"cat-code plug conundrum revisited" or "between a rock and a hard place"

Sergeant Pluck

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Apr 28, 2003
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The corner of Miles and Gil
"cat-code plug conundrum revisited" or "between a rock and a hard place"

ok, so i'm on GS number 2, and i've just dumped the cat and fitted my y-piece again, removed the cat-code plug and grinned manically at the all round improvement in power, smoothosity, noise, etc., whilst remaining secretly paranoid about the fueling issue. so i pose the following question; (heard this one before?!)

i've researched this issue extensively on this site and elsewhere and here's what i've come up with so far.

the name 'cat-code plug' is a bit of a misnomer, as the CCP doesn't just alter a *standard* fueling system in a way that accomodates a catalytic converter, it actually chooses one of six different fuel-maps built into the ECU, depandant on the BM bike model and it's set-up. the plug itself (yellow, or sometimes pink on a GS - both of mine have been yellow) contains nothing more than a jumper, rather than any specific electronic wizardry. the fuel-map chosen by the CCP when installed is one which causes the carburation to run very lean because a catalytic converter needs to get *very* hot before it begins to convert effectively.

hence, when you remove the catalytic converter from your (my!) bike and replace it with a y-piece without removing the CCP, the bike will breathe better, run even leaner, getting even hotter and consequently putting your valves in danger of burn-out. this is the *rock*.

so to combat this, you remove the CCP and reset the motronic, but;

when you do this, you are setting the ECU to a bog-standard, lowest-common-denominator, get-you-home-type fuel-map (i understand this as similar to running your PC in 'safe-mode'), which runs much richer, using more fuel but not endangering your valves. so it's safe, but not 'honed' - not the correct or 'perfect' solution - and therefore the 'hard-place*. you with me? ;-)

so naturally my question is; firstly am i correct in the above assumptions? and secondly and more interestingly, is it possible to obtain a CCP who's jumpers are set to choose a fuel-map specific or better suited to a GS *without* a catalytic converter? or failing that, does anyone know what the correct jumper configuration of such a plug would be so that i could make one up? this is the *between*!! :clap

yours in eager anticipation,

Re: "cat-code plug conundrum revisited" or "between a rock and a hard place"

pr0ne said:
or failing that, does anyone know what the correct jumper configuration of such a plug would be so that i could make one up? this is the *between*!! :clap

yours in eager anticipation,


That is the million-dollar question!!! All the fuel maps / jumper settings that I've been able to find relate the earlier Motronic on 1100's, not the 1150's. Any experts out there like to comment?? Are you there, Panzer???
Mr Prone, on a related subject... you mention 6 different programmes the ecu can choose from. Sometimes when I am riding, the characteristics of the engine seem different to the previous ride. For example, sometimes it vibrates badly from 4000rpm and other times it is remarkably smooth. Is there any way I can identify which prog it has selected and fix it on the one I like rather than let the bike choose.
Den - god knows!

I think that your bike will use one of it's six fuel-maps, determined by which plug is installed, and thats the one it'll always use until you physically change it (maybe with a powerchip, different cat code plug or something). The actual second-by-second fueling is then controlled by the motronic referring to this map to choose the mixture based on engine speed and feeback from the Lamda Sensor.

This is why people might want to install a powerchip, as this has many more maps available and you can choose which one you want manually.

i could well be wrong (and hopefully if i am someone will put me right!) but this is the conclusion i've can to after (too) much research!

pr0ne said:

This is why people might want to install a powerchip, as this has many more maps available and you can choose which one you want manually.

Thats the conclusion I came to.

I don't claim to be an expert and I guess I have read the same stuff you all have here, at advrider and elsewhere.
Better safe than sorry is my guide on this one.
Plus I got a good deal on a second hand chip off Metal Man ;)
Currently running Remus Revolution (baffle out), Remus Y and BBPowerchip stage 3 - very happy with it.
Somewhere Iv'e seen a drawing listing all the different maps, you are right its just a jumper wire.
I am sure that someone here (maybe Mechanic or Proboxer??) said that the cat code plug was designed for the 1100, and is not needed on the 1150.

I could be wrong, itwas some time ago.

In NA we refer to the CCP as The Little Yellow Bastard (LYB), Little Pink Bastard (LPB) - you get the idea.

My conclusions after much hair-pulling and research so far:

0. "Surging" is actually a misnomer. It's hesitation due to a fueling change.

The CPU is programmed to take info from all sensors when on a moving throttle. However, when on a steady throttle, or cruising, to lower emissions (my guess is surging is at RPM where EPA or national equivalent checks for emissions), CPU ignores all but O2 sensor and shortens open time for injectors to squirt fuel if O2 says mixture too rich for tree-huggers. This is why bike "hesitates".

1. The LXB is a simple jumper designed to look like a relay. There is NO way to program anything other than the 6 (including base which has no jumper installed).

No jumper is NOT limp-home mode. Limp home on Ducs, etc limit RPM and the bike barely runs.

Each program reflects where bike is shipped (altitude above sea level, emisisons testing requirements). Some bikes have none due to dealer pre-sale inspection oversight.

Many test-ride bikes are missing LXB. Bikes have also gone to dealer without one only to be returned with one.

2.Dealers look at you with empty eyes when you ask questions because most have no @#$% idea - they just want to sell bikes. I've never heard of anyone getting shite from a mechanic for not having one in bike.

3. Don't know why (lots of headscratching across the pond on this), but OEM multi-electrode sparkplugs are a BIG contributor to surge and rough idle and are an easy fix.
Steps I've taken and results:

Bike: 4000 km '03 single-spark GS dealer demo.

Symptoms: Bad surging at usual RPM (oddly missing before pre-delivery "inspection"), etc.

Rough idle, even for a big twin. Started only after 3-4 tries with key. Warm up was touch and go for first, say, 30 seconds.

A) Did careful TBSynch. Ran a little better but surging still there, but maybe a little better using seat-o-pants indicator.

B) Raised idle some 100-200 RPM. Bike idled better, but still rough with a little quicker snap off stop lights.

C) Pulled LYB and reset CPU. Surging almost gone, idle better yet, bike ran very well, lower vibration, but still took 3-4 cranks to start.

D) Tossed OEM plugs and replaced with Champion RC9YC (1 UK Pound / Pair) gapped at 1.00mm.

Sweet Jesus on a Raft, what a difference!

OEM plugs looked a little dark, but the Champions transformed the bike. This is something a number of ADV Rider members have reported as well after months of chasing expensive solutions to surging.

Bike starts on crank 1 or 2. Idles like a different bike and NO surging at all.

I don't kow if the plugs would work as well without the other steps or not. But for the little time and the C$2.99 spent, the bike was just transformed.

My wife's new dual-spark has no surging but is a bear to start. Will be converting hers to Champions ASAP.



Canuck GSpoter/Reformed DucFlogger (ADV Rider)

Ride safe.
Good and bad news on the cat plug thing. Last month I met a 1150 RT rider who had threatened to return his latest bike to the dealer because he was so fed up with the way it surged in town.

This bloke has got 40-odd years riding behind him and has had BMWs for donkey's years, so he knows his stuff.

Anyway, the dealer replaced his three-prong cat-code plug with a two-prong one. Apparently the original one cuts the fuel supply to the injectors off completelywhen you shut the throttle, so when you open up again slightly there's a hestitation and jerkiness from the engine. It was done this way to comply with US emission laws.

The two-prong one, which is an official BMW part, lets a trickle of fuel through, in much the same way as ordinary carbs would and it made a world of difference to this bloke's bike.

The bad news? He let me try the two-pronger on my GS, which normally runs with no plug in. It rode more smoothly while the engine was cold, but once it warmed up the plug made no difference at all. Bugger!

I've read all of the above and am still no wiser - I would really appreciate some advice.

My GS is a 2001 model and the engine performance is great, no surging, stalling or bad flatspot. I've only had it a few weeks and have no experience of BMW's.

However I have removed the cat and am just about to fit a Remus race can and before reading the above believed that the sensors would adjust the fuelling to suit (yeh I know - optimistic!!).

So what should I do?
Remove the cat plug.
Change it for a different one (if so which and from where).
Leave well alone (worried about burning valves now!!)

Thanks for any advice.
oopps - forgot to say that although everything seems great with the performance it does somtimes backfire on the overun - not often and I believe it happens on a just closing throttle.

Is this usual or is it connected to cat plug dilemma???
I checked the socket on mine and its a UK bike and only pins 30,87,87A & 86 are wired, the yellow CCP is connecting pins 30 & 87, also I have located an article by Rob Lentini on the subject, now bear in mind his is a US version and has different pins wired, I attach the doc.

Maybe The Mechanic can shed some light on the issue.


  • cat code plugs.doc
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hi gavin4333,

my personal advice would be to remove the CCP with your new system for the time being. it will mean you are running richer (and using more fuel) but you won't be burning your valves out (this will happen if you run too lean ie. hot). the "changing it for a different one" option is exactly what i'm trying to find out about. from what i gather there are only 2 CCP's available for the GS (yellow and pink), and we don't know whether either of these choose the most suitable map for your particular set-up. (we think they choose a map that is very moody on the fuel front - delivering a lean mixture in order to heat up the cat and reduce emissions).

hello Canuck GSpoter

i agree with much of what you say there, however - i'd still really like to know more about these 6 maps. you mention that the map chosen when no CCP is in place is NOT a get-you-home type map, which i like the sound of, but i reckon we still need more specific information on these bloody maps! somebody must know! any BM techs on the board? any way to infiltrate BM's holy edifice to get this information now that a new, better model is in production?!

hey jimb!

i think i read that document in the oilhead maintenance PDF (is it the same one?). if i remember correctly he's talking about the older motronic and the not (2.4?) version fitted to 1150's, which may or may not have the same maps. so confusing and still none the wiser!!

cheers all and i'll keep searching!

pr0ne said:
i think i read that document in the oilhead maintenance PDF (is it the same one?). if i remember correctly he's talking about the older motronic and the not (2.4?) version fitted to 1150's, which may or may not have the same maps. so confusing and still none the wiser!!

Correct - that is the one I saw. Lentini did some (inconclusive) experimentation with jumpers to activate the different maps. No-one seems to know for certain which is which. Mine runs without CCP, and with Techlusion on factory settings and goes like hell. Got a Y-piece + Remus revolution minus baffle. Plugs are a nice light brown / tan after a full-throttle run. Dyno run imminent, I think, to see if any more torque can be liberated.
good work, littlered!

i'm going to get mine dyno'd as it is now (standard can, y-piece, no CCP) and then do it again when i've bought a techlusion and see what the differences are....

Thanks for the advice, now running without CCP and everything seems ok, will do a flat out plug chop this weekend to check plugs.

One last question (I doubt that!!!), what is a Techlusion? Some sort of tunining aid?

For what it is worth.....

Just spoke to a BMW main dealer (like I said, for what it is worth) 'cause you guys have panicked me.

They said that removing the cat on an 1100 required either the removal of the cat code plug, or preferably replacing it with a different one.

For the 1150 they said that they leave the yellow one in place, but you could equally remove it - as far as they were concerned it made little to no difference. This is apparently because the lambda probe overides everything on the 1150.

Like I say, for what it is worth

(I'm running Y piece, Revolution (baffle in), K&N, Yellow Cat Code, and the bike seems to run fine, and is using almost exactly the same amount of fuel it did in standard trim)

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