Quick Test Or OBD Test -- KOEO & KOER

On-Board Diagnostic (OBD) Test Description
The On-Board Diagnostic (OBD) Test is divided into three special tests: Key On Engine Off Self-Test (KOEO), Key On Engine Running (KOER) Self-Test and Continuous Memory DTCs Self-Test. The OBD test checks the integrity and function of the powertrain control system and outputs the test results when requested by the WDS or equivalent Tester. It also provides a quick end check of the powertrain control system. It is usually performed at the start of each diagnostic procedure with all the accessories off and is performed at the end of most troubleshooting tests for verification of repair and to make sure no other faults were incurred while servicing a previous fault.

System Pass
A system pass will be displayed when no DTCs are output and no WDS or equivalent Tester communication error exists. System pass means that hardware monitored by the PCM is functioning within normal operating limits. When using the WDS or equivalent Tester, all step by step instructions are defined in the WDS or equivalent instruction manual. When using a generic scan tool, KOEO and KOER self-tests may not be supported. Refer to the manufacturer's manual for details.

Key ON, Engine OFF (KOEO) On-Demand Self-Test
Key ON, Engine OFF (KOEO) is a functional test of the PCM performed on demand. A fault must be present at the time of testing for the self-test to detect the fault. This test will perform checks on certain sensor and actuator circuits. A DTC will be output on the data link at the end of the test when requested by the WDS or equivalent Tester. Only system pass, hard fault code or an incomplete OBD II drive mode will be displayed.

Key ON Engine Running (KOER) On-Demand Self-Test
Key On Engine Running (KOER) is a functional test of the PCM performed on demand with the engine running and vehicle stopped. A check of the inputs and outputs is made during operating conditions and at normal temperature. The brake on/off, transmission control and power steering pressure switch tests are part of the KOER self-test and MUST be performed during this operation (see below). A fault must be present at the time of testing to detect the fault. A DTC will be output on the data link at the end of the test when requested by the WDS or equivalent Tester. Only system pass, hard fault code or an incomplete OBD II drive mode will be displayed.

Continuous Memory Self-Test
Testing for Continuous Memory DTCs is a functional test of the powertrain control module performed under any condition (engine running or off) with the key on. Unlike the KOEO and KOER self tests, which can only be activated on demand, the Continuous Self Test is always active. A fault does not need to be present at the time of testing for Continuous DTC's and is therefore, especially valuable when diagnosing intermittent faults. This test will detect failures contributing to driveability or emission concerns. The vehicle may need to be driven or the OBD II Drive Cycle completed to allow the PCM to detect a fault. When a fault is stored in memory, a Diagnostic Trouble Code (DTC) will be output on the data link at the end of the test when requested by a scan tool.

There are two types of Continuous DTCs. The first type is an emission related malfunction indicator lamp (MIL) code which will illuminate the CHECK ENGINE or SERVICE ENGINE SOON indicator in the instrument cluster. The second is a non-emission-related, non-MIL code which will never illuminate the cluster indicator.

For emission-related MIL codes. the PCM will store the DTC in continuous memory when a fault is detected for the first time. At this point the DTC will not illuminate the MIL and is now considered a pending code. The purpose of pending codes is to assist in repair verification by reporting a pending DTC after one drive cycle. If the same fault is detected after the next ignition star-run cycle, the emission-related MIL code will illuminate the MIL. The MIL will remain on even if the fault is intermittent. The MIL will be extinguished if the fault is not present through three consecutive drive cycles or a PCM reset is performed. Also, an emission-related pending MIL and non-emission-related, non-MIL code will be erased after approximately 40 - 80 vehicle warm up cycles or a PCM reset.

Any scan tool that meets OBD II requirements can access Continuous Memory to retrieve emission-related MIL DTCs However, not all scan tools access pending and nonemission-related non-MIL DTCs in the same way. If using the WDS (or equivalent) scan tool, all MIL (including pending) and non-MIL codes are retrieved together on the same screen.

During most diagnostic procedures, it is required that all DTCs be retrieved and cleared. Consult the instruction manual from the tool manufacturer for specific instructions.

Parameter Identification (PID) Access
The PID mode allows access to certain data values, analog and digital inputs and outputs, calculated values and system status information. This includes analog and digital signal inputs and outputs along with calculated values and system status. There are two types of PID lists available. The first is the Generic OBD II PID list. This is a standard set of PIDs for all manufacturers which all scan tools musts be able to access. The second is a Mazda specific list which can be accessed by the WDS or equivalent Tester. When accessing any of these PIDs, the values will be continuously updated. For a complete list of all PIDs, see POWERTRAIN CONTROL MODULE (PCM) INSPECTION.

Brake "On/Off" Test
This tests the ability of the powertrain control system to detect a state of change in the stop lamp switch. The brake pedal MUST briefly be applied and released on all vehicles with brake on/off input. This test is done during the KOER self-test.

Transmission Control (O/D OFF) Switch Test
This tests the ability of the powertrain control system to detect a state of change in the O/D OFF switch. The switch MUST briefly be cycled on all vehicles with the O/D OFF switch. This test is done during the KOER self-test.

Power Steering Pressure (PSP) Switch Test
This tests the ability of the powertrain control system to detect a change in power steering fluid pressure. The steering wheel MUST briefly be turned at least 1/4 of a revolution. This test is done during the KOER self-test.