Cruise Will Not Set

Just started happening last week. Installed cruise with JY parts. Worked PERFECTLY for a few weeks then just decided it had enough. I can turn the system on and off and the light on the dash will light up. That's as far as it goes. I have the FSM AND the Powertrain Diagnostic Manual. Here's what I know so far:

-I can turn the system on and have 12V from the PCM to the brake light switch (yellow/red wire)
-There IS continuity from the brake light switch to the servo plug (blue/red wire)
-with the brake light switch plugged back in, installed and system turned on, I only get 0.2V at the servo plug instead of 12V at the brake light switch
-My ground for my servo is good
-Both my wires from my servo to my PCM are good (tan/red and green/red)
-New brake light switch, tested as per the FSM and it's good
-tested (as per the FSM) the old servo as well as a new one from the wreckers just in case and both check out
-took it to the dealer, they "apparently" did the full diagnostic ($55) and told me the servo was shot and $260 would get me a new servo plus installation.....told them to forget it

SO......I'm kinda stumped......I've gone over every possible wiring diagram I can think of and nothing seems to work. It's a bit annoying cuz I finally got used to having cruise and now I'm back to not having it at all and kinda want it back Any suggestions?

The servo is shot?

where can I find the FSM? Mine won't work either. Light on dash just comes on.

heyjpark1 said:

The servo is shot?

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that's what the dealer said but both mine and the other one I got from the wreckers tested fine using the book method as well as when installed in another XJ they both work......not the servos

jeepster_259 said:

where can I find the FSM? Mine won't work either. Light on dash just comes on.

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I went on eBay and got a copy for pretty cheap. You can also order then new from TechAuthority (can't remember the exact address but you can Google it I'm sure) You can also get a copy on CD from them as well.

check for a cracked vacuum line near the battery

jneary said:

check for a cracked vacuum line near the battery

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X2 on that recommendation. Not saying that it is a vacuum problem but many cruise problems are and they are often overlooked.

I'm gonna pull my bumper off tomorrow and start from the canister and work my way back....hopefully it's something simple like that and now a new computer

I have no idea if this even applies to your situation, but I'll throw it out there. I recently bypassed my NSS switch and surprisingly found that my cruise would turn on, but not set.

After I have replaced my NSS, the cruise will now set.

Maybe a quick cleaning of your NSS wouldn't hurt. I was suprised that the trans was sending a signal to the cruise, but maybe it is a safety thing.

My 90 has the same problem....vacuum engages the servo and maintains the speed. HIGH up on the brake pedal arm, there is a white switch, it releases the vacuum when you are in cruise and tap the brakes. It also unlocks the torque converter to allow the car to coast. So this switch has an electrical and a vacuum function. If it is bad or is out of adjustment, you will not get vacuum to engage cruise.
the switch is WWAAAYY up high on the brake pedal and is a pain to see, much less get to. Good luck.

troy said:

I have no idea if this even applies to your situation, but I'll throw it out there. I recently bypassed my NSS switch and surprisingly found that my cruise would turn on, but not set.

After I have replaced my NSS, the cruise will now set.

Maybe a quick cleaning of your NSS wouldn't hurt. I was suprised that the trans was sending a signal to the cruise, but maybe it is a safety thing.

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Welll....this may be the problem....I know for a fact my NSS is hooped because I have no reverse lights and it'll only start in Park.....awhile back, I got a few codes regarding the NSS so I think it's finally time to pull it off and clean it.....hopefully that'll sort the problem out....

I have a similar problem on my 98XJ my rverse lights quit working and my cruise lights up but doesnt hold. Put a new NSS about a month ago and everythng was fine untll a week ago. All fuses are fine. Stumpped