In this Call Of The Week from Ron Ananian, The Car Doctor Radio Show...

Joe from Pennsylvania has a 2010 Chevy Impala that intermittently gets stuck in Park. The shifter doesn’t have a manual release, and AAA refuses to tow it in that condition. Ron explains the issue likely involves the shift interlock circuit, which depends on the brake light switch, Body Control Module (BCM), and a solenoid controlled by a dark green wire with a white stripe.

Ron advises Joe to:

• Check if brake lights work when the issue occurs.

• Test for 12V on the green/white wire when pressing the brake.

• Use a 194 test bulb inline on that wire to confirm power.

• Check the ground at the solenoid.

• Make sure the brake switch was calibrated (BPP calibration) if it was replaced.

If power reaches the solenoid but it doesn’t click, it’s likely the solenoid or ground. If no power, the problem is upstream in the circuit.

Ron emphasizes understanding the circuit before replacing parts.

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