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Home / DTC / P0662 — Intake Manifold Tuning (IMT) Valve Solenoid Control Circuit High Voltage

P0662 — Intake Manifold Tuning (IMT) Valve Solenoid Control Circuit High Voltage

Detailed page for trouble code P0662.

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Code

P0662

HUMMER P — Powertrain

Intake Manifold Tuning (IMT) Valve Solenoid Control Circuit High Voltage

Brand: HUMMER
Type: P — Powertrain
AI status
Completed
ready
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Page language: EN

Causes

  • Open or damaged wiring in IMT solenoid harness
  • Short to battery voltage (B+) on the control wire
  • Corroded or contaminated connector terminals
  • Failed IMT valve solenoid (internal short or internal fault)
  • Faulty PCM driver/output stage
  • Blown or corroded fuse or related power/relay fault

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Possible reduced engine power or limp mode
  • Rough idle or stumble during acceleration
  • Unusual intake/valve noise when IMT should operate
  • Poor drivability under varying load conditions (where IMT affects torque)

What to check

  • Retrieve DTC and freeze-frame data with a scan tool; confirm P0662 and check for related codes
  • Visually inspect IMT solenoid connector, wiring harness, and chassis grounds for damage, corrosion, or pin pushed out
  • Check for aftermarket wiring or recent repairs in the intake harness area
  • Measure voltage at the IMT harness connector with connector disconnected and key ON; note voltage and compare to battery voltage
  • Measure IMT solenoid coil resistance (with connector disconnected) and compare to spec
  • Use a scope or DVOM to observe control waveform while commanding IMT on/off with a scan tool (watch for PWM or expected switching to ground)

Signal parameters

  • Solenoid coil resistance (typical range): ~5–40 Ω (refer to factory spec for exact value)
  • Inactive circuit voltage at solenoid connector (key ON, PCM not commanding): ~battery voltage (~11–14.5 V)
  • Active control: PCM usually switches the solenoid to ground or applies PWM; commanded low-to-ground measured at harness: near 0 V or a PWM waveform with duty proportional to command
  • High-voltage fault condition: voltage higher than expected at the control circuit (unexpected presence of battery voltage on driver output when it should be low, or above PCM threshold)

Diagnostic algorithm

  1. Confirm DTC and capture freeze-frame/live data. Note engine conditions when fault set.
  2. Visual inspection: check connector for corrosion, bent pins, water intrusion, damaged insulation, and secure connector mating.
  3. With ignition OFF, disconnect IMT solenoid. Measure coil resistance between the solenoid terminals and compare to factory spec. If infinite/open or shorted to ground/B+ → replace solenoid.
  4. With harness disconnected, key ON (engine OFF), measure voltage at the PCM side of the connector: one terminal should see battery voltage (supply), the control terminal behavior depends on PCM (often near battery when inactive).
  5. Command IMT ON using a scan tool while probing the control terminal. Expect voltage to be pulled low or see PWM. If control line stays at battery voltage or goes above expected threshold → suspect short to B+ or PCM driver fault.
  6. Check for short to battery: isolate wiring and use an ohmmeter to check for continuity between control wire and battery positive with ignition OFF. If short present, trace and repair harness.
  7. Check ground circuits for continuity and secure chassis grounds related to PCM and intake system.
  8. If wiring and solenoid good but control still shows abnormal high voltage, perform PCM output driver tests per service manual. Replace PCM only after all wiring and component faults are ruled out.
  9. After repair, clear codes and road test. Re-scan to confirm code does not return.

Likely causes

  • Wiring short to battery or fused B+ at the IMT control harness
  • Corroded/loose connector at the IMT solenoid causing abnormal readings
  • Failed IMT solenoid coil with internal short to supply
  • PCM output driver fault after other wiring checks are clean

Fault status

⚠️ Status
PCM detected excessive voltage on the Intake Manifold Tuning (IMT) valve solenoid control circuit. Diagnostic trouble code P0662 stored; MIL on. Further inspection of IMT circuit wiring, connector, solenoid, fuses/relays, and PCM driver required.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-2.5 hours
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