DIAGNOSTIC MANUAL
10.8. GRAPH 8: LOW EXHAUST GAS TEMPERATURES (RESTRICTED AFI)
1. Diesel Oxidation Catalyst Outlet
Temperature (DOCOT) (degrees
Fahrenheit) [Red]
2. Diesel Oxidation Catalyst (DOC)
at operating temperature and
stabilized.
3. Diesel Particulate Filter Outlet
Temperature (DPFOT) (degrees
Fahrenheit) [Purple]
4. Diesel Oxidation Catalyst Inlet
Temperature (DOCIT) (degrees
Fahrenheit) [Green]
5. Diesel Particulate Filter (DPF) soot
load (percent) [Blue]
Figure 33
Graph 8: Low Exhaust Gas Temperatures (Restricted AFI)
Graph Analysis:
This graph shows low exhaust gas temperatures indicating a restricted Aftertreatment Fuel Injector (AFI). Low
temperatures in the exhaust stream occur when Diesel Oxidation Catalyst Outlet Temperature (DOCOT) and
Diesel Particulate Filter Outlet Temperature (DPFOT) are less than 900°F (482°C) after the DOC has reached
operating temperature and stabilized (see callout 2, graph 8). This is caused by restricted fuel flow from the
AFI, resulting in less fuel burning in the exhaust stream. This test does not give pass or fail results. It only
allows the user to validate operation of the aftertreatment system by monitoring exhaust gas temperatures.
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