2EF4 code with Service Engine Soon
05-25-2023, 07:43 AM
#11
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OK,
1. Ignition ON, engine OFF, Thermostat connector disconnected, there is 12V on one pin, and 4V on the other pin (this is likely the pin from the ECU that is an open collector circuit).
2. Ignition OFF, engine OFF, thermostat connector disconnected, the 4V signal goes to zero since there is no more electrical current any where
3. Engine on and running, thermostat connector Plugged back in, the pin that was 4V before now bounces around from 12V to zero and then steadies out at >13V (battery voltage when car is running)
All I can conclude is the main ECU is controlling the thermostat by turning it on and off at start up. The thermostat seems to be dead (out of the box).
Since it is only $100 ish, I will replace it and see where we are.
1. Ignition ON, engine OFF, Thermostat connector disconnected, there is 12V on one pin, and 4V on the other pin (this is likely the pin from the ECU that is an open collector circuit).
2. Ignition OFF, engine OFF, thermostat connector disconnected, the 4V signal goes to zero since there is no more electrical current any where
3. Engine on and running, thermostat connector Plugged back in, the pin that was 4V before now bounces around from 12V to zero and then steadies out at >13V (battery voltage when car is running)
All I can conclude is the main ECU is controlling the thermostat by turning it on and off at start up. The thermostat seems to be dead (out of the box).
Since it is only $100 ish, I will replace it and see where we are.
05-25-2023, 05:08 PM
#13
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My Ride: 05 530i M54
Model Year: 05 530i
Engine: 3.0 M54
They do fail open. I have to look at that video. Now there are some that wasn't designed to operate as the OE/OEM. I have never worked on one that failed closed.
05-31-2023, 02:00 PM
#16
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My Ride: 2006 530xi touring
Model Year: 2006
Engine: 3 liter
More update.
After the new BMW thermostat went in, one day later, there was an engine code 2EF4 but not yet throwing a CEL light. So I decided to change the Engine Coolant Temp sensor at the top front of the head. The Coolant temp sensor at the out put of the radiator was already changed with the BMW thermostat. It's now five days later and more than 100 miles driven. There is no CEL light, there is no OBD2 permanent codes in the car, and the Service Engine Soon light stays off. There is a Pending code (not yet permanent) for Coolant Temperature below Thermostat Regulating temperature (P1287?) but this is not yet a code to cause the CEL. In the meantime, all Smog Monitors are Ready so I can actually pass smog if I wanted to.
Guardedly calling this a win, and the cause is the Engine Temperature Sensor.
After the new BMW thermostat went in, one day later, there was an engine code 2EF4 but not yet throwing a CEL light. So I decided to change the Engine Coolant Temp sensor at the top front of the head. The Coolant temp sensor at the out put of the radiator was already changed with the BMW thermostat. It's now five days later and more than 100 miles driven. There is no CEL light, there is no OBD2 permanent codes in the car, and the Service Engine Soon light stays off. There is a Pending code (not yet permanent) for Coolant Temperature below Thermostat Regulating temperature (P1287?) but this is not yet a code to cause the CEL. In the meantime, all Smog Monitors are Ready so I can actually pass smog if I wanted to.
Guardedly calling this a win, and the cause is the Engine Temperature Sensor.
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twh (05-31-2023)
06-13-2023, 08:22 AM
#19
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My Ride: 2006 530xi touring
Model Year: 2006
Engine: 3 liter
OK, again. The SES light came on, no CEL, just a permanent code P0128: Coolant temperature below regulated temperature. I have changed ...
Engine coolant temp sensor twice, the latest is a BMW branded one
Radiator outlet coolant temp sensor, Oreilly's branded one
Thermostat, twice, latest is BMW branded one.
Waterpump
Radiator.
I have checked fuses and 12V voltage at the connector to the thermostat. They are both there. Although, I do not know what voltage should be at the thermostat when engine is started up. So, I can't tell if it is right or wrong
I can use a scanner to activate the waterpump, so that is good electrically.
I am able to bleed the system using the BMW 12 minute cycle.
One last clue: While I was changing the the coolant temp sensor at the front of the engine head, very little coolant came out. So, I don't know what to think of it. Should there be a stream of coolant flowing out when the sensor is removed if the system is full of coolant, and it was?
Out of idea at this point.
Engine coolant temp sensor twice, the latest is a BMW branded one
Radiator outlet coolant temp sensor, Oreilly's branded one
Thermostat, twice, latest is BMW branded one.
Waterpump
Radiator.
I have checked fuses and 12V voltage at the connector to the thermostat. They are both there. Although, I do not know what voltage should be at the thermostat when engine is started up. So, I can't tell if it is right or wrong
I can use a scanner to activate the waterpump, so that is good electrically.
I am able to bleed the system using the BMW 12 minute cycle.
One last clue: While I was changing the the coolant temp sensor at the front of the engine head, very little coolant came out. So, I don't know what to think of it. Should there be a stream of coolant flowing out when the sensor is removed if the system is full of coolant, and it was?
Out of idea at this point.
06-13-2023, 08:47 AM
#20
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I do not think it is a problem that not much coolant came out when you changed the sensor. There has to be a vent path behind that coolant for it to come out. Sort of like the upside down coke bottle won't drain trick. When I changed the heater control valve about a year ago not much came out.