rpolyak

Good morning, I am hoping someone can assist me with giving me a direction. But first a little history.


Mechanic # 1
a. Replaced Radiator (needed to be replaced)
b. 3 months after this replacement received the P0128
c. Replaced over flow canister
c.a did not resolve P0128
d. Replaced Thermostat and Water Pump
d.a did not resolve P0128
e. Replaced Both temperature sensors
e.a did not resolve P0128
f. Replaced Thermostat again
f.a did not resolve P0128


Got tired of working with 1st Mechanic (He also moved his shop so needed to find a closer alternative).


Mechanic # 2.
a. Could not find any issues Temperature running normal between 190 and 210.
b. He suggested Thermostat so I authorized
b.a Did not correct P0128


So I am now at a loss? I still have P0128, Temperature looks to be normal, but I still have P0128. I am waiting to hear back from Mechanic # 2 for he was to do some research? But I am at a loss? 1 1/2 I have had this dreaded P0128. Anybody else have any Ideas?


Thx

BimmerFan52

There are a number of reasons you could get a P0128 error, or engine coolant not reaching temperature within a preset time. One cause of the P0128 error is a defective heater coil in the thermostat, which is tested by the ECM at start up. In addition to the heater coil, the wiring harness to the thermostat must be intact and completing the circuit.

You can test your thermostat heater coil by removing the electrical connector on the top of the thermostat and measuring the resistance with a multimeter. It should measure approximately 14-16 ohms. If it measures 1 that indicates an open circuit and a defective heater coil.

Then you will need to physically examine the harness leading to the thermostat for any fraying or broken connection. There is a method for testing continuity of the harness by disconnecting both ends and using a continuity tester or multimeter to again measure resistance.

Other possibilities are engine coolant temperature sensor, intake air temperature sensor, thermostat stuck open (I think you have already addressed that) and a faulty cooling fan that is running too much (you will hear if the fan kicks on before the engine warms up or stays on all of the time).

rpolyak

So Just for kicks and giggles, I replaced the Air Filter.

So After driving the car after air filter replacement, within one day the P0128 goes away.

So this is one very expensive Air Filter.

twh

Did you replace the MAF along the way? If you Google P0128, it mentions that the Intake Air Temperature is part of the calculation for setting off P0128. I believe the IAT sensor is built into the MAF on this car. Perhaps the MAF connector wasn't all the way seated??

BimmerFan52

It is crazy how sensitive some of the electronics are. We can add it to the list of things to look for when the old P0128 comes up.

P0125 p0128 code could this just have been clogged airfilter : OBD-Codes.com

rpolyak

No I did not replace the MAF, but that was going to be my next step after the Air Filter.

pcy

My guess as to what happened to OP's car is that the MAF connector was loose (not fully latched) and contributed to that error. During the air filter replacement, MAF connector is pushed all the way in and that resolved the issue and the error is gone.

yelcab2

Well, my P0128 code has me trying:

BMW water pump
BMW thermostat (2)
BMW temp sensors in both locations.
Air fitler.
And the code keeps coming back.

There is one additional clue. I get zero heat during the first drive of the day, no matter how long I drive it, no matter how far I drive it.

What is next?

donpb

You have got to be throwing more codes than just that one. Are you using a generic OBD2 or a BMW specific code reader?

seanjordan20

What brand thermo and sensor are you using. You need a BMW scanner.