Initial Inspection and Diagnostic Overview

ON - BOARD DIAGNOSTIC TESTS

On-Board Diagnostic (OBD) Test Description
The scan tool must be connected to the data link connector (DLC) for communication with the vehicle. The DLC is located in the passenger compartment. It is attached to the instrument panel and accessible from the driver's seat.

The DLC is rectangular in design and capable of accommodating up to 16 terminals. The connector has keying features to allow easy connection. The vehicle connector and the test equipment connector have latching features that ensure the test equipment connector will remain mated when properly connected.

The required scan tool functions are described below:
- Monitor, record and playback of PIDs
- Freeze frame PID data
- Diagnostic test modes (self-test) / clear diagnostic DTCs (PCM reset)
- Output test mode
- Reset keep alive memory
- Digital measurement system (multi-meter functionality)
- Diagnostic monitoring test results (for OBD II on-board monitors)
- On board system readiness (OBD II monitor completion status)

See the scan tool manufacturer's manual for specific information on scan tool set-up and operation.

Quick Test

Quick Test is divided into three specialized tests:
- Key On Engine Off (KOEO) on-demand self-test
- Key On Engine Running (KOER) on-demand self-test
- Continuous memory self-test

Quick test checks the integrity and function of the electronic EC system and outputs the test results when requested by a scan tool. Quick test also provides a quick end check of the powertrain control system and is usually performed at the start of each diagnostic procedure with all accessories off. Quick test is also performed at the end of most pinpoint tests for verification of repair and to make sure no other faults were incurred while repairing a previous fault. A system pass will be displayed when no DTCs are output and a scan tool communication error does not exist. System pass means that hardware monitored by the PCM is functioning within normal operating limits. Only a system pass, DTC or an incomplete OBD II drive cycle (P1000) will be displayed.

Key On Engine Off (KOEO) On-Demand Self-Test
Key on engine off (KOEO) on-demand self-test is a functional test of the powertrain control module performed on demand with the key on and the engine off. This test will perform checks on certain sensor and actuator circuits. A fault must be present at the time of testing for the KOEO self-test to detect the fault. When a fault is detected, a diagnostic trouble code (DTC) will be output on the data link at the end of the test when requested by a scan tool.

Key On Engine Running (KOER) On-Demand Self-Test
Key on engine running (KOER) on-demand self-test is a functional test of the PCM performed on demand with the key on engine running and vehicle stopped. A check of certain inputs and outputs is made during operating conditions and at normal temperature. The brake pedal position, transmission control and power steering switch tests are part of KOER on-demand self-test and must be performed during this operation if applicable. These are described below. A fault must be present at the time of testing KOER on-demand self-test to detect the fault. When a fault is detected, a diagnostic trouble code (DTC) will be output on the data link at the end of the test when requested by a scan tool.

Brake Pedal Position Test
This tests the ability of the electronic EC system to detect a change of state in the stoplight switch. Brake pedal must briefly be applied and released on all vehicles equipped with Brake Pedal Position input. This is done during KOER on-demand self-test.

Transmission Control Switch Test
This tests the ability of the Electronic EC system to detect a change of state in the transmission control switch (TCS). Switch must briefly be cycled on all vehicles equipped with TCS input. This is done during the KOER on-demand self-test.

Power Steering Pressure Test
This tests the ability of the electronic EC system to detect a change in power steering system fluid pressure. The steering wheel must briefly be turned at least 1/4 of a revolution on vehicles equipped with a power steering pressure (PSP) switch or sensor. This is done during the KOER on-demand self-test.

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 DTCs 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. See drive cycles for more information. When a fault is stored in memory, a 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 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 start-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 vehicle warm up cycles or a PCM reset.

Any scan tool that meets OBDII requirements can access continuous memory to retrieve emission related MIL DTCs. However, not all scan tools access pending and non emission related (non-MIL) DTCs in the same way.

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

Output Test Mode Procedure
The output test mode (OTM) aids in servicing output actuators associated with the PCM. This mode allows the technician to energize and de-energize most of the system output actuators on command. When entering OTM, the outputs can be turned off and on without activating the fan control. The low and high speed fan controls) may be turned on separately without energizing the other outputs. This function is supported by each vehicle strategy and may not be available on all scan tools.

As a safety precaution, output test mode will default to the off state after 10 minutes and fuel pump off after approximately 7-10 seconds. OTM will also turn off after the vehicle is started or after cycling the key off then on

WARNING:
- Safety must be observed when using output test mode.
- When all outputs are on, the electric fuel pump is briefly energized, make sure the fuel system is intact and is not being serviced at this time.
- When low speed or high speed fan control(s) are turned on, make sure fan blades are clear of any obstruction.
- Failure to follow these instructions may result in personal injury.