P1620 code, but thermostat just replaced

nickxtsui · Dec 19, 2011

hi bimmer fellows:

Now I have a P1620 code on my 2001 E46 325CI. I had a P0128 code a week ago, then I replaced the thermostat. Now I have a P1620 code which I found people thought it was the thermostat problem, but my thermostat was just replaced, which I got from ebay and the seller said it was a new one.

Is P1620 definitely indicating thermostat problem? I think my coolant has air inside, and I did get overheating, so ..... maybe this could be the culprit?

Any suggestion is highly appreciated. Thanks a lot folks.

jonathan2263 · Dec 19, 2011

As much as it s&cks, I would buy an OE thermostat from a reputable fest sponsor and replace what you put in. You never know what you get on eBay, and it sounds like you got a cheap, poorly made part.

1620 is a thermostat problem. It seems like an issue with the wiring or sensor. Deffinately areas likely to be bad on cheap parts.

jonathan2263 · Dec 19, 2011

Did you overheat before or after replacing the thermostat? Any time you work on your cooling system, you need to be sure to bleed it properly afterwards. 0128 wouldn't cause overheating, it means the thermostat is sticking open. 1620... I'm still saying get a good , non eBay thermostat.

nickxtsui · Dec 21, 2011

hi Thanks a lot for reply.
I did get a overheat problem after replace my thermostat. Then I bleed the coolant again, then everything seemed normal. I have been driving for about 300 miles, and so far everything was good.
However, when I read error code, I found the P1620 code was still there. How am I supposed to do with it?

mawana · Dec 21, 2011

Make sure both the thermostat and thermostat connector are fully seated/inserted! If both are snug, follow Jonathan's advice and get a new OEM thermostat from a reputable supplier...

nickxtsui · Dec 23, 2011

hi mac_wan, I think I checked the connector. Are you referring the temperature sensor hooking on top of the thermostat? I think it was correctly connected unless it was broken.
I also checked the two hoses connecting to the thermostat, they looked fine too. At least I did not see any leak from both sides.

rebmo · Dec 23, 2011

Hmm. Something tells me there is another problem throwing this code. I have seen a few posts like this with no resolution after Tstat change. My 06 with only 27k on it behaves perfectly normal from a heat/coolant level/engine temp at 12:00 noon, yet still throws the code every now and then. I do have a OEM Thermostat that I will swap in this spring and see if that kills this code. I suspect a weak link here in some sensor or a overly tight tolerance in warm up timing. Let us know if you get this resolved.

nickxtsui · Dec 23, 2011

I will try to replace a new thermostat and see how that works. I will post a new thread anyway after I replace it. It is however going to be while I suppose since I feel my car is OK right now.
Thank a lot for your thoughts. I really appreciate it.

rebmo · Mar 4, 2012

Did you ever resolve this issue?

nickxtsui · Mar 4, 2012

Yes, by replacing with a another thermostat.

It turned out the first thermostat I ordered was broken! Then they sent me the second one which was good.

PS: One way to tell if a thermostat is working or not is: feel the temperature of the induct and outduct of the thermostat. Simply touch them. Induct goes from driver side into the thermostat, whereas the outduct goes from the thermostat then down. If the thermostat works, then both ducts should be warm/hot after the engine is running. On the other hand, if the thermostat does not work, then only the induct is hot, which means the coolant is not circulating through the engine.

I hope I describe it clear, but forgive my English which is too far from my native language.

rebmo · Mar 5, 2012

Thanks for getting back. Your English is much better than my Chinese and acutally very good.

Good tip on the input/output temp check on the hose/housing.

My Thermostat is the original with only 28.6k/mi on the odometer now as I store the convertible during winter here in Wisconsin. When I start the car and warm it up, the temp gauge goes right to straight up and it stays there never going hot or cold from there. Yet I started getting the code P0128. I think when the dealer did a coolant flush they may not have bled it well. This was under the last part of the warranty and the problem arose shortly after.

Today I bled the cooing system and had the front up on ramps. It seemed to bleed some air out but overflowed a little when warm too. I cleared the code and we'll see if it returns. so far in a few starts it warms up and no code. I do have a OEM Thermostat to install and will probably do it when the weather warms a bit more and if the code returns.

Sounds like OEM Thermostat is the way to go. Glad to hear your problem is resolved.

Reb

nickxtsui · Mar 5, 2012

rebmo said:
Thanks for getting back. Your English is much better than my Chinese and acutally very good.

Good tip on the input/output temp check on the hose/housing.

My Thermostat is the original with only 28.6k/mi on the odometer now as I store the convertible during winter here in Wisconsin. When I start the car and warm it up, the temp gauge goes right to straight up and it stays there never going hot or cold from there. Yet I started getting the code P0128. I think when the dealer did a coolant flush they may not have bled it well. This was under the last part of the warranty and the problem arose shortly after.

Today I bled the cooing system and had the front up on ramps. It seemed to bleed some air out but overflowed a little when warm too. I cleared the code and we'll see if it returns. so far in a few starts it warms up and no code. I do have a OEM Thermostat to install and will probably do it when the weather warms a bit more and if the code returns.

Sounds like OEM Thermostat is the way to go. Glad to hear your problem is resolved.

Reb

Agreed. I'd think OEM is normally the best bet. Good luck.

csw8331 · Jul 18, 2013

ok, I need a little advice. I just replaced my thermostat a couple weeks ago after getting the P1620 error. (also did the CPS sensors and Vanos rings and the valve cover gasket)

Today while driving home got the SEs light and am now getting P1620 and P0444

I used a Genuine BMW replacement Thermostat, so do you think it is still a faulty thermostat or is there something else to check? Electrical connection looks good.

The P0444 I believe is the fuel tank breather valve so now I have that to address.

Any input would be appreciated.

P1620 code, but thermostat just replaced

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