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Andrew Martin
Andrew Martin,
Category: Hyundai
Satisfied Customers: 233
Experience:  Technician at Wile Hyundai
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Are you online, I need a second opinion on 2008 Accent.

Customer Question

Are you online, I need a second opinion on 2008 Accent. Replace bent valves due to timing belt break, changed out all sensors (crank, cam, osv, coolant temp sensor) plus timing belts, drive belts, tensioners, cam/crank seals). Car runs awesome, but I cant make P0128 go away, keeps coming back after 50 miles of driving. Checked many times the coolant level, took out thermostat (OEM) and it opens at 180 over the stove.
When I check the circuilt connection to coolant temp sensor, here is what I got. Multimeter blk pin to ground/negetive terminal and red pin to pink wire going to coolant temp sensor:
Car off, sensor disconnected: 0 volts
Car on, sensor disconnected: 5.5 volts
Car off, sensor connected: 0 volts
Car on, sensor connected: 3.1 voltsThe sensor runs around 190 degrees at operating temp, I checked with infrared thermometer.When I checked coolant temp sensor with car under 70 degrees, at start up, the voltage jumps around alot and after 5 mins it stablizes, if you need those specs, I can get them.What do you think? I here this car needs a ECM update but if so, shouldn't have set code before the timing belt break?I have spent many hours on this , I dont have professional grade scan tool just basic one, does not show time code was set or temperatures, or any other details.
Submitted: 9 months ago.
Category: Hyundai
Customer: replied 9 months ago.
For reference of voltage and time only, PLEASE NOTE, I FOUND OUT AFTER I RAN TEST THIS THERMOMETER WAS NOT WORKING, SENSOR WAS MUCH HOTTER THEN INDICATES.
Customer: replied 9 months ago.
https://www.youtube.com/watch?v=1_O5wiE4j4s
Expert:  Roy replied 9 months ago.

good evening my name is ***** ***** I will assist

180 thermostat is too low. it needs to be 195. the pcm looks for this temp for the engine control system. if it does not reach the correct temp, it will set this code. once you get the temp up to specs the code will not set.

I read the other posts you have sent and all the coolant sensor readings are good. it is not wiring or pcm

Roy

Customer: replied 9 months ago.
Ok well, my problem is this: 180 degrees is the only temp available for this car's thermostat, there is none available I looked for a different temp....
Expert:  Roy replied 9 months ago.

did you check the dealer???

Roy

Customer: replied 9 months ago.
sir, 180 is OE spec and only available.
Expert:  Roy replied 9 months ago.

then my info is wrong. my info calls for a 195 thermostat.

Roy

Customer: replied 9 months ago.
Can you please close the question? or open it if you want the feedback....
Expert:  thomas hill replied 9 months ago.

hi my name is ***** ***** you have accses to a scan tool?

Expert:  thomas hill replied 9 months ago.

to see whet the coolant temp is currently reading

Customer: replied 9 months ago.
a common one, I cant see details on the code , temps or when it was set?
Customer: replied 9 months ago.
I meant that to be a period)
Expert:  thomas hill replied 9 months ago.

what would also set this code is a bad connection to the temp sensor if you can inspect the pin connectors to see if they are not making good connection

Customer: replied 9 months ago.
ok I can do that, I was wondering the same thing....especially if I changed the sensor, which I did when I did all the engine work.....I did use sensor spray cleaner (not carb cleaner), but maybe a little di electric grease? If it helps the code always comes back at 50 miles and its P0128, along with P0128 pending...I just cant help but to think it is something simple, but hard to miss....There isn't alot of info for this problem online , if it was a common problem I would think the car being a 2008, it had all these years to come up with other people
Customer: replied 9 months ago.
http://www.myhyundaiforums.com/10-01-004.pdf
Expert:  thomas hill replied 9 months ago.

ok i just found a pcm update for that code the pcm will have to be updated by a kia dealer its tsb# *****

Expert:  thomas hill replied 9 months ago.

i will try to send you the tsb hold on

Expert:  thomas hill replied 9 months ago.

here it is take a look

Customer: replied 9 months ago.
I know it has a tsb but that may not fix the issue, correct?
when I did the voltage testing , as you are aware, the voltage was jumping around, I thought that was quite strange how it jumped so much, have you ever seen that on a coolant sensor issue? Really I am trying to eliminate some of the unknowns....
Expert:  thomas hill replied 9 months ago.

i know the voltage was jumping around but the coolant temp sensor should be tested in resistence i will send you a test diagnostic for your car but i do think that you should have the update done before you get to crazy into it sometimes the simple things are the fix.

the resistence for that coolant sensor is at 68 degrease the resistance should be 2.31- 2.59

let me know what you find

Expert:  thomas hill replied 9 months ago.

Nice Ya that's the Hyundai one that's the one you need. I think if you do that you will fix the problem

Customer: replied 9 months ago.
are you online? I need to know which pins on the sensor to test for resistance.....thanks
Expert:  thomas hill replied 9 months ago.

Looking it up now

Expert:  thomas hill replied 9 months ago.

Here it is

Expert:  thomas hill replied 9 months ago.

Let me know if need anything elts

Customer: replied 9 months ago.
I ran engine to operating temp with a good constant rev....I realized that two of the factory clamps on the thermostat housing leaked a little, I am thinking that this leak is creating air vacuum on cool down and letting air into cooling system, could this be enough to cause P0128 code?
Expert:  thomas hill replied 9 months ago.

i don't think so its common for all kias of the year range to leak around the clamps a bit we change the clamps to screw type clamps

Customer: replied 9 months ago.
are you familiar with the coolant sensor readings for voltage? I did the test to check voltage, and used a infrared themometer, i can send you those results:https://www.youtube.com/watch?v=yRkCs6NOeus
Customer: replied 9 months ago.
coolant temp sensor after cold start:
30 seconds: 70 degrees (F)
1 min: 79
2 min: 85
3 min: 102
4 min: 116
5 min: 118
7 min: 136
8 min: 145
9 min: 149I am aware these are very low readings at the sensor, please see video for voltage at sensor.
Customer: replied 9 months ago.
I also checked the inlet and outlet of the thermostat housing (coolant enters and leaves radiator hoses here), the inlet/outlet are metal so should be good transfer of heat from coolant, those readings where almost the same, and also very low...
Expert:  thomas hill replied 9 months ago.

you can't test the sensor reading voltage you have to use resistance

Customer: replied 9 months ago.
test sensor using resistance when the car is running? I was told that voltage will change at the sensor according to heat of coolant, to verify engine is warming up within specs....
I used a infrared thermometer to read temps of the sensor at various points of time to compare to voltage...
Customer: replied 9 months ago.
Pretty lame "expert" leaves middle of thread, if I could leave this guy one star I would....dont take the question if your not going to help or at least let me know you dont know the answer........
Expert:  Andrew Martin replied 8 months ago.

Hello, this is how you check the engine coolant temperature sensor from the Hyundai service manual. With the ignition OFF, disconnect the engine coolant temperature sensor connector. Check resistance between pins 1 & 3 on the sensor, not the harness. If not within specification, replace the engine coolant temperature sensor. I have supplied pictures to assist you.

Customer: replied 8 months ago.
The sensor (this is a brand new sensor) was at about 2.0 resistence at about 70 degrees (very rough estimate), I bought another new one and it test around the same. I believe the coolant is not getting hot enough, I am replacing with a new factory thermostat, although I know the one in the car opens at 180 (stove test) I believe the pressure of the water pump is pushing the coolant past the thermostat.
Expert:  Andrew Martin replied 8 months ago.

Alright, remember that the resistance measurement is in kilo ohms so it should roughly 2.3-2.6 K ohms at 68 degrees. Make sure you bleed the system very good too, if you don't have a spill free funnel then open the radiator cap half way and keep topping up the reservoir. Squeeze the hoses also to work the air out, and make sure the heat is on but the fan on the lowest setting. Let me know how it works out.

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