ISB6.7 & ISL9 CM2350 Exhaust Gas Temperature Sensor Failure due to Frequency Desynchronization

1. 2
Aftertreatment Temperature Sensor Out of Range High Failure
Starting in Summer 2015, lots of truck are seeing Check
Engineer Light due to out of range high temperature in the
aftertreatment. After the aftertreatment was checked to be
clean, the sensor was identified as the assignable cause. But
supplier claimed that the sensor is good, while the false
reading was caused by the high noise in the sensor supply
circuit.
To verify, I installed a picoscope and a breakout harness to the
supply circuit to measure the voltage noise. I also created a
screen file for data logger to transfer Cummins Fault Code to
Supplier Fault Code, which is more accurate.
During the test drive, abnormal temperature jump and an ASIC
failure was captured by the data logger. But the supply voltage
stayed in range when the failure happened. The ASIC failure
was later confirmed by the supplier after tearing down the
sensor.
Cummins Fault Code Supplier Fault Code
EGTS_DOC_IN_OOR_HI_ERR TC1 Short to Vbat 00001 FMI=1
TC1 Open Circuit 00101 FMI=5
EGTS_PFS_TC1_ASIC_ERR TC1 ASIC 00110 FMI=6
EGTS_DOC_OUT_OOR_HI_ERR TC2 Short to Vbat 00001 FMI=1
TC2 Open Circuit 00101 FMI=5
EGTS_PFS_TC2_ASIC_ERR TC2 ASIC 00110 FMI=6
EGTS_DPF_OUT_ OOR_HI_ERR TC3 Short to Vbat 00001 FMI=1
TC3 Open Circuit 00101 FMI=5
EGTS_PFS_TC3_ASIC_ERR TC3 ASIC 00110 FMI=6
FC3314 - Aftertreatment DOC Intake
Temperature Sensor Circuit - Voltage
Above Normal or Shorted to High
Source
FC3317 - Aftertreatment DPF Intake
Temperature Sensor Circuit - Voltage
Above Normal or Shorted to High
Source
FC3319 - Aftertreatment Diesel
Particulate Filter Outlet Temperature
Sensor Circuit - Voltage Above Normal
or Shorted to High Source
Diesel Particulate Filter (DPF)
Failure happened between bars.
Supply Voltage stayed in range.
1758C
FMI=6 ASIC Failure