ACE1252

I find it hard to believe that 3 modules would be bad too.....very unlikely. Impossible? No, but certainly unlikely.

Are you feeding the VSS signal, from the sensor, to the PCM, then using the LT1 PCM "converted" VSS signal to the cruise module? Next using the LT1 PCM "converted" VSS signal drive a "Dakota" box to speedometer?

Kinda a long shot here, but are you sure you have a manual LT1 PCM program? Is it possible that it's an automatic program and looking for other inputs or outputs from an automatic tranny in order to enable the cruise to the module?

I'm on call for work this weekend and am not going to be able to look over the signals on mine today, but will attempt to do so in a couple of weeks.

tylerwerrin

I suppose it's possible the tune I downloaded wasn't a native T56 tune. I scanned it with Tuner Cats, and everything looked like a confirmed T56 manual tune. Do you have a confirmed tune that I could load?

As for the VSS, the feed I am using which is feeding the cruise module is coming straight from the PCM -- the dakota box is downline, in the cab. I'm going to try running a new wire straight from the B8 terminal to see if that changes anything. Finally, I'll try a spare PCM that I have to see if that does anything.

Thanks for the continued help!

ACE1252

You have no SES light correct? Just thinking about it some more, if it was an auto tune on a manual, I think it would have thrown some auto SES codes without the auto tranny connected.

tylerwerrin

nope, no SES codes at all. I did download the tune from the internet, from the Monodax forums so I don't know for *certain* that it was a native M6 tune, but everything seems to be OK otherwise...

tylerwerrin

Hi guys,

I don't know if anyone would know this, but is there a way to test the motor for functionality, with the unit out of the car?

ACE1252

The manual states that the module is not serviceable. I would guess that the motor is some type of stepper motor....but without looking at one I'm not certain.

Do you know anyone with an LT1 Z28? Would they put one of your modules in their car to test it? Might be a good way to verify one of them.

Any chance one of the enable signals is toggling on and off while driving? Do you have a way to monitor the signals on each terminal while the car is moving at speed? That might be the next step in the process.

tylerwerrin

I posted a few pictures a couple posts ago -- you can see what it looks like inside. It's definitely a little stepper motor inside.

HOWEVER... UPDATE

I swapped the motor this afternoon and drove the car around the block. I got up to around 30mph, and pressed the button, and nothing happened. Disheartened I tapped the SET switch a few times in a row and much to my surprise, the car surged forward a bit and seemed to hold its MPH! The blocks here are short though, and I had to brake almost immediately.

I wasn't sure if it was just the car decelerating and the clutch engaging & disengaging the pressure plate. I tried a single press again, and no luck. However, with a few taps, it seems as though the system activated for a second. Unfortunately traffic was horrible this afternoon and I wasn't able to get above 30 to test it again. I'll try again tomorrow and see what happens. I don't want to get my hopes up because even if the cruise is "sorta" working, it's not completely functional the way the manual describes.

The multiple tap thing is interesting because if anything, the car surged -- however the manual states that by tapping the set switch, the car should DECELERATE. Pressing the master set switch increases the MPH. Interesting.

I'll see what happens once I have some open road in front of me!

tylerwerrin

Hooray! The cruise is working perfectly -- looks like the problem was the cruise stepper motor was shot in the original unit I was testing with. Both modules were OK. It's always the last place you look, right?

Thank you Ace & Bob for sticking with me for the past couple weeks. It's great driving the car with cruise, not that I'll get to really enjoy it while driving around LA itself :-p

All of the functions described in the shop manual are working -- tap up, tap down, brake disengage and cruise memory. I still need to add a clutch anticipate release switch in paralell with the NC brake switch for added safety, but for now the car is driveable. I'll root through my box o' stuff and see if I still have a switch lying around that could do the deed. At the very least I have some microswitches that I used when I built an arcade cabinet a while ago that I think could work nicely, if I could mount them on the pedal.

So for anyone in the future if you are planning on wiring cruise control to an XJS or XJ6, the schematics work! Use them with confidence!

ACE1252

That is great news!

So were you just swapping the boards and not the entire module(motor and all)? I was under the assumption that you were doing the entire module(aren't the motor and controller board in the same unit??). That would certainly explain why you went through so many with no change. Well done on finding the problem.