Depends. If the mileage is too much out (like 20k) over the mileage stored in the EIS, the cluster may display dashes (-----) instead of mileage.
YMMV, obviously. Some people were able to put a used EIS with different mileage but kept the cluster mileage, others had to replace both as a set.
Hi again, so here's what I've done so far. I tried to find a matching TRP set but had no luck in doing so economically for my C32. What I ended up doing was buying an entire donor car. Now I thought this would make things simple but nope.
Here are the facts:
My car is a 2002 C32 AMG (the one I am repairing) I think built in 2001. It has a key that looks pretty nice and modern, chrome sides, separated buttons on the face, OEM key, backup metal key matches all the door and trunk locks. To my knowledge, everything inside the car electronics wise is original. How/why one of the previous owners got the modern key (I suppose maybe after losing their key?) is unknown to me. The car of course when it was built had to have had the normal older style key. My car by the way ran and drove flawlessly before the incident.
My donor car is a 2003 C32 AMG (bought it minus engine and trans and some things that were parted out) I think built in 2003. It has the older style black key, same type as one of my 2005 W211s (my other 2005 W211 has a chrome key slightly different from my C32's, all these different style keys make no sense to me). It ran before it was parted out, metal key matches all door and trunk locks. To my knowledge, everything inside this car is also original.
So, I pulled the ECU, Front SAM, Cluster, EIS, and ESL from my donor car expecting it to all pop right into my C32. Nope, literally everything is different inside??? ECU harness same, all plugs on front SAM are same, cluster plug is same. BUT, my original EIS had four small plugs, donor one only has three (one large flanked by two small). Original ESL had a three pin connector, donor one had a larger connector. None of the wire colors matched up at all. Steering column also had different wiring and plugs. Prior to disassembly of the cars everything had looked identical inside apart from a few different options. I am ridiculously confused why everything would be different, and have invested so much money into this project at this point. I refuse to give up.
So I went back to my donor car and dismantled it further. Took the dash harness out, and took the loom and wire wrap all off. Traced every wire related to the ESL and EIS and completely separated this from the rest of the harness to keep it all self contained. Ended up with a harness that had two connectors that go to Front SAM, one connector to light switch (idk why so much of the ignition related wiring is tied into the light switch), the connectors that go to ESL and EIS, one pair of green/white wires, two pairs of brown/red wires, one red/blue wire to instrument cluster connector, one blue/grey wire, one fuse holder, and a small bundle of grounds.
I detached the respective connectors from my C32, connected the two front sam connectors to front sam (one connector needed depinning and insertion of cigarette lighter wires and a pair of black/brown wires), plugged light switch into my new light switch connector, connected up my EIS and ESL, plugged green/white twisted pair into it's junction box, plugged the two pairs of brown red wires into their junction box, depinned and inserted red/blue wire into cluster connector, tapped blue/grey wire into matching bundle of blue/grey wires, installed fuse holder and fuse, and installed the ground at grounding post. I popped in my original 168k mile cluster.
Gave everything power, electronics all came on. Cluster showed SRS error which it didnt before and teleaid due to taking off center console. Mileage flashed between dashed lines and 168k, showed correct outside temperature, *fuel level showed correct fuel level 1/4 tank* *Using black donor car key, car unlocked and locked*. Put black key in EIS, ESL unlocked. Car did not start. Windows don't work, seats don't move, steering wheel buttons do nothing to cluster display. It's as if the car doesn't know it's in run mode?? Like as if accessory power doesn't even come on.
Tried installing 190k mile donor car cluster in, still no start, showed correct outside temperature, *fuel level no longer shows anything*, mileage stops flashing dashed lines stays at 190k miles. Frustrated, reverted everything I did back to original wiring (kept it all intact) including front sam, etc, put back old eis and esl. Chrome key no longer unlocks or locks car, can't remember if it did before I did all the wiring stuff. Left the donor car ECU and SAM since mine are toast (did at one point put back my original front SAM just to see what would happen, no difference at all bad or good) Still no start ofc, but it acts just like it does with the new wiring and new EIS, ESL, key. As if it makes no difference that I put all that in.
Connected up all my new stuff back in again being sure to disconnect old things (except left green pairs and brown pairs as I can't trace them without dismantling my dash, BUT I did just try to remove all brown pairs and green pairs from junction box just because, and attempted start, no difference at all??? Even though it's CAN wires so it should have made a difference, but nada, no good or bad difference), now black key does not lock/unlock the car anymore, outside temp on cluster shows 185 degrees instead of correct temp, mileage of 190k not steady anymore flashes now like 160k cluster did with dashed lines. Attempting to start does nothing. Again, as if it doesn't even know its in run mode? As if its only in key position 1 not start. With shifter lock cable hooked up to (either old or new) EIS, key in position 2, foot on brake, shifter does not unlock, have to use the emergency release. Steering buttons still don't work. Currently at a loss for what to even try next.
I'm just mad as to why the hell the EIS and ESL connectors are different in the first place, and no one online seems to have a single clue as to why. On eBay I see some sellers advertising EIS's for 2003+ W203 that match my donor car's connectors so at least they seem to know there's a difference but I see no other mention at all anywhere online that the dash harness for an early w203 is completely different to a later w203 (despite both being prefacelift) or why this is the case. I also can't even find any EIS like mine with four connectors and a chrome modern key (my 2002 C32 key looks exactly like a 2015 CLA key if you want to look it up, 2003 C32 key looks like every other early W203 black key).
If you were in my situation what would you do? My current thoughts floating around in my head are that I should find a junkyard W203 that has the same exact dash harness as my donor W203, grab the harness and related steering column electronics and such from that, and gut my C32 and throw that harness in there. I am wondering if somehow my original *and* my donor front SAM's are toast or got ruined in this process somewhere hence 185 degrees and no locks etc. So I'll grab one of those too to see what happens (want car to start first, option coding can come later) Then, take my donor C32 modules and plug *everything* in from there to my C32 with that nice fresh harness. This seems like a last resort solution though (assuming it even works
) and I would be open to suggestions for easier things to try first. I wish I had STAR Diagnostics, don't know for sure but I feel like it'd help point me somewhere. I still need to change my engine harness after all this (mine is technically intact but burnt wire insulation and such in small places, need car to at least try to start before I go there though, I have all wires isolated and insulated well so nothing shorts there), at least that should be the same between the cars.
I know I wrote a lot but I tried to be as descriptive as possible, read through it, you at least might find some entertainment value, but any suggestions would be extremely helpful!