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850 Cruise Failure

DavidSamuels

DavidSamuels

K-Jet-Free Zone
Joined
Nov 12, 2007
Location
Palmdale--Hi Desert, N of L.A.
Looking for an epiphany. Our '97 855 has lost it's cruise control. This happened when a rebuilt alternator's regulator failed and was overcharging. May be a coincidence, don't know. Once the alternator was repaired, the cruise no longer worked. I had been experiencing, for about a year, a situation where the cruise was slow to accelerate the car via the stalk button. It worked but was sluggish. Other than that, it was fine. In troubleshooting the failure, I found the pedal switch had one broken clip and was sitting at an angle. Hard to say if that was the sluggishness issue, but replaced the switch and I adjusted the plunger to the depressed pedal (running) by pulling it out per instructions and letting it self-adjust. The pump is tested good. Plumbing is good and the MityVac at the pump will pull the diaphragm all the way in. Have swapped the ECU for another. Pulled the column cover and confirmed there are no broken wires in that little bundle. No codes at all. Odometer and speedo working correctly, so I'm assuming the speed sensor on the trans is okay. What am I missing? Any help appreciated. Haven't found a good article to diagnose perhaps via the terminals of the cruise ECU. DS
 
vacuum leak

the brake pedal switch goes bad - I had a hard time adjusting my used one.. got another and it forked
the line in the engine compartment rubs through
the rubber cheese elbows that hold the vacuum line go out


ps I had the same issues as you did and found a vacuum leak where I didnt look before, then the switch went bad about 2 months later
 
Thanks Jack. Switch is factory brand new and I can pull a vacuum from all the way forward at the pump to the diaphragm and it's perfect. Holds vacuum and the pedal gets pulled all the way in. Gotta be something in the electrical/control setup.
 
I would try to get my hands on the documents from the factory and go diagnose the circuit.

A high level scan tool might reveal a code that could help. Or doesn't the 97 still have the blinky box too?
 
DavidSamuels said:
Thanks Jack. Switch is factory brand new and I can pull a vacuum from all the way forward at the pump to the diaphragm and it's perfect. Holds vacuum and the pedal gets pulled all the way in. Gotta be something in the electrical/control setup.
Click to expand...

Im trying to think of what was wrong with mine.. it was something stupid simple one time

check 1 and 17?

GR-60575.jpg
 
ZVOLV said:
I would try to get my hands on the documents from the factory and go diagnose the circuit.

A high level scan tool might reveal a code that could help. Or doesn't the 97 still have the blinky box too?
Click to expand...

only an oscilloscope works on the cruise control

97s do not have the diag boxes ... obd2 bro
 
^^^ This. One instance where I wish the blinky box was still here. Jack, Everything vacuum related is working. Pump pulls strong on the bench and will pull the diaphragm in if I jump power to it in the car. Wondering if the stalk switch is bad, but they don't seem to be problematic from what I've read. Thanks.
 
^^^Well without a diagnostic box for '97, most of it is not applicable, but there are some tests at the ECU base/plug I can try.

I see that Vol FCR has a cruise option. It's instructions on how to hook up an LED and push button to simulate the pre-97 blinky box. Guess it's not accessible via the OBD2 port. Ugh.
 
DavidSamuels said:
^^^Well without a diagnostic box for '97, most of it is not applicable, but there are some tests at the ECU base/plug I can try.

I see that Vol FCR has a cruise option. It's instructions on how to hook up an LED and push button to simulate the pre-97 blinky box. Guess it's not accessible via the OBD2 port. Ugh.
Click to expand...

There is a test procedure to jump the cruise control and see where the broken link is.
 
With a bidirectional scan tool, the right one such as VIDA, one could probably go in there and look at the data and maybe control the servo.

And a scope could be used to confirm a speed signal into the cruise control unit to verify the speedo is sending a signal out, son.
 
When I swapped my 850 to a manual, I had to replace/add a relay to get the cruise to work. Not sure if yours could have gone bad with what you say happened but here is the relay number: 1378076

Might be worthwhile to replace it. They're $15.
 
matt b said:
When I swapped my 850 to a manual, I had to replace/add a relay to get the cruise to work. Not sure if yours could have gone bad with what you say happened but here is the relay number: 1378076

Might be worthwhile to replace it. They're $15.
Click to expand...

Not really needed a second relay. A tab on the stock relay needed to be cut off to make the CC work on a manual swapped 850.
 
Harry is right, you can cut or bend over a pin on the stock module to make it work in a manual, BTDT.

Zach...no OBD connection to the cruise on Dave's car, unless you have a VST, which aren't easy/cheap to come by. Aftermarket stuff won't touch it, newer stuff won't touch it.
 
Guess it's time for a JY run, see if I can snag an ABS module (and hope it's been fixed) and a stalk. Jumping the pump at the socket proved the wiring to the pump is good. Creating the button and LED setup will be a last resort.
 
And if the one you grab is bad, send it off to get repaired. It's a fairly straight forward fix, there are write ups floating out there.
 
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