- How to Use This Section

ON-BOARD DIAGN0STICS (0BD) SYSTEM CHECK

This should be the starting point of any driveability or symptom diagnosis. Perform the OBD system check, This check verifies the integrity of the powertrain control module (PCM) and its self-diagnostic capabilities. If diagnostic trouble codes (DTCs) are stored, go directly to the numbered DTC chart. Testing and Inspection


VERIFY COMPLAINT

Verify the customer complaint and locate the correct symptom definition. Check all of the items associated with that symptom in both the complaint/condition charts and symptom tables.

Testing and Inspection

GATHER INFORMATION

Gather information from all resources available to pinpoint the "when," "where," "why," and "how" of the symptom road test with the customer when possible to completely understand the symptom. Compare the symptom to a similar vehicle to verify this is an abnormal condition. Find out (when applicable) grade of fuel and where purchased, maintenance history (oil changes, etc.), typical driving cycle, etc. Perform a bulletin search focusing on specific symptoms.

VISUAL INSPECTION

The importance of the visual inspection cannot be overstressed. Visual inspection can lead to correcting a problem without further testing and can save valuable time. The check should include:


^ Use of aftermarket equipment (e.g., alarm systems, cellular phones, lighting, CB radio, etc.):


^ Use of aftermarket parts( e.g., air filter, PCV valve, spark plugs and wires, fuel filter, battery, etc.).


^ Inspect wiring harnesses for proper routing, connections, pinches, chaffing and cuts.


^ Inspect PCM and oxygen sensor grounds for tightness and evidence of corrosion.

CUSTOMER "SNAP-SHOT" FUNCTION

The PCM has the capability of running a "CUSTOMER SNAP-SHOT" function to aid in intermittent diagnosis. In the past, intermittent driveability concerns relied solely on the self-diagnostic capabilities of the on-board diagnostics. With this feature, the customer has the ability to capture engine general information parameters when experiencing drive ability concerns to aid in diagnosis. If the vehicle is equipped with cruise control, activation of the function is accomplished simply by toggling the ON/OFF cruise control switch three times within three seconds. The PCM looks for three transitions either Off or On within the three second window to capture the data. The PCM then sets a diagnostic trouble code P1624 and information is stored in Malfunction History. The Malfunction History can be accessed using a Scan tool. The PCM will allow only one captive per ignition cycle. Tools and Equipment