P1620 - Map Cooling Thermostat Control Circuit Signal High

[dellop]

The MIL has come on intermittently twice over the last few months, so I propped for a code reader since I don't have an AutoZone etc in my area.

First time I read the codes I got two back:
P0344 & P1620
I cleared the codes and now the only one that has come back so far is:
P1620
Which I read as maybe a bad thermostat within the cooling system. Is this correct?
Also, does anyone have any sources to purchase one of these? Dealer only maybe?

Thanks for your help!

[441tech]

Where is your coolant temp. gauge reading at operating temperature? Does it look normal?

The E46 has a heated probe right at the thermostat.

[dellop]

Temperature gauge on dash looks normal.
-Right in the middle at operating temperature.

Oh, and I see I didnt put what car we are talking about. I have a 2001 325xi Sedan.

[441tech]

Ok, the only thing between the DME module (Digital Motor Electronics) and the fuse is the Characteristic Map Cooling Thermostat. If you had a problem with the module or the fuse, it would throw a different code. But, it knows it's there and operating, just operating incorrectly. This leads right to the electrically heated thermostat.

I'd say go ahead and change the thermostat. Just make sure you get the whole assembly including the heated probe and everything. I'm not sure how they sell it. And if it makes you feel any better, I'm basing all this on the factory wiring diagrams and service manual.

Let me know how it goes.

441tech

[dellop]

Thanks for the info.

I will do some further research as to where to get the partd and get back to you.

[dellop]

Another question.
I am looking through the Bentley Manual here and see that to replace the thermostat you need to remove the cooling fan, which to remove, you need to remove the front bumper (automatic transmission).
Anyone have experience with removing the bumper? Is this something that a weekend do-it-yourselfer who is good at following directions would be able to do? Engine parts don't necessarily bother me, but body work does

[325isBaby]

What are you talking about, you DO NOT need to remove the bumper to remove the cooling fan it is talking about...you need to remove the belt driven fan (the one closest to the thermostat) My advise is KISS (keep it simple stupid) or better yet take it to someone who knows what they are doing!

[441tech]

Actually, if you have a long enough wrench, all you have to do is get the engine driven fan out. I believe it's about 1 1/4 in. wrench, or close. Just remember the threads are LEFT HAND--which means right loosy-left tighty this time. Leave your accessory belts hooked up and a sharp, quick movement of the wrench should snap the fan hub loose. You will also remove a plastic rivet and a screw in the top of the fan shroud. The engine driven fan and the shroud will slide right out together. Of course, this is all after removal of the air cleaner duct.

No bumper removal required.

441tech

[dellop]

Awesome.
I see in the manual it says to remove the "cooling fan" but doesnt specify which one. I see the fan you are talking about (Viscous clutch cooling fan) and it all makes sense now.

Thanks again for your help. I plan to order the parts tomorrow.

[441tech]

No prob. Let me know how things work out.

441tech

[dellop]

Is there any other way to snap the fan hub loose besides the "BMW special tool"? I have tried a quick movement clockwise, but it will not snap loose.

[dellop]

Originally Posted by dellop

Is there any other way to snap the fan hub loose besides the "BMW special tool"? I have tried a quick movement clockwise, but it will not snap loose.

FYI
I ended up using a rubber mallet to get it to kick loose.

[441tech]

When all else fails, grab a hammer. Glad to hear of progress.

[dellop]

Well, got the thermostat today, put everything back together, and she runs. No errors being kicked out yet, I will drive around more tomorrow but so far so good!

[441tech]

Cool!