JEEP XJ Cherokee Speedo cluster hack.    

How to get use a used junk yard (wreckers) cluster in your  Jeep,  (DIY)

The FSM is here.

Click instrument chapter.
Now go to page in that chapter, there.
The cluster is an  all electronic display with a brain (plus some side wiring to some lamps) Jeep wants $660 to $1024 to buy one and dang $500 core charge,  not cheap ever! Not to  mention the $100 /hr to put it  in...
and uses a CCD bus to communicate to the PCM   Cluster brain.
It's just a stand alone digital display, the gauges are analog but ditital driven. The Odometer is 100% digitial.  (and is a problem, due to Fed. regs.)
Page 2 of the FSM tells you just that.
When exchanged it  must be remarried to the system. (learned, or programmed,)
Fed laws here, make this hard (odometer rules) (and like all fed laws, gets worse year by year.....)
What happens in REAL time, is the PCM asks the cluster it's VIN and fails. (you bought a used cluster i'm sure now its dead, this is all EXPECTED)

Some lamps are still hard wired, your not having that super easy problem, but the FSM covers that 100 % RTM.

Did you do the self test first? That is first, to see if the used head is any good, or just needs some new lamps... sure.

If you do that, it tests the whole cluster 99.0% (can't test the CCD bus (comms this way)
All by its self.
"actuator test" is official name of the ACTION taken, in the FSM book.
Seen here , video  of self test.

If you scan the PCM (did you) and the comms fail, that could be the reason the origional display cluster does not work. Not scanning is silly.  Scan first, ask questions 2nd! and win.
Next, are comm fails, ill quote this. Cluster installed, key on, scan too shows comm errors.  oops.

"if the instrument cluster detects
a loss of CCD data bus communication, the cluster
will automatically turn the MIL on and display the
message “NO BUS” in the odometer" (has smarter VFD display)

If this happens cluster or many  things die.
other  symptoms...
The odometer will freeze at last known odometer readings. if comms die, (assumes VINs match) 
on most jeeps like this, the PCM and Cluster must be remarried, (or it fails , a dealer fix) but wait....
Here is very good youtube of smart hacker
programming the XJ cluster to work.

(odometer sync) hackers, love this guy,  (my guess $100 in parts saves you $1000 at dealer)

As you can see, the VIN is in Clear text (called ASCII) and starts at hex offset,  35h.   the 4A(hex) is ASCII for J, and J is the JEEP VIN code for JEEP company. (VIN rules USA) and we all know that is 17. digits .ending in 36 above. change all 17. to yours.
(takes reprogramming (flashing the serial EEPROM "FLash chip" in the cluster.

that vedeo shows  an  industry standard flash programmer. It does 1000s of EPROM , or EEPROMS (flash).
With its 40 pin DIP ZIF socket "in blue-green", that adaptor to this ZIF (zero insertion force)s socket 
from DIP to surface mounted device (Flash)  it is... in the cluster. "his is made by Fairchild" (one of the first makers of integrated circuits and the spring board to Intel)
a special cable is needed. the cable is sold in all stores that sell these programmers. it's a known cable setup.
This is hacking steps, the  display has now power applied,, do not power it up now.
He reads the EEPROM first.
Then patches that read code, and  , and then reprograms the cluster flash chip.,with a new vin.  (if you know your legit Miles, do that next , or just hope the PCM corrects it , later)

He first patches the VIN, (this man be the only step you need to do)
See now?, why the used cluster youg found, now fails in your car?
You got one with the wrong vin... (which is always the case)
Look first at your cars body vin, then look here. see, it's wrong.!

Secret 1 , hex address 35 +
He  is a supreme pro here ,  he backed up first. (a win) (read code, then save code, then hack and burn)
The data:  of ,  00d5's are mileage terminators, don't touch those!

That bench test could have included the self test.  by holding reset odom,and turning on IG power pin , on the bench.

The main ECU or in newer cars BCM too will not like illegal clusters. (double trouble)
The vin must match or fails.
Now you have the fULL story.
Do not use lower miles, that is illegal in the USA...for sure. do not do that. (it's not right either)  I'm not advocating that. ever.
Please, , this is just to cheat stealerships  , and to  be GREEN and recycle perfectly good  used parts...  amazing......
I also bet the dealer will not use, used heads, if you supplied it, (but do ask)

On newer CARS (JEEPS) the PCM may look at miles stored in PCM and BCM and in cluster too and if not 3 way matched, fails. (and for sure VIN mismatch)
(but not XJ just VIN  fails) that dirty trick (x3) is on new cars. (and nicely very un hackable, for JEEP)

My crude journal, nothing fancy , sorry...  with lazy caps key,  my bad..... but lazy I am, retired puke and all.

PS (theories)
Found out the dealer can not reprogramm your used cluster. There scan tool limits this.... (they can change miles in PCM ,after all they change them all the time)
I suspect the cluster blockage, is so dealers can NOT roll back both. (big time illegal that)
But now you can write down your old mileage and make them match. (it may have to be pretty close i'm told)
But how does the dealer install his new $1000 cluster?, my guess is the mileage is blank.  (or some other secret rules, like blank vin?) < but I don't care, I'm never going to buy a new one.
Be nice hacking test there, blank miles, blank the Vin see if head now wakes up and copies all that to the new head.
or blank only the VIN. see what happens.
ok , I found the base forum for this...

rev 1   ++++ 10-20-2015