Riviera V6-3.8L SC VIN 1 (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:
Ignition "OFF" for at least 10 seconds.
Disconnect the negative battery cable for 30 seconds.
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. To check for an oversize terminal, use a #62 drill bit (shank of drill bit must first be
measured to ensure proper diameter of 0.965 mm (0.038 in.). Place a flag made of tape 1/2 inch up from the bottom of the shank of the drill bit.
Remove connector from PCM and while holding connector up vertically, place the #62 drill bit into the suspect terminal (do not push on drill bit.)
Replace any terminal allowing the drill bit to fall unassisted to the flag of the drill bit.
The PROM 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 "Quad-Drivers."
A shorted solenoid, relay coil, or harness will not damage the PCM but will cause the solenoid or relay to become inoperative.
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 PROM 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 PROM.
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.
An incorrect or faulty PROM, which is installed in the PCM, may set DTC P1623.