Diagnostic Quick Test Description

The Diagnostic Quick Test is a check of system electronics which utilizes the Powertrain Control Module (PCM) to perform diagnostics on itself and its circuitry. This PCM capability is referred to as Diagnostic Test Mode. Since little effort is required to initiate Diagnostic Test Mode, but in return vital information is retrieved quickly, this procedure is referred to as Diagnostic Quick Test.

Although Diagnostic Quick Test appears to be a fast and powerful diagnostic aid, it unfortunately cannot detect all possible failures that can occur within the electronic engine control systems. Therefore, the Diagnostic Quick Test procedures have been carefully constructed to guide and refer you to pinpoint tests that inspect components and circuitry associated with particular symptoms.

Keep in mind that all things that went wrong with vehicles before the age of electronics reached the automobile can still go wrong, and are still the cause of the majority of the driveability problems. That's why the best diagnosis starts with a list of symptoms and possible causes, followed by a careful checking of those causes in the most probable order.

Diagnostic Quick Test is divided into three specialized tests, Key ON Engine OFF (KOEO) Self-Test, Key ON Engine Running (KOER) Self-Test and Continuous Memory Self-Test.

Diagnostic Quick Test checks the integrity and function of the OBD II powertrain control system and outputs the test results upon demand. Diagnostic Quick Test also provides a quick end check of the powertrain control system and is usually performed at the start of each diagnostic procedure. It is also performed at the end of most pinpoint tests for verification of repair and to make sure no other faults existed or were incurred while servicing a previous fault.

A system pass occurs when Diagnostic Quick Test is performed and no Diagnostic Trouble Codes (DTCs) are output and a scan tool communication problem does not exist. System pass means that inputs and outputs that are monitored by the PCM are functioning within normal operating limits. If retrieving Continuous Memory DTCs that are emission related (that light the malfunction indicator lamp [MIL]) and DTCs are not output, then only the emission system has passed. It is still possible that a fault exists in other PCM inputs and outputs.

KEY ON ENGINE OFF SELF-TEST
Key ON Engine OFF (KOEO) Self-Test is a functional test of the powertrain control system performed on demand with the key ON and engine OFF. A fault has to 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 to be retrieved by a scan tool.

KEY ON ENGINE RUNNING SELF-TEST
Key ON Engine Running (KOER) Self-Test is a functional test of the powertrain control system performed on demand with the engine running and vehicle stopped. A fault has to be present at the time of testing for the KOER Self-Test to detect the fault. When a fault is detected, a Diagnostic Trouble Code (DTC) will be output on the data link to be retrieved by a scan tool.

CONTINUOUS MEMORY DTC ACCESS
Continuous memory DTC access is also a self-test of the powertrain control system. Unlike the KOEO and KOER Self-Tests, which can only be activated on demand, the Continuous Self-Test is always active. The test consists of all the OBD II monitors, and the Comprehensive Component Monitor, and is designed to detect failures contributing to driveability or emission concerns. When this test detects a fault, a Diagnostic Trouble Code (DTC) will be stored in PCM memory. The DTC can be retrieved at a later time even if the fault no longer exists. This capability makes Continuous Self-Test valuable when diagnosing intermittent faults.

As part of Diagnostic Quick Test, the technician retrieves DTCs that have been stored in Continuous Memory. During pinpoint testing, the technician may perform a specific drive cycle before running Diagnostic Quick Test. This is necessary to detect certain faults not tested during KOEO or KOER Self-Tests. Under the generic OBD II functions menu, only the Malfunction Indicator Lamp (MIL) DTCs are output. Under the Rotunda(r) New Generation STAR (NGS) Diagnostic Data Link menu, all Continuous Memory DTCs (MIL and non-MIL) are output. MIL DTCs activate the "Check Engine" light in the instrument panel and are only generated for faults dealing with the emission controls. Generally, non-MIL DTCs are for controls other than the emission system on the vehicle.

Any scan tool that meets OBD II requirements can access Continuous Memory to retrieve MIL DTCs. However, when performing KOEO or KOER Self-Test or retrieving all Continuous DTCs, (MIL and non-MIL) with a generic scan tool, it will take additional manually entered commands. All self-tests are menu driven in the New Generation STAR (NGS) scan tool.

During most diagnostic procedures it is required that all DTCs be retrieved. It is necessary to use either the NGS Diagnostic Data Link Menu or the enhanced diagnostic mode in the generic scan tool.

SWITCH MONITOR TEST
The Switch Monitor Test uses the Parameter Identification (PID) monitoring function of the NGS to observe certain inputs to the powertrain control module. The monitored switches will not set DTCs, thus they are manually tested for faults.