PCM CANNOT COMMUNICATE WITH PDT OR SSS (CYCLE IGN. ON/OFF). Saturn Saturn 1993

For 1990-2009 cars

# PCM CANNOT COMMUNICATE WITH PDT OR SSS (CYCLE IGN. ON/OFF)

#### SUBJECT: PCM Cannot Communicate with PDT or Saturn Service Stall System (Cycle Ignition On/Off)

Due to revisions in the affected model years, with the addition of 1995 Saturns, this bulletin supersedes bulletin 92-T-47A, which should be discarded.

#### MODELS AFFECTED: 1991 - 1995 Saturns

CONDITION: A serial communication interface (SCI) failure causing no powertrain control module (PCM) communication with portable diagnostic tool (PDT) and Service Stall System (SSS). With a SCI failure, the PDT or SSS cannot establish communication with the PCM, however, the vehicle's operation is normal.

CAUSE: In order for the PDT to communicate with the PCM, the PCM must issue a polling message. During certain communication modes, the PCM does not receive all of the information required to issue the poll message and will continue to wait for further data, causing a communication problem.

CORRECTION: Turn the ignition off, wait 10 seconds to reset the PCM and then start the vehicle.

#### NOTE: If engine coolant temperature is 42 degrees Celsius (106 degrees Fahrenheit) or above, it may take up to five minutes of ignition off time to reset the PCM. If the PCM will not communicate after the ignition is cycled, refer to the "Diagnostic IV" chart in the "Electronic Engine Controls Service Manual."

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