Code P20B2
- Thread starter rgf451
- Start date
I'm in Detroit, away from my database, so I can't give you as detailed an answer as I'd like.
The coolant shutoff valve controls a coolant loop through the DEF tank / injector. Keeps it from freezing. I have not seen this code in a while, which might mean that software updates have "fixed" the trucks I regularly see. Or it could be that the valve is legitimately getting stuck open or closed. No idea, I can't look up the code definition right now. It might just be anecdote, but this code pops up when the weather first turns cold. Perhaps dormant valves that have long seized are asked to operate but can't respond. Maybe.
Anyway, the valve is located directly above the dosing pump. Clamp the hoses or you'll release coolant everywhere. Or be fast about it. It's simple enough to replace.
One minor problem you might run into is if the thing has gone into limp mode over it. You'll have to clear the codes in the ecu and dcu, and clear the scr-related history in the ecu to reset everything.
I'm pretty sure most of this answer is correct.
I'll probably edit it later.
The coolant shutoff valve controls a coolant loop through the DEF tank / injector. Keeps it from freezing. I have not seen this code in a while, which might mean that software updates have "fixed" the trucks I regularly see. Or it could be that the valve is legitimately getting stuck open or closed. No idea, I can't look up the code definition right now. It might just be anecdote, but this code pops up when the weather first turns cold. Perhaps dormant valves that have long seized are asked to operate but can't respond. Maybe.
Anyway, the valve is located directly above the dosing pump. Clamp the hoses or you'll release coolant everywhere. Or be fast about it. It's simple enough to replace.
One minor problem you might run into is if the thing has gone into limp mode over it. You'll have to clear the codes in the ecu and dcu, and clear the scr-related history in the ecu to reset everything.
I'm pretty sure most of this answer is correct.
I'll probably edit it later.
According to the book, the def tank sensor or the engine coolant temp sensor could be faulty. Or there could be a blockage in the cooling system. Here are some values.
Remove the seven 12mm bolts that attach the rh 1/4 fender, cut the wheel hard left and look above the DEF tank under the cab. You should see a valve with 2 coolant lines attached to it, and a 2 wire connector. In my experience I find it is the DEF tank semp/sending unit reading higher than normal temps. When that happens the ECU thinks the valve is stuck open, allowing operating temp coolant through the valve. The coolant valve should shut off at 46 degrees. If you feel the DEF tank and it feels very hot,it may be a faulty valve. I copied and pasted this tech tip it may help you.
DESCRIPTION OF CONDITION Most SCR (selective catalyst reduction) coolant cutoff valves received through warranty return do not reveal any faults when tested. Please follow the checks outlined below before replacing the coolant cutoff valve: When testing the cutoff valve function with the DXII (Diagnostic Explorer 2), the valve may not click if SCR related DTC’s are present in the engine ECU or DCU. Also, if the valve is unplugged any time while the ignition is on, the DCU will disable test function of the cutoff valve. In order to enable the cutoff valve operation, ensure the valve is plugged in and perform the UREA SCR System Memory Reset. From the Engine ECU Data Monitor and Active Test menu, select Active Test Setting> UREA SCR Related Memory Reset> then follow the prompts to complete the reset. After performing the SCR reset, clear DTC P204F from the engine ECU, and cycle the ignition off for 60 seconds. Turn the ignition on, and then read out DTC’s in the Engine ECU and DCU. If no DTC’s are present, the cutoff valve function test can now be performed. If the cutoff valve clicks when performing step 8 of the current diagnostic procedure in the Workshop Manual, it is NOT likely that the cutoff valve is faulty. When testing power or ground to the cutoff valve, the valve must be plugged in or the DCU will not apply power to the cutoff valve when an open load is detected. Once an open load is detected, a UREA SCR System Memory Reset is required, as mentioned above. If necessary, power and ground to the valve can be tested by back-probing the terminals with the connector plugged in. DTC (Diagnostic Trouble Code) P20B2 may falsely set in the DCU (Dosing Control Unit) due to an inaccurate temperature input from the DEF sensor unit’s temperature sensor. If DTC’s P205B, P205C, P205D, or U02A2 have set, diagnose these DTC’s before suspecting an issue with the cutoff valve. If DTC P20B2 is the only DTC set, use the Hino DXII (Diagnostic Explorer 2) to access the DCU data monitor parameters for the DEF tank temperature sensor, DEF pump temperature sensor, and the engine coolant temperature sensor when the engine is cold (at ambient temperature). These three parameters should be within 14 degrees Fahrenheit (8 degrees Celsius) of each other. If one of the temperature inputs appear incorrect at ambient temperature, diagnose the issue with that temperature sensor input first before suspecting a faulty cutoff valve
DESCRIPTION OF CONDITION Most SCR (selective catalyst reduction) coolant cutoff valves received through warranty return do not reveal any faults when tested. Please follow the checks outlined below before replacing the coolant cutoff valve: When testing the cutoff valve function with the DXII (Diagnostic Explorer 2), the valve may not click if SCR related DTC’s are present in the engine ECU or DCU. Also, if the valve is unplugged any time while the ignition is on, the DCU will disable test function of the cutoff valve. In order to enable the cutoff valve operation, ensure the valve is plugged in and perform the UREA SCR System Memory Reset. From the Engine ECU Data Monitor and Active Test menu, select Active Test Setting> UREA SCR Related Memory Reset> then follow the prompts to complete the reset. After performing the SCR reset, clear DTC P204F from the engine ECU, and cycle the ignition off for 60 seconds. Turn the ignition on, and then read out DTC’s in the Engine ECU and DCU. If no DTC’s are present, the cutoff valve function test can now be performed. If the cutoff valve clicks when performing step 8 of the current diagnostic procedure in the Workshop Manual, it is NOT likely that the cutoff valve is faulty. When testing power or ground to the cutoff valve, the valve must be plugged in or the DCU will not apply power to the cutoff valve when an open load is detected. Once an open load is detected, a UREA SCR System Memory Reset is required, as mentioned above. If necessary, power and ground to the valve can be tested by back-probing the terminals with the connector plugged in. DTC (Diagnostic Trouble Code) P20B2 may falsely set in the DCU (Dosing Control Unit) due to an inaccurate temperature input from the DEF sensor unit’s temperature sensor. If DTC’s P205B, P205C, P205D, or U02A2 have set, diagnose these DTC’s before suspecting an issue with the cutoff valve. If DTC P20B2 is the only DTC set, use the Hino DXII (Diagnostic Explorer 2) to access the DCU data monitor parameters for the DEF tank temperature sensor, DEF pump temperature sensor, and the engine coolant temperature sensor when the engine is cold (at ambient temperature). These three parameters should be within 14 degrees Fahrenheit (8 degrees Celsius) of each other. If one of the temperature inputs appear incorrect at ambient temperature, diagnose the issue with that temperature sensor input first before suspecting a faulty cutoff valve
Drain the coolant from the block and radiator. Or pinch off the coolant lines at the valve with hose clamp pliers, otherwise you will take a coolant bath. If it is in a derate you will need to have the SCR memory cleared by a dealer unless you have DX2 software. Otherwise its just nuts and bolts. Good luck let us know if it fixes the unit.