Cruise control/ vaccum bottle

Can not having the vaccum bottle connected to the cruise control keep the cruise control from working?

I have swapped in a new cruise motor/acuator, and cruise still doesnt work. My truck never has had a vaccum bottle, and currently im looking for one. What else could my problem be?

cody4359 said:

Can not having the vacuum bottle connected to the cruise control keep the cruise control from working?

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Since the cruise control module is vacuum operated, that certainly would cause it to not work.

Well, your rig must have had a vac bottle at some point.

What year?

Do your climate controls function on vacuum or electric actuators?

On my 89 I have found that the brake light switch is usually the culprit and has disconnected or frayed wire at connector.

Also, the switch on the turn signal has gone bad once or twice and is troubleshooted with an ohm meter.

Junk yard switch is a good replacement.

Remove old turn signal lever by pulling straight out of column with wipers in off position and no turn signal position.

NOTE- Tie a string to the old wire connector under dash before you pull it up thru the column.

Use the string as a fish tape to install the new wire down the column without tearing apart the whole thing.

It can make it act real funky... that's for sure.

Know anyone with one that you can borrow? I usually reroute the line to it and stuff it down over the oil filter if I've got an aftermarket bumper on the jeep.

cody4359 said:

What else could my problem be?

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In addition to vacuum, on some, a broken clockspring can also keep it from working.

Thanks for the replies. The truck is a 87 mj with a 00 wj motor. PO slapped it together, and i have slowly been trying to make it nice.

ill try the vaccum bottle and ill have to dig into the clock spring, horn doesnt work either.

cody4359 said:

Thanks for the replies. The truck is a 87 mj with a 00 wj motor. PO slapped it together, and i have slowly been trying to make it nice.

ill try the vaccum bottle and ill have to dig into the clock spring, horn doesnt work either.

Click to expand...

No clockspring on an 87. Just get the bottle on there.

Ya im going to give that a try bit ill still have to dig around on the horn issue. Its an 87 mj, 00 wj motor, and 97+ conversion.

I wonder how the hell he did the electrical system? What steering column is in use? Was the harness modified between the ECU, clockspring, and cruise control modulator solenoid?

Its a 4.0 so 97+ engine wiring works. Im guessing the wiring harness is 97-99. Fuel tank was a 97+ xj unit mounted behind the axle where the spare tire goes. Only splicing to the mj harness was for the taillights. Interior has all been swapped.

Any chance you can get the part number off the ECU and the part number, or revision code, off the cruise control switch panels? They'll be 7 or 8 digit part numbers followed by two-letter revision codes. The ECU is probably P5604 and then (in bigger lettering) 3 numbers and two letters, the switch panels will be AB, AC, or AD revision code afaik. Between 98 and 99 they switched the resistance of the switch panels and only changed the revision code, and using an ECU from one side of the split with switch panels from the other side results in no cruise function. Fortunately it's as simple to fix as swapping to the right year range/revision code switch panels.

Reminds me, when you push the buttons does the cruise indicator on the dash come on? If it comes on, the wiring from the ECU to the cruise switches is functional and the switches and ECU are from the proper year ranges, and you have a brake light switch / vacuum / vacuum solenoid / vacuum solenoid wiring issue. If it doesn't come on, you almost certainly have an electrical issue between the ECU and the cruise switches, OR the ECU doesn't want to go into cruise mode for some reason, I know when I had a blown head gasket in my 98 that was resulting in a set CEL and/or flashing CEL, it often would refuse to turn cruise on.

Ecu is P56041 493AE


Where do i look for the cruise control? I didnt see any codes on the unit i put in or the one i pulled off. No, when i press cruise control, no light comes on in the cluster. Damn, never easy

That actually makes it easier... check engine light on? If not, it's almost certainly the wiring between the ECU and the switches on the wheel.

P56041 493AC is the closest ECU part number I have (probably just a firmware upgrade between AC and AE) and it comes back as a 1999 XJ, ER0 (4.0L) engine, DG0 (AW4) transmission, California emissions control system. So you would want a set of cruise control switches part number 5600 7530AD and 5600 7531AD to go with that ECU. Revisions AB and AC are for 97/98 years, AD is for 99-01. The AC rev seems to be a minor improvement not an actual change from the AB rev, since they didn't mark it as a new part, while the AD rev is marked as a new part incompatible with previous years or requiring other changes to install.

If the switch panels you have are AD revision code ones, you probably have a wiring issue or a bad clockspring. Fortunately the wiring is simple - it's basically two wires that go all the way from the switch panels at the steering wheel to the ECU by way of a few connectors and the clockspring, so you can easily check continuity after looking in the factory service manual (for a 1999, it seems) for the right pins to check against at the ECU.

If the switches you have are AB or AC revision, you SHOULD be able to just swap them out for a set of ADs and it will work, unless you have other issues as well. I'd recommend installing a vacuum canister for testing purposes.