DTC Test Descriptions
The self-diagnostic tests run to determine if a subsystem has passed or failed a specified test. After a test is performed the PCM will record test PASS/FAIL criteria for display with a Scan tool. Each DTC will have 4 records and are as follows:
^ TEST PASSED THIS IGNITION - Indicates whether a diagnostic test has reported a test passed this ignition cycle.
^ TEST FAILED THIS IGNITION CYCLE - If a diagnostic test was performed, and it was determined a fault existed during that ignition cycle, then the status will be indicated.
^ TEST PASSED SINCE CODE CLEAR - Indicates a diagnostic test passed since the last time DTCs were cleared or the battery was disconnected.
^ TEST FAILED SINCE CODE CLEAR - Indicates whether a diagnostic test has reported a fault since the last time DTCs were cleared or the battery was disconnected.
A "PASS" is defined as a key On-Run-key Off cycle in which all the criteria were met for a given diagnostic test to run. During any given drive cycle key On-Run-key Off, criteria may or may not have been met to perform all diagnostic tests. No "PASS" will occur for a given diagnostic until the vehicle is driven in such a manner as to meet all the enable criteria. If a test is desired on a particular subsystem to determine if it "passes" or "fails" refer to the specific DTC for test parameters. The parameters are calibrated conditions the PCM requires in order to perform the test. If a test has not been run, monitor the Scan tool pass/fail DTC status at the time the parameters have been met.
The Scan tool will display whether the DTC in the PCM's memory is active or history. The following describes the active/history criteria for each DTC.
Active - An active DTC indicates that the last time a diagnostic test was performed on a particular system or sub-system it failed. A problem may no longer exist, but since another test has not been run, the fault still appears active. An active status will remain between ignition cycles if a test was not run and did not pass prior to turning Off the ignition.
History - A history DTC indicates there have been enough faults detected to determine a problem exists. Diagnostic trouble codes that are calibrated to turn On the MIL on the first occurrence, and all non-emission codes will be stored in history as soon as a fault becomes active. However a diagnostic DTC that is calibrated to turn on the MIL on the 2nd occurrence (Type B) will become active on one trip and then on the 2nd occurrence of the DTC will be stored in history and the MIL will be illuminated. Regulations require that the MIL be illuminated for three trips, when any emission related diagnostic fault occurs. Therefore, it will take three ignition cycles in a row, with three passing tests, to turn Off the lamp. The indicator provides information to determine which diagnostic is still illuminating the MIL and whether a fault exists or not.
NOTE: If a catalyst damaging misfire occurs and a misfire DTC sets (type A), the MIL lamp will be turned Off after three passed trips.
Lamp Requested - Indicates whether a diagnostic DTC code is requesting the MIL to be illuminated.
It is important to remember that the DTC as well as any stored malfunction history will be erased if the vehicle battery has been disconnected or a clear DTC command is issued to the PCM. DTCs and malfunction history records will also be erased if 40 passes have been recorded without any faults. The emission DTCs (type A or B) will use a separate counter from the non-emission (type C and D) codes.
Warm Up Cycle - A warm-up cycle is defined as engine temperature reaching a minimum of 71°C (160°F) and a rise in temperature of at least 22°C (720°F) over the course of a trip.