Tech Tip: Subaru Impreza With DTCs P0705, P0851, P2746, P2750 And/Or No Crank, No Start
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Tech Tip: Subaru Impreza With DTCs P0705, P0851, P2746, P2750 And/Or No Crank, No Start

If you receive a customer concern of a Check Engine light, AT Temp light or a no engine crank condition, the wiring harnesses to the transmission range sensor (inhibitor switch) should be closely inspected for damage or a short circuit to the CVT transmission case.

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figure 1If you receive a customer concern of a Check Engine light, AT Temp light or a no engine crank condition, the wiring harnesses to the transmission range sensor (inhibitor switch) should be closely inspected for damage or a short circuit to the CVT transmission case.

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In addition, Slow-Blow Fuse (SBF)-6 in the Main Fuse Box (M/B) may also have failed.

The new-style inhibitor harness assembly was incorporated into CVT production starting with transmission #048056 in the
following vehicles.

Model    VIN
4-Door     C*025294
5-Door     C*233297   

Harness Assembly Inhibitor: New Part #: 31911AA041; Old Part #: 31911AA040

figure 2Service Procedure

1. If any of the above DTCs are stored in memory, inspect the harnesses closely for damage or chaffing in the areas shown in Figure 1.

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If no harness damage is found, diagnose each DTC per the appropriate service manual.

2. If DTC P2746 or P2750 are stored in memory at the same time, the freeze-frame data shows vehicle speed (VSP) to be “0” and the service manual troubleshooting results do not indicate a current fault is present, check to see if the inhibitor switch wiring harness is out of position as shown in Figure 2.

Another possible cause is application of the accelerator before full engagement of the CVT is complete. This can occur when shifting between N and D, N and R or P and R combined with an extended pause between selecting of these ranges and might be confirmed during a road test with the customer. Figure 3

TCM reprogramming will be available in the future for this condition but until then, suggest avoiding the described driving pattern.

3. If DTC P2746 and P2750 are stored in memory at the same time, review with the customer and try to determine exactly when the CEL illuminated.

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Ask if there were any driveability issues or operational concerns with the CVT, such as unusual shift shock or possibly a harsh engagement when shifting into gear.

If you are not familiar with normal CVT operating characteristics it is recommended you compare with a like vehicle before proceeding.

If you confirm a driveability concern as described and ruled out any normal CVT characteristics, there may be a concern with the control valve body. In this case, replace it and then perform the Learning Control procedure to complete the repair.

Any damaged wiring harness must be replaced following the procedures listed in the service manual and routed as shown in Figure 3.

If the casting reinforcement bars of the transmission case are found to have sharp edges, carefully smooth them using a file prior to installation of the replacement harness.

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The revised harness and retaining clip position has been incorporated into production and replacement parts to provide additional clearance between the protective outer covering and the transmission case.

Courtesy of Identifix.

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