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Hard Reset (Reboot) methods - What is the best one??

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Old 10-27-2011, 01:09 PM
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Default Hard Reset (Reboot) methods - What is the best one??

I like to know what is the best method for doing a Hard Reset (Reboot).
I think I may have performed it incorrectly.

I have been getting this P1638 DTC (CAN INST token message missing) - (montioring condition is ignition ON > 5 seconds) last week at 1st startup for 3 days in a row. See post# 12 in the following thread:

I used method #1 listed below, but I did not let the engine idle for 10 minutes.

I searched this forum thread for search terms - Hard Reset, also Reboot.
Here are the thread posting and information that were in the search results (I have assigned method numbers 1 though 4 to them):

DavidN Post# 2
hard reset information in a forum post (member DavidN):
Do the hard reset to re-calibrate the TPS.
- Disconnect both battery cables from battery
- Turn on ignition
- Turn off ignition
- Connect battery cables together
- Turn on ignition
- Turn off ignition
- Reconnect battery cables to battery
- Start the car
- Let it idle for about 10 Minutes
(Got your radio code? )
Sean B Post# 8
have you tried a hardreset? like a computer, but you disconnect the neg- cable on the battery, and hold it to the pos+ post for aprox 20 seconds. No keys in the ignition, have the radio code handy...
JagYi Post# 1
Next thing I read about was hardreset. So I disconnected the battery terminals and shorted them together for 10+ minutes. I tried to start the car and still no luck, same symptoms, same messages. Somewhere I remember reading leaving the terminals shorted overnight might do the trick. So I touched the pos and neg terminals together and put a heavy weight on top to keep them connected overnight.
Brutal post# 2
Disconnect the negative battery cable, and momentarilty touch it to the positive cable to provide a path to ground for the capacitors and erases volatile memory in the ecu's.

I could not find the pulling a fuse method. Maybe someone can post it in this thread.

Please post your comments and advice here in this thread.

I did the method #1 hard reset again this Tuesday morning. This time I let the engine idle for 10 minutes after the hard reset.

I had no problems since (only 3 days now).

Jim Lombardi

Last edited by jimlombardi; 10-27-2011 at 07:59 PM.
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Old 10-27-2011, 02:20 PM
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Talking Hard Reset

I vote for number 4, but number 2 is basically the same thing.
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Old 10-27-2011, 05:28 PM
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I guess the underlying technical question is, are there capacitors anywhere in the system which do not get discharged until and unless the ignition key is cycled? I wouldn't have thought so, but British engineering never ceases to amaze me....
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Old 10-27-2011, 07:32 PM
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Default Stamp out Voo Doo

My first question for Jim is- "why do you know the code when you first turn it on? Is there a CEL, or do you just turn it on with your scanner connected? Is there a symptom? Or is it just an atrifact of the scanner connecting as mine does many times as I connect?

To test what it takes to reboot the ECU, just look for P-1111 to turn to P-1000. I bet it is instantaneous. And what's with the remove both battery lead thing? So the car does not fill with too many p s or n s? Amd turning the key on part- It was either powered up with the key off, where it won't matter OR it was not powered up and the caps have sicharged. Soeey to seem so obnoxious, but there has been much voo-doo spread on the whole control system around here! And some by some otherwise very intelligent guys.

Just in case some of the modules do not have a series diode in the powere circuit, then shorting the wires might help- I do it. But my bet is that the ECU and the tcu have a series diode on the input lead and the shorting matters none.
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Old 10-27-2011, 08:27 PM
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Hi Ross
When I start the engine I get the CEL (check engine light). Then I turn the ignition off, then ignition to position II, then plugin the code scanner. I press scan and it found P1638 DTC code.

My list of hard resets are what I found when searching for the Hard reset instructions on this sub forum.
I only listed methods 1 and 3, I did not endorse them or recommend them. I was not sure how to perform the hard reset.

I used method 2 today and it did do the hard reset successfully.

Sorry if I upset you. I need your help with this recurring issue.

I started another new thread to try to get some help with P1638 problem.

Jim Lombardi

Last edited by jimlombardi; 10-27-2011 at 08:33 PM.
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Old 10-27-2011, 10:11 PM
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No, I am not upset- at least I don't think I am-... well maybe I am!
Seriously, i sure did not mean to imply that you were the one spreading Voo-Doo, but rather that you were the victim. Your posts are among the most factual and imformitive and I appreciate your efforts.

It sure sounds like you have the real deal CAN bus fault. I think someone else who had that found it to be the TCU module crashing the bus. As I recall, someone else decided it was the instrument cluster on his. Although CAN bus can be sniffed, it is a pretty complex task to do so. All stations on the bus share one channel, sort of like a n old party line phone. If one channel yells when he shouldn't, it disrupts the whole bus. If you unplug modules as it happens, you can probaly find the offender.

I bought a XJR TCU module for about $100 just for troubleshooting on flea bay. I believe this case is an exception to the rule to not throw part at a problem. Substitution is going to be the fastest solution, I'm afraid. If you have a scanner that scans the manufacturer specific codes, you might be able to see which module gives no response while an episode is happening.

Last edited by sparkenzap; 10-27-2011 at 10:15 PM.
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