I apologize for starting another P1688 thread, but I’m getting desperate. I have the standard issue – hard acceleration to about 5,500 RPM and surprise – engine shuts down to limp mode. Restarts after a stop and ignition off/on. Per my code checker I get a P1688 and P1688 P. It’s a 2003 MCS with 80,000 miles.

First time this happened (last week) I replaced the crank pulley, thanks to other threads on this site. However, that’s obviously not my problem. The car has been bogging down going up hills with the AC on, but that’s remedied by shutting off the AC.

I followed Detroit Tuned Bypass Valve Installation Instructions (https://store-zhkcqkob.mybigcommerce...t/DTBPVINS.pdf) to examine the valve and throttle body, but I was unable to remove the hose clip (step 8) and remove the valve.

As a result of my failure I took the car to an independent Mini garage. They re-synced the throttle body, cleared the codes and everything appeared fine. 3 days later, I’m back at the beginning. This time I noticed a slight burning smell in the area of the bypass value and throttle body.

I've finally got that hose clip off, but now I can’t get the “bullhorn” off that hose (step 5), nor can I get the hose off the throttle body (step 6).

Can anybody out there help me?

 

OK, a night's sleep, renewed vigor and I got the Throttle Body off. It was dirty, but no where close to the intake manifold. I cleaned the TB with TB cleaner and tried to clean the manifold, but couldn't get too far into it.

I tried to test the TB via some instructions I found on a thread. "Measure between pins 2 and 6 and get around 1000 ohms. This is two 2000 ohm resistors in parallel.

Measure resistance between pins 4 and 6. I got about 1300 ohms. Very slowly push the butterfly open and watch the resistance change down to about 450 ohms at wide open. Let it close. Change leads to measure pins 4 to 2, mine read 620 ohms. Slowly push butterfly open and watch reading increase to 1300 ohms, at wide open. If you get readings like this then the potentiometer at pin 2 is good.

Repeat the above procedure for pins 1 and 2, then 1 and 6. The most important part is the resistance changes in small increments in response to small changes in butterfly movement! watch for large jumps, and it going open circuit."

I don't have a pin diagram so I didn't know what pin was what. The only pair I could get a resistance on did not change when the butterfly was opened. If I can't get a pin diagram, I will attempt to get my independent Mini shop to test tomorrow.

 

DUH!!! They are inside the plug. Tested resistance and I got 866 on 1 & 2, and the others didn't increase/decrease smoothly. Actually on 1 & 6 it increased to over 1300 then dropped to 1200 at wide open. I ordered a new TB.

 

also, check your supercharger pulley for proper fitment. we've seen where a supercharger pulley loosened its way up over the course of 3-4 years then started spinning on the shaft of the supercharger. also, how did you tighten your crank pulley bolt? high-powered impact gun? we've also seen crank pulleys slip on the crankshaft when not properly torqued/tightened. good luck.

 

Crank pulley was tighten with a torque wrench, car in gear with screw driver in brake rotor to prevent rotation. TB replacement still failed test - 1st gear to 5,500 RPM, 2nd gear to 5,500 RPM, coast to 3,500 RPM, full throttle back to 5,500. Did this 4 times and still popped to limp mode on 4th time. Replaced by-pass valve and all seems to be fine - so far.

 

Hey JT911, are you still having the same issue, or did the BPV solve this problem?

I have an 02, which has the same exact symptoms (not sure about the codes, haven't read them). I pulled the entire intake system off and cleaned it. I checked the butterfly on the Bypass and the TB. I actually put the bypass valve up to the light to see if i could see any peaking past the butterfly. I adjusted the screw on the BPV to ensure it was closing all the way, and put it all back together. Car ran great for a day, but then it sent me back to square one. It will reset upon start up, and if i don't hit the gas hard (rev past 3,000-3,500 rpm) it will run fine. After hearing that this engines behavior can be caused by both BPV and Crank pulley going bad (not usually at the same time obviously) i ordered the following:

New Gates Racing Drive Beltl, 0% Alta Crankshaft Pulley, and a Detroit Tuned Bypass Valve. I went ahead and picked up a belt tensioner tool on e-bay for around $55 to make my future drive belt replacements easier.

I will try to add an update to this thread to provide closure to yourself and anyone else who might be up against similar repairs.

 

Ok, I wish I was coming back to you all with good news. Replaced belt, crank pulley, and bypass valve. Intake is clean, also cleaned maf sensor. Normal inputs: car drives fine, even when you press the gas pedal about half way and the car will rev out through first and second...and so on, BUT if you floor it, it will sputter through the rpms, and kick the car into the mis-firing 'limp mode' where the check engine light (CEL) blinks and illuminates solid, as well as illuminating the traction/stability control light. I've gone throughout the hoses, no leaks that I can see or hear. I am about at my wits end with this thing...any advice ANYONE, SOMEONE PLEASE give me some reasonable expiration for this. The only thing that I know I haven't had a chance to check/replace is the profile gasket at the intake and the supercharger.
If the engine can rev out under 1/2 +/- total throttle input, but struggles when WOT inputs are made, could this be injector related? I've replaced the plugs, but not the wires or coil pack...however in consideration of those, these symptoms don't make sense (to me at least).

I would be most appreciative of any feedback/direction.

 

Reviving thread from the dead. Did you ever figure out the problem?

 

My P1688 code turned out to be a bad T-MAP sensor in the intake manifold just above the radiator support

Bryan

 

Reviving this as Im having this code pop up,car go into limp mode then run terrible until restart. I have the exact same symptoms listed above but he never gave an answer as to the cause. I have a newish crank and belt and 2x checked the belt tension and all is good. Doesn't appear to be any vacuum leaks but I can try smoke testing it later.
damn p1688 code ! Ugh, my 1st problem a year into owning the car..not bad.

 

What car are you working on? Mine was a 2006 R52

T-map was my problem

Bryan

 

2004 mcs
it all started today after I strait wired my fan as it stopped workingworksheets low setting so I spent half the day figuring that out and for now I just strait wired it to run on high with a switch until I can afford a new cooling fan? Could this be related ???? I then test drove it after wiring up the fan and everything was fine for like 30min until I decided to run it hard to see if it would over heat or get hotter and it instantly went to limp mode and the code popped up then I spent the rest of day and night trying anything I could to hopefully fix it or diagnose it and 5 hours later , ive made no progress.
, I cleaned both map sensors , i had a tied shut bpv and I untied it with no change, I checked my belt and crank ect...car runs perfect until I get on it hard and once it gets to 5k rpm it turns into a slug and boost drops to 10 from 16 and if i don't immediately let off and try to drive through it it will go into limp mode and pop on the cel and eml and start to chug really bad until I shut it off and restart it.
I've tried clearing the codes , disconecting the battery for 2 hours while i cleaned the 2 map sensors one below the intercooler was pretty dirty. I can't imagine I suddenly have a boost leak..money is stupid tight right now so I don't wanna throw money at something its not..

 

FIIIIIIIIIIIXED !!!! omg what a pita diagnosing it. I even had to clean both map sensors 2x but the 2nd time I soaked the filaments in mafs cleaner for 10min and switched them around AND IT FIXED IT !
thanks NAM !

 

I dont think those 2 MAP sensors are interchangeable, someone here commented on that in a thread so I took a look on rock auto and there are 2 different part numbers from the same supplier for each location.

Maybe swap them back and see if the error returns.




Can a seasoned expert here chime in on the 2 sensors swapped being OK?

 

no, you cannot swap them ....there are two different part numbers, hence two different sensors....car will not run correct with sensors in the wrong position

Bryan

 

Yes, I found that out after lots of researching .
I guess the one in the intake manifold rite below the intercooler i think is technically a tmap sensor . They both measure the pressure but the one by the intercooler measures temperature also. Also the ebay ones DONOT work under anything more than stock boost i just found out. So if you need a budget tmap or map get them off rockauto , both my eBay ones were not suitable for my setup and both rockauto ones work perfectly . The ebay ones, once your car made over like 10 or more lb of boost ( was hard to accurately tell) they would throw it into limp mode..stupid things...
Also lol I'm an idiot , I did try switching around the sensors but somehow I reswitched them again and installed them correctly , lol derder

 

my car kept throwing the P0108 code as well last year....kept cutting off when I got on it....went right into limp mode...had to shut the car off and drive it home slowly. ...I tried the eBay sensors, couldn't find one that worked....I had one here that had a broken connector housing on it, so I put that one on and used a zip tie to keep it connected....car runs great now....

I need to find a good used or new sensor that works, just to have as a spare here...I have two Mini's that are supercharged

Bryan

 

I had the same issue, check the connector and push down the electrical pins in the connector a bit so that it makes better contact with the pins in the sensor. This solved my issue, found out after buying a new sensor off course...

 

I'm getting similar issues on my 06 r53 hesitant bogging when pressing the accelerator hard or over a certain rpm getting codes p1688 and p0107, I've replaced tmap sensor changed bypass valve for a good unit I believe it has a different type of bottom pulley but will have to check. Has anyone had this problem that wasn't t map or crank pulley ?

 

im right now with the same problem

 

Compressor Bypass Valve, check that as well. Does it run better if you ziptie it shut (only for testing).

 

Time to kick this old dog once again. P1688 is coming up but it is boggling my mind. I just recently purchased 05 R52 drove it 3 hours home and ran like a champ. It sat a couple days at home as I swapped out some seats and then I went to take my son to school and as soon as I pull out on to the road boom EML and service engine soon light and limp mode! I was less than a mile away from home so I "limped" home and then later around lunch went out to look at it just being curious I decided to try a quick drive to see if it was still having the issues after starting it and no EML light on. I proceeded to drive it around for the next hour or so with no issues at all ran great. Then later picked my son up from school and again no issues at all ran great! 2 hours later as i leave for work I get less than 300 yards from my house with almost no acceleration and boom EML and limp mode once again. Again I turned around and returned home to take a different car to work. Now after reading and searching I see the crank pully as being a big front runner however I cant feel good about that with the 2+ hours of good driving between the issue popping up again. So anyone have any suggestions as what to look at? _update_ so driving the other night and noticed the temp was starting to creep up a bit well long story short I got to my location raised the hood to let in a bit of air to cool things off and noticed a bit of smoke and strong burning rubber smell. figured i had a belt slipping and it needed a swap. I was shining the light on it and "ting" i watched it break in front of me. well after letting it cool off for over an hour I needed to get the mile I had left home so i fired her up and go home. the next day grabbed a new belt and thought lets feel all these pulleys just to make sure everything feels good before i start putting this belt on sure enough my crank pulley was in two parts so looks like that may have been my problem all along and was just holding on enough at times to be ok! new pulley is here hope to get it on this week sometime and swap a few more things!

 

For what it's worth, I'm getting the P1688 also in my 06...
Car had no codes when I bought it, but I can't trust that (this dealer also got me the car with a fresh inspection sticker - despite an HID that's fundamentally bad and window tint that isn't legal in NY).

Drove it home, but pretty mildly. Once home decided to give a good full-redline push to feel out the powerband, and probably just before 6k I went into limp mode, and CEL came on.
Turned it off then on, and the CEL stayed on but it drove like a top. I removed and cleaned both the MAP and TMAP, but probably not a great job- just spray blasted them and let them dry before I put them back. Cleared the code with my scanner.

A couple days later - gave it a rip, and this time I feel like I got over 6k, but it still popped into limp mode and the CEL came back on.

In my case - no noises, no power loss (other than limp mode), just high RPM causing the CEL and P1688. I'm suspecting it's my TMAP - I may try to clean it again since I have my first autocross in 15 years Sunday and I would be devastated if I went into limp mode mid-run (and I won't get a new TMAP sensor before that).

Since I'm new to this car - I've been eyeing these pulley upgrades. Am I correct that it would be smart to not just replace the top pulley with a reduced pulley, but to replace the bottom pulley to eliminate this other P1688 cause that I keep reading about? I saw a lightened pulley that was something like 88% lighter - I imagine that would be good for throttle response! It was one of the kits that came with the top pulley, bottom pulley, belt... intercooler boots for some reason... Anyone have thoughts on proactively replacing that pulley with a lightened one?

And anyone else who throws the P1688 with no noises / no power loss... Did replacing or cleaning the TMAP fix it?

 

Interestingly - I decided to replace the crank pulley with an ATI unit this week, since I was also tackling installing a smaller supercharger pulley this week. I also replaced the tensioner and a slightly smaller belt came with the pulley.

I was surprised to see that my stock crank pulley seems totally fine. Not failed, not split - looks perfect. See for yourself:



Also, things I tried in prior weeks, before doing this pulley/pulley/tensioner replacement:

• Twice, I've pulled the MAP and TMAP, and first attempt spray blasted them with MAF cleaner, second attempt sprayed then soaked the sensor elements in MAF cleaner for 15 minutes.
• My buddy who lent me his SC pulley puller gave me an extra MAP sensor (not the TMAP - although I've ordered one, hasn't arrived yet) to try.

I haven't had a chance since completing the swap last night to open it up and see if I'm still getting the P1688, but the fact that my pulley is fine makes me want to explore other reasons why I'd get a P1688 - in my case at about 1000 RPM before redline, with the accelerator pedal floored.
P1688 is more troubling from a safety standpoint (I was on the gas for a reason!), since it triggers limp mode. I definitely want to ensure this is resolved to a level of high confidence.

Where does the troubleshooting checklist go from here, when your pulley is fine, to resolve P1688?
Randomly ordering/replacing parts is never efficient nor confidence boosting - I'm sure you all agree with that.

 

I had a P1688 code in my JCW thread a few years back.....after changing and checking other parts that everyone said it was...turned out to be a bad T-Map sensor...found another one and it's been working fine since

Bryan