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Discussion Starter #1
Check engine light came on after some heavy acceleration onto the freeway along with the engine feeling rough. At some point I looked down as the temp gage needle was moving back to the left to the normal straight up position.

After getting home and restarting the engine the Check eng light was off but my Peake tool found three codes:

Map Controlled thermostat circuit/control
Misfire, random/multiple cylinders
Misfire, cyl #4

I switched the coils from number 1 and number 4 cylinders. (The front drivers side cylinder is number 1, correct?)

I drove the car the next day and on the way home Check eng light returned and more rough running. Codes were:

Map Controlled thermostat circuit/control
Misfire, random/multiple cylinders
Misfire, cyl #4
Misfire, cyl #5

I pulled the plug connected to the thermostat and the readings from the coil in the thermostat was 12 ohms and the there was 12 volts on one of the leads to ground. The other lead did read to ground, but there was some resistance and when I switched to volts, there was a reading of 3 volts.

I am confused. Any thoughts?
 

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4th BMW
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474 Posts
Yes !!!

Lol, I've been thinking about my thermostat and that happened to me several hours ago. started stalling at traffic lights. Came home, put it on the battery charger (said it was at 53% but battery 12.3v). See what happens. My service engine/ 8C code is back....I have a 2014 battery and t-stat, 30k mi. and an expansion tank (BMW) blow out last July. See my other thermostat posts...BTW +- 12 ohms is OK for that reading
 

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2001 BMW E39 540i Automatic Sedan, 192 K miles
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1,588 Posts
Replace your thermostat, with an oem (Behr is the brand name).
 

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4th BMW
Joined
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474 Posts
My T-Stat is a BEHR OEM installed 10/2016

I could not get a good reading today for resistance across the T-Stat terminals.....maybe my overheat problem last July (cracked expansion tank) is kicking in. That said, I cleared the 8C code and a host of other codes70's and 83 (Peak) that go nuts when I started in Failsafe program. Then, I started the car smoothly drove off to my prior errand with absolutely no problem at all. Lol. I'm ordering a new thermostat Monday !!
 
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