Caprice V8-265 4.3L VIN W MFI (1995)
Engine Control Module: Component Tests and General Diagnostics
To display diagnostic trouble codes, use a Tech 1 (or equivalent scanner). Grounding the DLC will NOT flash Diagnostic Trouble Code(s) (DTC), but
will enable most outputs when the ignition is "ON" engine "OFF." Grounding the Data Link Connector (DLC) while the engine is running will cause the
Malfunction Indicator Lamp (MIL) to flash to indicate "Open" or "Closed Loop. This is referred to as Field Service Mode."
To clear the DTCs from memory use the Tech 1 or:
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ignition "OFF."
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Disconnect the # 2 fuse (located in the underhood electrical center) for 30 seconds.
Since the Powertrain Control Module (PCM) can have a failure which may affect only one circuit, following the diagnostic procedures in this section
will determine which circuit has a problem and where it is.
If a diagnostic chart indicates that the PCM connections or PCM is the cause of a problem and the PCM is replaced the Knock Sensor (KS) module must
be transferred to the new PCM and the new PCM must then be programmed. If this does not correct the problem, one of the following may be the reason:
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There is a problem with the PCM terminal connections. The diagnostic chart will say PCM connections or PCM. The terminals may have to be
removed from the connector in order to check them properly.
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The problem is intermittent. This means that the problem is not present at the time the system is being checked. In this case. Refer to Diagnosis by
Symptom and make a careful physical inspection of all portions of the system involved.
^ Shorted solenoid, relay coil, or harness. Solenoids and relays are turned "ON" and "OFF" by the PCM using internal electronic switches called
"drivers."
A shorted solenoid, relay coil, or PCM harness will not damage the PCM but will cause the component to be inoperative.
J 34636 or BT-8405 testers or equivalent provide a fast accurate means of checking for a shorted coil or a short to battery voltage.
