Colorado 2WD L5-3.5L VIN 6 (2005)
then powering down the PCM. The definition of a trip depends upon the diagnostic. Some diagnostic tests run only once per trip (i.e., catalyst
monitor) while other tests run continuously during each trip (i.e. misfire).
WARM-UP CYCLE
The PCM uses warm-up cycles to run some diagnostics and to clear any DTCs. A warm-up cycle occurs when the engine coolant temperature
increases 22°C (40°F) from the start-up temperature. The engine coolant must also achieve a minimum temperature of 71°C (160°F). The PCM
counts the number of warm-up cycles in order to clear the MIL. The PCM will clear the DTCs when 40 consecutive warm-up cycles occur without a
malfunction.
DIAGNOSTIC TROUBLE CODES (DTCS)
The PCM is programmed with test routines that test the operation of the various systems the PCM controls. Some tests monitor internal PCM
functions. Many tests are run continuously. Other tests run only under specific conditions, referred to as Conditions for Running the DTC. When the
vehicle is operating within the conditions for running a particular test, the PCM monitors certain parameters and determines if the values are within an
expected range. The parameters and values considered outside the range of normal operation are listed as Conditions for Setting the DTC. When the
Conditions for Setting the DTC occur, the PCM executes the Action Taken When the DTC Sets. Some DTCs alert the driver via the MIL or a
message. Other DTCs do not trigger a driver warning, but are stored in memory. The PCM also saves data and input parameters when most DTCs are
set. This data is stored in the Freeze Frame and/or Failure Records.
The DTCs are categorized by type. The DTC type is determined by the MIL operation and the manner in which the fault data is stored when a
particular DTC fails. In some cases there may be exceptions to this structure. Therefore, when diagnosing the system it is important to read the Action
Taken When the DTC Sets and the Conditions for Clearing the DTC in the supporting text.
There are different types of DTCs and different actions taken when the DTCs set. Refer to Diagnostic Trouble Code (DTC) Type Definitions for a
description of the general characteristics of each DTC type.
DTC STATUS
When the scan tool displays a DTC, the status of the DTC is also displayed. The following DTC statuses are indicated only when they apply to the
DTC that is set.
Fail This Ign. (Fail This Ignition): Indicates that this DTC failed during the present ignition cycle.
Last Test Fail: Indicates that this DTC failed the last time the test ran. The last test may have run during a previous ignition cycle if an A or B type
DTC is displayed. For type C DTCs, the last failure must have occurred during the current ignition cycle to appear as Last Test Fail.
MIL Request: Indicates that this DTC is currently requesting the MIL. This selection will report type B DTCs only when they have requested the
MIL (failed twice).
Test Fail SCC (Test Failed Since Code Clear): Indicates that this DTC that has reported a failure since the last time DTCs were cleared.
History: Indicates that the DTC is stored in the PCM History memory. Type B DTCs will not appear in History until they have requested the MIL
(failed twice). History will be displayed for all type A DTCs and type B DTCs (which have requested the MIL) that have failed within the last 40
warm-up cycles. Type C DTCs that have failed within the last 40 warm-up cycles will also appear in History.
Not Run SCC (Not Run Since Code Clear): DTCs will be listed in this category if the diagnostic has not run since DTCs were last cleared. This
status is not included with the DTC display since the DTC can not be set if the diagnostic has not run. This information is displayed when DTC Info is
requested using the scan tool.
