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P0662Intake Manifold Tuning Valve Control Circuit High (Bank 1)

The Bank 1 intake manifold tuning valve control circuit is stuck at a high voltage, typically from a short to battery voltage or an open ground path.

Definition

The PCM monitors the voltage on the Bank 1 intake manifold tuning (IMT) valve control circuit and sets P0662 when it reads high when it should be pulled low — pointing to a short to voltage, an open in the low-side path, or a failed driver. The tuning valve stops responding and stays in its default position, so intake runner tuning is fixed and the engine loses some torque at either the low or high end of the RPM range. The MIL illuminates, causing an emissions-inspection failure, but the engine remains safe to drive.

Common causes

  • Control wire shorted to a battery or ignition voltage feed in the harness
  • Open circuit in the valve's ground-side (driver) path reading as pull-up voltage
  • Corroded connector terminal creating high resistance in the control path
  • Melted harness section near the exhaust or EGR bridging circuits
  • Failed PCM low-side driver unable to pull the circuit down

Common misdiagnoses

  • Tuning valve replaced when the harness is shorted to voltage
  • Intake manifold replaced for what is an electrical fault
  • PCM replaced without isolating the harness first
  • Alternator suspected due to the 'circuit high' description

Troubleshooting steps

  1. 1.Confirm the high reading

    Backprobe the control circuit and command the valve; a circuit pinned at battery voltage even when commanded on indicates it cannot be pulled low.

  2. 2.Determine short versus open

    Disconnect the PCM: if the circuit still shows voltage, it is shorted to a power feed; if voltage disappears, the PCM driver or its connection is the fault.

  3. 3.Inspect harness routing

    Trace the control wire for chafes against power feeds, heat damage near the exhaust side, and previous repair splices.

  4. 4.Verify valve and connector integrity

    Check the valve winding resistance against spec and inspect both connector halves for corrosion or spread terminals adding resistance.

  5. 5.Repair and validate switching

    After repair, confirm the circuit toggles correctly with scan-tool commands and the code stays clear through a full warm-up and RPM sweep.

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