This bulletin applies to all 2010-later Chevy vehicles equipped with a diesel engine with DPF (diesel particulate filter). The MIL may be on accompanied by excessive tailpipe smoke. DTCs P2002, P226D and/or P244A may be set in the ECM.
P2002 will set if the properly functioning system detects a cracked or broken DPF. The exhaust particulate sensor is used to diagnose this failure. This code is set when the ECM detects that the particulate filter has degraded beyond a calibrated threshold.
P226D will set if the system detects that the DPF is missing. The exhaust pressure differential sensor is used to diagnose this failure. The code sets when the ECM detects that the pressure difference over the DPF is less than a set threshold.
P244A sets if the exhaust pressure differential sensor lines are disconnected or blocked. The code is set when the ECM detects the diesel particulate filter exhaust differential pressure sensor is lower than the minimum threshold.
A properly functioning diesel particulate filter should remove most if not all soot particles from the exhaust stream. The following test should NOT be performed immediately after a regeneration because of the reduced filtration efficiency of the DPF without any soot in it. The purpose of this test is to aid in diagnosing a DPF that has failed internally.
Hold a cheesecloth or equivalent across the tailpipe opening. Have an assistant rev the engine to the rev limiter and back to idle. Repeat this a total of eight times.
A failed test will show excessive soot particulates on the cheesecloth. These soot particles indicate that the exhaust particulate filter is no longer able to capture all of the soot particles and needs to be replaced. A passing test will show no or very minimal signs of soot particles.
