Thermostat

S

SCSI15

Member
:
2004 Mazda 3s 2.3l
Hey my MIL light came on again after replacing the coolant sensor thinking that was the issue.

Well lo and behold the theromostat code p0128 came back. I know I should figured it would if I read that code before replacing the coolant sensor.

Was hoping that would go away after that. Not the case, realized how much of a noob to this I am.

So anway apparently I have been running with the thermostat stuck open for a little over a year and half. Any harm being done with the engine running cooler than normal? I can't imagine since I haven't really had any issues
 
Running too cool can cause some damage because the ECU would think the engine needs more fuel. Long term excess fuel can contaminate oxygen sensors.

Clifton
 
Why the PCM update? Does a simple disconnecting of the batter not take care of it?
 
SCSI15 said:
Why the PCM update? Does a simple disconnecting of the batter not take care of it?
Click to expand...

nope. there are updates for these cars all the time, a new file is sent to the dealerships probably every 10 days or so. not every car needs every update its all based on your VIN. from my experiences about 90% of the time that i do a thermostat an update is required.


on a side note.

often times disconecting the battery can cause the pcm to require an update on early models, later models if the PJB is disconnected for to long an update will be required.
 
Would you guys recommend an update after doing a thermostat replacement?

How do I really know if my thermostat is stuck open? What if all I need is an

update? I checked with the dealer and they want 89 bucks....wow just to hit a button?
 
there are ways you can trick the dealer into checking for an update. is your car still under warrenty? auto? or manual?
 
I assume by TSB you're refering to the service book? or my car manual?

My car is no longer under warranty and it is a manual. More specific 04 mazda3 hatch with 106k on it
 
SCSI15 said:
I assume by TSB you're refering to the service book? or my car manual?

My car is no longer under warranty and it is a manual. More specific 04 mazda3 hatch with 106k on it
Click to expand...

tsb is technical service bulletin. you can find them online
 
flash75 said:
Technical service bulletins can be found here.

http://www.protegefaq.net/tsb/

I did a quick check and didn't find any Mazda 3 information about checking for PCM updates when a thermostat is changed.

Clifton
Click to expand...

Hey thanks dude I really appreciate that. I'll take a look, not expecting to find anything else than you did but sweet hopefully I won't need an update.

might be a stupid question but should you update your pcm everyonce and awhile? or only unless you have you or replaced something that needs it done?
 
SCSI15 said:
Hey thanks dude I really appreciate that. I'll take a look, not expecting to find anything else than you did but sweet hopefully I won't need an update.

might be a stupid question but should you update your pcm every once and awhile? or only unless you have you or replaced something that needs it done?
Click to expand...

I don't have the answer to that question. I have owned 5 vehicles with OBD II diagnostics and none of them ever received a PCM update. None have broken down or failed.
I'm still trying to comprehend why changing a thermostat would require a PCM update, since it's an ordinary mechanical device.

My feelings are that if the PCM should be frequently updated Mazda should pay for it. It's not something the owner has neglected, it's a little like your Microsoft XP needs updating (it's currently done automatically and at no cost to the owner) and being charged for the update. If the Mazda PCM needs updating they must have found a problem with it. They shouldn't place the burden of detecting it and on the owner and then require him to pay for for the update. My 2 cents.

Clifton
 
yeah thats a good point never really thought of it that way.

I still think its a little pain in the ass that mazda mounted their thermostat into a house that you also have to buy. Damn thing is going to run me 50 bucks from that mazda site. I guess thats mazda making their money
 
Changing the thermostat does not require an update or reflash. The reflash was to cure the re-occuring po128...assuming it is a programming correction of course.

Updates are no different than your home pc. There are problems that are unforeseen and corrected through software changes. You may never experience a situation where one is needed, but conversely you can need one that is discovered through troubleshooting.
 
Hi there, ive been trying to do some research on this code (p0128) my 02 proteges been coming up with relentlessly through this forum. Service writer spoke about a cure for the reoccuring po128 code and thats exactly what i need. Ive triede replacing just about everying that could be causing this code, ie thermostat, coolant sensor, air intake sensor, flushing fluid. So if anyone could fill me in on this "reflash" or offer any other insight it would be greatly appreciated because i really need to get rid of this code already.
 
this pcm reflash is done at a dealership? theyre gunna want me to pay? because i doubt its the thermostat again seeing as i recently changed it
 
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