I've come across various threads regarding rebooting ECU/TCM by disconnecting negative battery terminal and briefly touch it to the still connected positive terminal. Is this risky?
Appreciate advice.
Cheers

 

It will only reset the learned values in the PCM. The TCM is unaffected.

It also clears the OBD monitors, which are used for smog checks.

There is normally no reason to do it.

 

JagV8 thanks for the advice. Have done some work on her and heard that its essential to reset things. Would going to Jag to get reflash help much?
Cheers

 

Why do that???

Why can't you let it be? What is it you've done???

And you've given NO car details

 

[QUOTE=rjesq;1890682]JagV8 thanks for the advice. Have done some work on her and heard that its essential to reset things.[QUOTE]

false. Popular myth.

 

You'll need a higher level scan tool that can read all of your Jags ECM parameters.

 

My apologies JagV8..I have 2009 Jaguar XF Supercharged.80K. All my issues stemmed from a damaged expansion tank. I replaced with new but started to get the RP mode. Code P2601. Replaced the auxiliary coolant pump as it was old and seemed to be the reason for over heating the intakes. Following this i was getting the same code along with (CIRCUIT RANGE PERFORMANCE). Checked fuse which was ok but put in new one anyway. Car drove ok until i hit long hills then it would go into RP mode temporarily and would clear after restart. This caused the dreaded hose under the supercharger to give up. That was a mission but enjoyed the task of replacing it along with other hoses while there plus a new gasket. I must have done something right as i could then hear the supercharger for the first time. Car drove very well, until it got hot. I have recently done oil change and coolant flush. New Thermostat and housing. New intake ducts too which helped small vacuum leak. EGR valve is also new plus MAP sensor. MAF's are 1 year old. That is a list of work that has been done in a short space of time. This is why i was curious about rebooting the ECU..
I am going to avoid the battery connection thing but would welcome your advice after hearing all that i've done..
PS. would you happen to know which relay and where it is located for the auxiliary coolant pump?
Cheers

 

Looks like P2601 is not the aux pump. It's the SC pump.

Without good reason, I'd just let the PCM do as it likes.

 

Thanks JagV8..I will inspect the SC pump.Hoping its the issue..
Cheers

 

Given your symptoms and mileage, I would say the SC pump would be a good starting place to look for the real problem.

 

How many pumps does a car really need!!! Well i just found the SC pump after replacing the aux coolant pump twice being told that was the issue.(P2601). I removed the front bumper,which was easy only to find this pump. I also noticed there are 3 radiators from large medium to small. So replaced the SC pump and hey presto the headers stay cool. Problem now is i think they are staying too cool. Supercharger stopped whizzing. Can the heat reduction prevent the SC from working correctly?

 

No.

 

Ahh, this is called a dead short and is basically how wielding is done. So yes this is risky.

 

No, you don’t weld by taling the power source out of the loop.

Geez.

 

Nope welding is a function of controlling current. But since any controls on battery current will be removed when touching the - cable to directly to + side of a connected battery, YOU WILL GET THE FOLLOWING =
DEAD SHORT CIRCUIT MEANING
"A dead short is when an electrical circuit has zero resistance. This can result from the "hot" electric feed coming in contact with a metal object, like a metal outlet box or with the ground or neutral wire. Your initial sign that you may have a dead short will be a tripped breaker", Or blown fuse and/or burned component.

But lotus feel free to post up a video of you proving out nothing will happen by touching the - cable to the connected positive side of your battery on any of your vehicles.

 

You ether don't understand the concept of the jaguar hard reboot or your being facetious. There is no short of the battery circuit ! yes there is a short of the capacitors , but that's the whole point of the reboot , it's a part of powering down all the memory of the modules . I've done it plenty of times to cure the occasional funky module , genrally caused by low voltage starts . (I leave the sterio on a lot) mostly with positive results .

 

As my post says dats, what I quoted is the GOOGLE definition of a "Dead short", Myself and a Regional Coordinator have said your so called "Jag hard reboot" is good for nothing, and it's not recommended ANYWHERE in my version of the 2010XF manual. Having said that, dats maybe your time would be better spent trying to figure out why LEAVING ON YOUR STEREO IS CAUSING YOUR LOW VOLTAGE STARTS?..LOL

 

its me mate , i leave it going on purpose to listen to it .

its a good yard stereo .as well as a car stereo .
just some times a module will loose its place on start up . and the hard reboot some times is the way to put it in its place .
not saying it works on the XF , but it cant hurt .