GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The PCM has two internal processors the E and the T side. They are connected together and share data on an interconnect called the SPI. The ECM sends sensor data to the TCM. This sensor data is checked and if the difference in readings between the two processors is too great, DTC P0606 will set.

Conditions for Setting the DTC

Test Conditions

    •  Valid SPI data is being received.
    •  Ignition voltage is greater than 10 volts.
    •  Ignition on for 5 seconds.

Failure Condition

MAP, ECT or TPS data varies between ECM and TCM.

Action Taken When the DTC Sets

    •  The PCM will illuminate the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
    •  The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records.

Conditions for Clearing the MIL/DTC

    •  The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail.
    •  A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.
    •  A History DTC will clear after forty consecutive warm-up cycles with no failures of any emission related diagnostic test.
    • Use a scan tool to clear DTCs.
    • Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

  1. This DTC indicates an internal PCM problem.

Step

Action

Value(s)

Yes

No

1

Was the On-Board Diagnostic (OBD) System Check performed?

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Go to Step 2

Go to A Powertrain On Board Diagnostic (OBD) System Check

2

Replace the PCM. Refer to PCM Replacement/Programming .

Is the repair complete?

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Go to Powertrain Control Module Diagnosis for Verify Repair

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