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Discussion Starter #1 (Edited)
It's around 10F today in DC area, the coldest weather since I've been here 3 years ago. (The reason I say it's the coldest is... when I open the drawer to get the VAGCOM, the draw makes hiss noise; and the VAGCOM's cable was also frozen... Previously in a cold weather, only doors made hiss noise when opened.)

When I started my car in the afternoon at temperature 14F, I got an ECM related code
16990 - Internal Control Module: Processor Fault

P0606 - 35-10 - - - Intermittent
The car ran fine after I cleared the code and it didn't come back in the following trips.

I see some other post mentioning the same problem in cold weather. Don't know if any of you have similar experience? Will keep an eye on it.
 

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Is it possible that there might be some frozen moisture on the contacts of the plug to the harness? Maybe unplug and clean the plug and contact and apply some dielectric silicone before you hook it back up.
 

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Discussion Starter #3
I think frozen moisture is a strong possibility... Will try to clean the plug if the code comes up again. Thanks :)
 

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waterworld,

I hate to break it to you, but this is not a connector or external fault.

This is a ECU internal fault, usually a checksum type of error for the RAM module, but could be something else internally.

NOW, this being said, it could possibly be caused by a low Voltage dip during cranking as start up. This may have triggered an invalid logic state inside the ECU?

The other possibility could be defective RAM chip, cracked solder joint or defective capacitors.

The cold weather can bring out the worst in everything. Everything contracts so any questionable connection is at risk.

Would I take action at this point, not likely. I would take note of the situation and be on the lookout for any additional clues or issues like this that pop up again either at cold temperatures or otherwise.

Hopefully this was just a cold weather fluke that will not come back, but definitely be on the lookout for other similar indicators that may indicate a ECU failure.
 

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Discussion Starter #5
waterworld,

I hate to break it to you, but this is not a connector or external fault.

This is a ECU internal fault, usually a checksum type of error for the RAM module, but could be something else internally.

NOW, this being said, it could possibly be caused by a low Voltage dip during cranking as start up. This may have triggered an invalid logic state inside the ECU?

The other possibility could be defective RAM chip, cracked solder joint or defective capacitors.

The cold weather can bring out the worst in everything. Everything contracts so any questionable connection is at risk.

Would I take action at this point, not likely. I would take note of the situation and be on the lookout for any additional clues or issues like this that pop up again either at cold temperatures or otherwise.

Hopefully this was just a cold weather fluke that will not come back, but definitely be on the lookout for other similar indicators that may indicate a ECU failure.
jfoj, thanks for pointing out these possibilities. My heart is now much stronger to learn weird issues coming up, as the car is really old now...

I agree that if the microprocessor operates at a low voltage at start up, logic levels may be messed up or floating around to cause unpredicted problems... this can be a good explanation... as I recall the car on that day tried very hard to start (12-13 times, I counted), the battery may have a significant low voltage after generating sparks for so long time in addition to the low working temp.

- cracked solder joint, defective capacitors: that's not so bad :eek:

- defective RAM chip: do you mean the memory unit inside the microprocessor/ECM?
 

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jfoj, thanks for pointing out these possibilities. My heart is now much stronger to learn weird issues coming up, as the car is really old now...

I agree that if the microprocessor operates at a low voltage at start up, logic levels may be messed up or floating around to cause unpredicted problems... this can be a good explanation... as I recall the car on that day tried very hard to start (12-13 times, I counted), the battery may have a significant low voltage after generating sparks for so long time in addition to the low working temp.

- cracked solder joint, defective capacitors: that's not so bad :eek:

- defective RAM chip: do you mean the memory unit inside the microprocessor/ECM?
If you attempted to start the car 12-13 times, you may have had a low Voltage dip that might have made the ECU go somewhat stupid?

Everyone knows about restarting electronic equipment, what this does is drain all the capacitors in a circuit to get the logic back to a "known" state.

A low Voltage swing may have put the ECU in stupid mode, Voltage regulation may not be able to react well when the cranking Voltage is dipping/oscillating. You could have had Voltage dips below 8 Volts, most Voltage regulation circuits requires the supply Voltage to be at least 2-3 Volts above the regulated Voltage to stay stable.

Could be an issue with overall circuit board Voltage regulator problems. Possibly due to electrolytic capacitors that are aging and not up to spec/the job due to the cold weather.

As for cracked solder joints, well this sometimes in not always as good as it sounds. Many of the new chips are ball solder array and you cannot easily retouch to reword the solder joints. Also many of the modules in the car are dipped in a silicon or other type of water proof sealer that makes reworking a board very difficult. With the reduction/removal of lead in most newer solder, it is far more brittle, does not hold up to the expansion and contraction or vibration as well as older solder with lead mixtures.

RAM chip problems, does not happen often, but there can be problems with the EXTREMELY small wiring from the chip leads to the actual chip and/or micro contamination inside the chip or a micro fracture in the base silicon material that only shows up at extremely low temps.

Best course of action, hope it was a one off problem, and be on the lookout for any other similar symptoms that point toward a future ECU replacement.
 

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Discussion Starter #7
Jfoj, noted the information given with thanks.

BTW, for "start the car 12-13 times," I meant it clicked 12-13 times in one trial...

Oh, I realize I have a hot start problem for the engine... I also forget to post it in the forum... ==> here is my new post <==. Thanks!
 
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