Avec

I am throwing a code P2181 and it will immediately return after clearing. It would seem that at least some time would need to elapse for it to sense a discrepancy before coding if the sensor is working correctly. I thought I would change the sensor before diving into the thermostat. Anyone have the correct part number for that sensor?

Rossi

P2181 Is not related to sensor, it is your thermostat being stuck in the open position, you need to replace it. This is a notorious problem for many 955/957 Cayennes. There quite a bit of information on the forum regarding this.

Avec

The code is not thrown by the thermostat itself, but by the DME comparing cooling values from the temperature sensor at the thermostat and the sensor at the radiator. While the code would generally indicate a stuck open thermostat, I am seeing two things that don't mesh. 1) the code is being thrown immediately at start up (after resetting), giving almost no time for the temperature difference to be measured unless one sensor is indicating something vastly different than actual. and 2)I am seeing no indication of stuck thermostat with regard to engine warm-up. Temperature comes up as quickly as it always has.

My car may need a new thermostat. However, I would like to rule out a faulty temp sensor first.

Libast

1) The code may be stored to the fault memory
2) This fault is stored if the engine is not heated from below 40 °C (104 °F) to over 60 °C (140 °F) after throughput of a defined mass air flow.

Avec

So, it is not a temperature comparison, but a measure of actual against anticipated based on MAF throughput?

Andy E.

As Rossi stated, if the P2181 code shows up, the chances of a stuck thermostat are extremely high. I had the same issue on my GTS and a thermostat replacement rectified this problem.

Libast

Correct. Your ECU is telling you that the engine isn't getting to spec temperature as quickly as it should given the circumstances.

I have the same code I just haven't had the desire to replace it yet.

pbarch1

I've been throwing this code too. With no accompanying codes.
When it's cleared it takes several days to several weeks for it to reappear, think is's still the thermostat ?

transam

Hello there! Curious if you resolved the issue? My friends 09 GTS has the same exact issue and i just spent all day replacing the t stat and related parts. Still the CEL comes on instantly after clearing codes and starting. Im going to shotgun a sensor at it next. Thanks in advance! John
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transam

Answered my own question. Found there was an air pocket and the coolant was below the MIN line in Rez tank. Yes, this will set the p2181 code. I topped off and the light went immediately out. I had reset the light 6 times prior during the test drive. Would come right back on. Topped off, did not even have to reset code. Turned engine on and light was not on. For future references to googlers like me.

TomF

Glad you got it sorted out.

I too have had the same error for a while and know that it is caused by a bad thermostat and weeping water pump. I have been putting it off for few months as the coolant level stays pretty constant and I have other priorities right now. This will be the third thermostat and water pump in 108k... the first at 39k, the second at 74k. They are all factory parts, so I wonder if the previous owner's techs failed to install them correctly and ensure good seals. I have all the parts ready to go, so I'll tackle it in the coming weeks.

Jd_gts

Care to elaborate on the air pocket? I threw this code and upon topping off the coolant reservoir, the light went away... but then it came back on a few days later. I checked the reservoir and it is showing full still, but wondering if maybe there is an air pocket somewhere? Or perhaps I need to just break down and do the thermostat. I've heard it is quite the job to complete. I just don't want to end up in the same situation as you, where you spend all day replacing if it's an easier problem to fix. Are you sure the problem wasn't the thermostat, but the light came back due to an air pocket related to the refill? Any advice appreciated!

NelaK

I believe the Cayenne should automatically bleed the coolant loop as long as the coolant level is where it should be and there are no leaks allowing air to get in.

As far as replacing the thermostat goes, I did mine a few months ago and it wasn't too bad honestly. If I recall correctly (on my 957 CTTS at least) it was basically just: remove the intake hoses from the front, move a few wires out of the way, remove the water pump, spend the next few hours yelling and cursing as I fight with getting the old thermostat out, put everything back together, top off the coolant. I replaced the water pump, thermostat, thermostat housing and serpentine belt all at the same time I believe. Took maybe an evening?

As far as the light itself goes: its based off the ECU measuring how fast the engine is warming up over a period of time. Its not a direct measurement of anything, but I can easily see that metric being reset if the car senses the coolant level has changed (I'm not 100% if the coolant level sensor would detect a top up or not though so maybe not).

TRINITONY

If you’re only replacing the thermostat don’t bother removing any hoses or draining the coolant. In fact just move the water pump to the side leaving it behind the radiator. Then don’t go fighting with the thermostat to remove it. Just drill a hole in the gasket in two spots and you’ll be able to pop it right out. Should take u about 30 mins or so.

NelaK

Ugh. Yeah. I fought with it until it broke and then it came right out. Same thing but a lot more effort I guess.