. I'm not supposed to have a Speed Sensor like the 84-88 models. (However there is something right near the throttle pedal hooked into what looks like the spedo cable... not sure what that is)
Not sure if I left anything out but I'm at a loss.
It seems that the common cause is Vacuum.. so I did some checking and what-not and pretty much ruled that out. Primarily based on 3 things...
1) Everything else that uses Vacuum works fine (AC/Heater controls)
2) After leaving the XJ off for 30+ minutes, I can disconnect the vacuum line at the servo and hear the air sucking in.
3) Doing the Computer error check, it is reporting code 34 which maps back to some sort of Electrical Current issue.
With that in mind, and noticing that my Cruise Multi-function switch was really worn and the buttons seemed a bit "questionable"... I figured for $14, what the heck so I ordered one up and after about 15 minutes, had it installed.
Still, the cruise did not work. What I'm noticing is that when I first turn it on and attempt to use it, it will work 70-80% of the time. But after using it for a couple minutes, it just disengages and won't come back on. Next day (or sometimes even after coming back out of the store), it will work again 1 time only and for a very short distance.
Doing further research, I found a tech article that talked about how to test the Servo....
Using a Multi-meter, I tested the voltage at the servo... I would get 12v when the Cruise switch was on... 0v when it was off. In addition, the resistance for the ground was 0 ohms.
The article then suggested testing the server by applying 12v to a pin (#2 IIRC) and then ground the other 3 pins. Then, apply some vacuum to the Servo and the throttle cable should move... when I did this NOTHING. The Servo held the vacuum for as long as I wanted it to (using a hand pump). I could hear something inside it clicking when I applied the 12v... but nothing moved.
So figured that was my issue. $30 and 20 minutes later, I had a new servo in.. and obviously had that solved my issue, I wouldn't be writing this.
So here is what I think I know...
1) Cruise will come on briefly, sometimes. So it seems like that would rule out a blown fuse.
2) Brake light switch was replace 2 years ago (due to brake lights not working). They are currently working correctly (Pedal = On, No Pedal = Off). And I've held the pedal up with my foot while driving just to be sure and still no workie.
3) ECU reports a Code 34 which suggest it is electrical
4) Multi function switch and Servo have been replaced (Not factory, but both are NEW and not from a junk yard).
5) Vacuum seems to appear good with everything else working and lines maintaining vacuum long after the engine is shut off.
6) Being it is a 89-96 model, according to Haynes, my entire Cruise Control is ran by the Switch, Server, and ECU. I'm not supposed to have a Speed Sensor like the 84-88 models. (However there is something right near the throttle pedal hooked into what looks like the spedo cable... not sure what that is)
Not sure if I left anything out but I'm at a loss.