P0128 check engine light code

[sufloyd]

Hello,

I'm getting a P0128 code on my 2003 V4 Camry. Autozone diagnosis says it's either
a) coolant low level
b) sensor not working correctly
c) thermostat not working correctly.

As part of 90k mile check about 3500 miles ago, the mechanic replaced the coolant. I didn't check the coolant after he had replaced it but I just checked it today and it's about 1 inch below the full level. Is this normal coolant usage considering that it's been about 3500 miles and 3 months since it was last filled?

If the coolant level is okay, then how do I figure out if it's the sensor/thermostat?

Thanks,
Kunal

[TRD VVTi]

Originally Posted by sufloyd

Hello,

I'm getting a P0128 code on my 2003 V4 Camry. Autozone diagnosis says it's either
a) coolant low level
b) sensor not working correctly
c) thermostat not working correctly.

As part of 90k mile check about 3500 miles ago, the mechanic replaced the coolant. I didn't check the coolant after he had replaced it but I just checked it today and it's about 1 inch below the full level. Is this normal coolant usage considering that it's been about 3500 miles and 3 months since it was last filled?

If the coolant level is okay, then how do I figure out if it's the sensor/thermostat?

Thanks,
Kunal

Code P0128 means that the coolant temperature is below the thermostat regulating temperature.

I doubt that you actually used coolant. I'm guessing that there was an air pocket in the system. Fill the coolant to the proper level and check for leaks. What is your engine/coolant temperature?

If the temperature is ACTUALLY low, you will need a new thermostat. If the temperature is ACTUALLY normal but the sensor shows it's low, you need a new sensor.

I'd start with filling the coolant up and clearing the code.

By the way. Your car is an I4 (inline 4 cylinder), not a V4.

Welcome to TN.

Here's cooling system link for you: http://www.camrystuff.com/manuals/Gen5/16_Cooling.pdf

EDIT: Note that the problem could be something else also. It could be a faulty ECM (computer), wiring, etc.

[JSM1284]

To add to TRD's explaination:

DTC P0128 COOLANT THERMOSTAT (COOLANT TEMPERATURE BELOW THERMOSTAT REGULATING TEMPERATURE)

CIRCUIT DESCRIPTION

DTC Detecting Condition

HINT:
This is the procedure of thermostat.

If the engine coolant temperature becomes less than 75 °C (167 °F) , it is abnormal.

If not due to the thermostat malfunction, it is abnormal.

Step 1 - 2
INSPECTION PROCEDURE

HINT: Read freeze frame data using the hand-held tester or the OBD II scan tool, as freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was

[Nad1370]

Replace your T-stat and properly "burp" the system and you should be all good.

[white07cam]

unless it is the sensor or some other thing then he wasted time AND money...

[sufloyd]

Originally Posted by TRD VVTi

Code P0128 means that the coolant temperature is below the thermostat regulating temperature.

I doubt that you actually used coolant. I'm guessing that there was an air pocket in the system. Fill the coolant to the proper level and check for leaks. What is your engine/coolant temperature?

If the temperature is ACTUALLY low, you will need a new thermostat. If the temperature is ACTUALLY normal but the sensor shows it's low, you need a new sensor.

I'd start with filling the coolant up and clearing the code.

By the way. Your car is an I4 (inline 4 cylinder), not a V4.

Welcome to TN.

Here's cooling system link for you: http://www.camrystuff.com/manuals/Gen5/16_Cooling.pdf

EDIT: Note that the problem could be something else also. It could be a faulty ECM (computer), wiring, etc.

Thanks for the tips. Basic question - how do I check the coolant temperature? As in, should I insert a thermometer in the radiator when the car has warmed up after a few minutes ? (but not after a long run, to prevent burns)

[TRD VVTi]

Originally Posted by sufloyd

Thanks for the tips. Basic question - how do I check the coolant temperature? As in, should I insert a thermometer in the radiator when the car has warmed up after a few minutes ? (but not after a long run, to prevent burns)

Checking the coolant temperature after a few minutes isn't going to do any good at all. After all, it takes quite a while for the cooling system to get hot.

What does your gauge read?

My Prizm (Corolla) had a coolant temp fault code and I noticed that the gauge was running lower than normal. I replaced the thermostat because of that and cured the problem.

[sufloyd]

Originally Posted by TRD VVTi

Checking the coolant temperature after a few minutes isn't going to do any good at all. After all, it takes quite a while for the cooling system to get hot.

What does your gauge read?

My Prizm (Corolla) had a coolant temp fault code and I noticed that the gauge was running lower than normal. I replaced the thermostat because of that and cured the problem.

Even after an hour's driving, the temperature gauge rises 2 notches up (and no more than that) from the C level. Does this mean it's likely a thermostat issue?

[njerald]

Originally Posted by sufloyd

Even after an hour's driving, the temperature gauge rises 2 notches up (and no more than that) from the C level. Does this mean it's likely a thermostat issue?

Yes, very likely as posted before.

[TRD VVTi]

Originally Posted by njerald

Yes, very likely as posted before.

+1

Unless of course, your coolant is so low that the temperature sending unit isn't reading correctly, or the sending unit itself is faulty.

There are still many different things that it could be, but I'm reasonably certain that your thermostat is causing the problem. Don't buy a cheap one. Just get it from the dealer. They're cheap enough anyways.