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DTC P1645 EVAP Solenoid Output Circuit

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  • 3 weeks later...

The PCM contains chips called Output Driver Modules that provide 7 switchable ground outputs for operating solenoids, relays, telltales, and other devices. Each of these ground outputs has an internal fault line that feeds back to the PCMs microprocessor. When the output is OFF, the output driver should receive the 12 volts fed to the solenoid, relay, etc. When the output is ON, it should receive 0 volt since it is grounding the output. If it receives 0 volt when the output is OFF or 12 volts when the output is ON, it sets the fault line low. DTC P1645 is used to monitor the fault line of the EVAP purge solenoid.

Conditions for Setting the DTC

Test Conditions

DTC P1640 not set.

Engine running at least 10 seconds.

Failure Condition

Fault line is low for 2 seconds.

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.

Diagnostic Aids


Do not apply voltage to the EVAP vacuum switch. The voltage supplied by the PCM is of a low current design. The EVAP vacuum switch may be damaged if jumpered to voltage without this current limiting feature.

Use the Failure Rec. to aid in diagnosing an intermittent fault. Use the data captured when the DTC set to determine if an open or shorted condition caused the DTC to set.

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