TT-16-014

General - DTC P20B2 Coolant Cutoff Valve diagnostic - 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 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 follow the prompts to complete the reset. After performing the SCR reset, clear DTC and then read out DTC's 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 cut off 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 sensord 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.