Project CRD MJ:

[Sir Sam]

Got the fuse box in place today and started laying out the interior harness's, The dash harness's and engine bay are easy enough to deal with since they pretty much sit in the same place for the MJ as the XJ. However the body harness is a little different, today I placed it in the cab as is and didn't like how it was working out since the harness was meant to work with the 4 door XJ.

I stripped out the rear door wiring for the courtesy light and power windows, as well as the rear overhead light wiring. I still need to pull out the speaker wiring, rear wiper, and defrost wiring. I also then need to figure out how to arrange the remainder of the rear light wiring. the plugs used at the back of the XJ behind the spare tire will reach part way, but are not weatherproof connectors so they really shouldn't be used under the bed as-is.

I stripped the harness wrap bare so I could move some things around, but I am attempting to avoid a million splices in the harness.

[Sir Sam]

Short video showing the interior harness work:


https://www.youtube.com/watch?v=L1IF-AF5pLQ

[Sir Sam]

Longer video showing the engine bay harness work that needs to occur:

https://www.youtube.com/watch?v=RX91ttWpfXQ

[Blue XJ]

Originally Posted by Sir Sam

I also then need to figure out how to arrange the remainder of the rear light wiring. the plugs used at the back of the XJ behind the spare tire will reach part way, but are not weatherproof connectors so they really shouldn't be used under the bed as-is.

[/IMG]

If I'm not mistaken, when I used the XJ harness on my MJ, I had to make a new rear light harness. The MJ uses the same bulb for tail/turn, where as the XJ has separate bulbs. The harnesses won't just connect and work properly.

[xj_man_646]

I'm glad to be seeing progress on this once again

[Sir Sam]

Originally Posted by Blue XJ

If I'm not mistaken, when I used the XJ harness on my MJ, I had to make a new rear light harness. The MJ uses the same bulb for tail/turn, where as the XJ has separate bulbs. The harnesses won't just connect and work properly.

Yup. The MJ light behavior is more like trailer lights are. I'm debating how I want to rewire and convert. I might change the light setup to match the XJs more closely. I have a few thoughts I need to flesh out.

[Sir Sam]

Tested the TJ gauge cluster finally!
https://www.youtube.com/watch?v=xpO4isRTThs

However I thought the KJ plugs were the style I needed but it turned out they have more pins than the TJ, so I need to find the same connector type but with fewer pins to fit the TJ cluster.

Grrr, back to the junkyards to raid 15 year old Chryslers.

[Sir Sam]

I will need to do some more testing in the future where I read through the OBDII port with a scanner to show what PSI to oil pressure sensor is seeing, and how that translates to the position on the TJ guage cluster. The TJ cluster is reading oil pressure through the PCI bus from the ECU, and then displaying that as an analog value. The question comes up as the the calibration, when it read "half" what PSI was that? When it went higher to 3/4 what PSI was that?

If you noticed the oil pressure gauge is the only one that does not have any units shown. This is because on the 2002+ TJ the oil pressure gauge is basically just an idiot light! The sensor on the newer TJ is a discrete, meaning it is either open or closed. In theory, when off or no pressure the switch is open circuit, and then when the engine is on and oil pressure is "good" it is closed. This way if your oil pressure drops below "good" or if it fails it should go open circuit. What the TJ ECU does is read this open or closed switch and send a value to the cluster. So the TJ cluster reading from the ECU only sees 0 PSI/bad, or X PSI/good. This means that on a stock TJ the oil pressure gauge either shows zero, or middle. Since the gauge is then basically just an idiot light they removed the units of measure.

However since the CRD ECU does read an analog pressure from the oil pressure sender the REAL psi is transmitted over the PCI bus, and since the TJ cluster is reading a real analog value it drives the gauge accordingly. The only thing left for me is to determine exactly what pressure the middle means, and exactly what pressure the high means.

I am working on a way to read the calibration from the processor onboard, which may allow me to change the scaling factor on the gauge. Likely that will be much further along, I'm just happy the Main functions, fuel level, coolant temp, RPM, and presumably speed all read correct.

In final form this will be wired into the normal dash wiring for the cluster for all functions such as turn signals, lights, 4wd indicator, etc, leaving the obdii port completely open like factory.

[Blue XJ]

Originally Posted by Sir Sam

Yup. The MJ light behavior is more like trailer lights are. I'm debating how I want to rewire and convert. I might change the light setup to match the XJs more closely. I have a few thoughts I need to flesh out.

I believe I just separated them in the MJ tail light, had one bulb for stop and one bulb for turn. It was the easiest way to go at the time.

[Sir Sam]

Originally Posted by Blue XJ

I believe I just separated them in the MJ tail light, had one bulb for stop and one bulb for turn. It was the easiest way to go at the time.

Ya I'm looking to get 2 dual filament LED bulbs use the dimmer filament for parking lights, the upper brighter for brake, and the lower brighter for turns.

I'll end up running one of those LED strips below the tailgate to give me some extra lights as well.

Thats about the best plan I can come up with right now.

[Sir Sam]

My coworker came over last sunday to use my pressure washer on his newly acquired wildernest to get it cleaned up, I decided it was a good time to open mine and take a look inside the back of the MJ........I'm find all sorts of parts I forgot where back there.







Fun times ahead! Looking forward to having both MJs out and be camping!

[Sir Sam]

I made some progress on the TJ gauge cluster, I cannot seem to program less than 1000 miles, I suppose thats close enough to zero? I was just really looking forward to seeing it run up from zero. I might keep playing with it, I also want to figure out to reprogram the VIN.

[6DoF]

are you able to manipulate each digit ... but not all of them to zero at the same time?

[Blue XJ]

Originally Posted by Sir Sam

Ya I'm looking to get 2 dual filament LED bulbs use the dimmer filament for parking lights, the upper brighter for brake, and the lower brighter for turns.

I'll end up running one of those LED strips below the tailgate to give me some extra lights as well.

Thats about the best plan I can come up with right now.

That's how mine was, although I never got the LED strip mounted.

[Sir Sam]

Originally Posted by 6DoF

are you able to manipulate each digit ... but not all of them to zero at the same time?

If I try to program 1-3 digits its like it overflows and sets the mileage to like 1.8 million miles.

So 999 seems to have an issue, but 1000 seems ok. I also cannot enter 000001, I can only enter 1.

This is being done with a chinese tool that supports many different vehicles. The tool is reading the BDM port of the HC912 motorola/freescale/nxp cpu. In theory I should be able to write anything including new program code through the BDM port.

More research is required. I soldered some pins into my gauge cluster for development purposes so I can keep playing. I really just want to figure how to zero the cluster and change the VIN. I'm working to re architect the electrical system in the CRD MJ - I want it to be like factory, and part of that is having the VINs correctly programmed.

If I can get the BDM port to read via terminal on a PC then I think I should be able to find the mileage and VIN in HEX and write those values back via the BDM port.

Originally Posted by Blue XJ

That's how mine was, although I never got the LED strip mounted.

LOL ya, I know how those things go. I really want as much visibilty on the rear - I'm putting lots of effort into this thing and I don't want some jackass to rear end me because the factory lighting kinda sucks.

[Blue XJ]

It sure does, I was told a few times by buddies behind me on the trail that they could barely see my brakelights. I wish someone made replacement tail light boxes like they do for XJ's, I would have swapped them out back then.

[6DoF]

can you make the odometer say BOOBS on start-up??

[Cobound]

[awheelterd]

I haven't read everything but why bother with the tj cluster?

[Sir Sam]

Originally Posted by awheelterd

I haven't read everything but why bother with the tj cluster?

Newer TJ cluster uses PCI bus instead of CCD bus which is what the CRD ECU uses.

If I want any gauges to work I need one that reads data on the PCI bus.