Hey all,

Just did a thermostat/water pipe job on my R56S, bone stock. It was leaking coolant all over the top of the bell housing, hence the need for the repair.

The short version
After swapped thermostat, car starts hard and throws P0117, goes into limp mode, runs smooth otherwise.

The longer version
I finished the repair on Monday, added coolant, car started fine and idled smooth that day. Did a short neighborhood shakedown run (didn't exceed 25 mph or 2.5k rpms) and it did fine, and I bled and topped off the coolant.

Next morning, got in the car to go to work and it cranked 6-8 times but didn't start. Cranked it again 3-4 times and it sputtered slowly to life, then settled into idle and ran normally. CEL was on, and the code reader pulled P0117 (engine coolant temp sensor low voltage). I cleared the code and the light didn't come back. On the road, I noticed it felt low on power, and getting on the highway it flashed the "limp mode" symbol, confirming what the butt dyno was telling me. Other than low power, the car runs and idles fine, and isn't throwing any other warning lights. Got to work and pulled the same P0117 code, even though the CEL wasn't illuminated.

I found this page, regarding that code, and it seems to describe the symptoms I'm getting:
https://www.yourmechanic.com/article...-jay-safford_2

So my thought is that the coolant temp sensor is bad, but my problem is that I don't know where that is. I understand that the thermostat housing has a bunch of integrated sensors - is the ECT sensor one of them? Is my shiny new thermostat going to have to be pulled again and replaced? Anyone know the correct method of testing the sensor after I've located it?

Thanks in advance for your help.

 

Update

I did some research and found that the ECT sensor is in the thermostat housing, and can be removed without removing the thermostat. So I pulled the "new" ECT sensor (that came in the new thermostat) and replaced it with the "old" sensor from the old thermostat. Reassembled everything and the car started up great - two cranks and it was running at normal idle. No codes thrown.

Weird thing is, on my shakedown drive, the limp mode symbol came up on the screen, although it didn't feel like it was down on power anymore. No codes from the OBD scanner, either.

Does anyone know if the limp mode light stays on until it is manually reset or something, or am I still in limp mode, but now with no explanation why?

 

Update 2

Took the car into work this morning (25 miles, part city, part highway, part backroads...my commute is kind of awesome...) and I noticed that it's definitely still in limp mode. It's making about 3/4 power, not really noticeable in town, but it definitely doesn't pull hard on the highway.

A few notes:

-The limp mode light came right on as soon as I started it
-It started fine, no excess cranking, no struggling to idle
-No CEL, and no codes active or stored (at least, none that my $15 code reader can see)
-It's running normally besides being short on power.

At this point I have no idea what to do, so I'll bring it into my indie to have him check things out unless anyone here has any other thoughts.

 

All i can think is check the wires and connections. When you change out the thermostat there are allot of wire in that main harness that can get bumped.

https://www.northamericanmotoring.co...hermostat.html

 

When i did mine on the N18 engine, i had the same thing. Stubborn limp mode...turns out that i flipped coolant hoses going to the radiator..lol i flip them back and issue when away.

So check your hoses.

 

embiggenedmini,

just curious, did you use oem thermostat or aftermarket, and if aftermarket what brand?

 

embiggenedmini,

Any update on this? I'm dealing with a stubborn P0117 after a thermostat housing replacement as well. The mechanic put the wrong housing in at first. Threw codes and fan running after car was off. He replaced the housing with what he believes is the correct one, and I still have the code.

Would love to hear how you resolved this problem!

 

My problem turned out to be the electrical connecter on top wasnt staying together right

 

Thanks Jeff - Do you mean the connection between the wiring harness and the coolant sensor isn't tight? Or was there a broken wire in the harness?

 

the connector wasnt staying on tight, maybe the connect is broke a little? i used a lil tape as a temp/permanent solution