Cutlass Ciera L4-2.2L VIN 4 (1995)
Powertrain Control Module: Component Tests and General Diagnostics
To read trouble Diagnostic Trouble Code (DTC)(s), use a Tech 1 scan tool.
To clear DTCs from memory:
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Ignition "OFF" for at least 10 seconds.
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Disconnect the negative battery cable for 30 seconds.
OR
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Use Tech 1 scan tool.
Since the Powertrain Control Module (PCM) can have a fault 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 the PCM connections or PCM is the cause of a problem, and the PCM is replaced, but does not correct the problem, one of
the following may be the reason:
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.
The PCM or EPROM is not correct for the application.
The incorrect components may cause a malfunction and may or may not set a DTC.
The problem is intermittent.
This means 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." Each driver is part of a group of
four called a "Quad-Driver Module" (QDM). Most of the drivers switch the ground side of a solenoid or relay circuit which is fed by a connection
to battery voltage. A shorted or low resistance solenoid or relay, or a shorted harness can allow too much current to flow through a QDM. This will
not permanently damage a PCM, as the QDM will limit current. However, a circuit which tends to allow too much current into the QDM will
probably cause the solenoid or relay to become inoperative, and should set a DTC 27 or 28.
J 34636 or ET 805 testers provide a fast, accurate means of checking for a shorted solenoid, relay coil or a short to battery voltage.
The EPROM may be faulty.
Although these rarely fail, it operates as part of the PCM. Therefore, it could be the cause of the problem. Substitute a known good EPROM.
The replacement PCM may be faulty.
After the PCM is replaced, the system should be re-checked for proper operation. If the diagnostic chart again indicates the PCM is the problem,
substitute a known good PCM. Although this is a rare condition, it could happen.
