Subaru Tech Tip: Harsh AWD Engagement/Code 45 Set – UnderhoodService
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Subaru Tech Tip: Harsh AWD Engagement/Code 45 Set

If you encounter a TCU Code 45 (intake manifold pressure signal) on any 1999-2002 4EAT Subaru vehicle, and have confirmed the wiring and connectors as outlined in the appropriate service manual, it will be necessary to replace the TCU with one listed in TSB 16-66-02.

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If you encounter a TCU Code 45 (intake manifold pressure signal) on any 1999-2002 4EAT Subaru vehicle, and have confirmed the wiring and connectors as outlined in the appropriate service manual, it will be necessary to replace the TCU with one listed in TSB 16-66-02. Note that if the same vehicle is experiencing an ECM code for the pressure signal, replacement of the TCU will not correct it. You will need to diagnose and repair it according to the service manual.

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These new TCUs also include a slight logic change to address AWD harsh engagement. Some customers may comment that when they are driving in snow and ice, and they try to accelerate during slow-speed driving, they feel a bang from the rear of the vehicle. This is caused by the transfer clutch being applied quickly when the system detects slight wheel slippage. You should confirm the AWD is working properly prior to replacing the TCU.

Note: These logic changes were incorporated into production from the start of the 2003 model year.

Technical service bulletin courtesy of ALLDATA.

For additional information, visit www.alldata.com.

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