Code
P1640
DAEWOO
P — Powertrain
Vi motor coil 1 open/short
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UK: 19
EN: 29
RU: 37
AI status
Completed
Completed
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Causes
- Open or short in the VI motor coil winding (internal motor failure)
- Broken, corroded or disconnected connector/pins at the VI motor
- Damaged wiring harness (chafing, pinched, melted insulation) causing open or short to ground/power
- Failed VI motor (stuck or mechanically seized)
- Blown fuse or faulty relay supplying the VI motor circuit
- Faulty ECM/ECU output driver (internal transistor short or open)
Symptoms
- Check Engine MIL illuminated (DTC P1640 stored)
- Reduced or no operation of the variable intake system (loss of intended intake tuning)
- Reduced engine performance or torque in affected RPM range
- Hesitation or slight roughness under load when intake tuning would normally change
- Audible clicking or no movement from actuator when commanded
- Possible limp-home behavior if the ECM limits functions
What to check
- Read and record freeze frame and related stored codes; clear codes and attempt to re-create
- Visual inspection of VI actuator, connector and wiring for damage, corrosion, or contamination
- Check fuses and relays that supply the VI motor circuit
- Back-probe actuator connector to verify supply voltage (battery) and control signal while commanding the actuator with a scan tool
- Measure coil resistance across the VI motor coil pins (compare to spec or check for open/infinite or near-short values)
- Check continuity to ECM connector and for short to ground or battery with harness disconnected
Signal parameters
- Supply voltage: ~12 V battery on the feed/power pin with ignition ON (exact pin varies by vehicle)
- Control signal: switched/driver output from ECM (may be ground-side switching or PWM); when commanded you should see the control pin toggle between near 0 V and higher voltage
- Typical coil DC resistance (typical small actuator coils): commonly in the low ohms to tens of ohms range — check service manual for exact spec; open = infinite Ω, short = near 0 Ω
- Expected current: actuator motors draw moderate current when moving (hundreds of mA to a few amps) — significant deviation suggests fault
- No erratic intermittent signal when actuator is commanded; waveform should be consistent and repeatable
Diagnostic algorithm
- Retrieve all stored codes and freeze-frame data. Note any related intake or actuator codes.
- Visually inspect the VI motor, linkage, connector and harness for damage, corrosion, or water intrusion. Repair any obvious wiring issues.
- Verify relevant fuses/relays are intact and supplying power to the actuator circuit.
- With ignition ON (engine OFF) back-probe the actuator connector: verify battery voltage on the power feed pin and check the control pin while commanding the actuator using a scan tool.
- Measure DC resistance of the VI motor coil (with connector disconnected). If resistance is open (OL) or near short (very low ohms), replace the actuator.
- Check for continuity between the actuator connector and the ECM connector for the control and power circuits. Also check for short to ground or battery on control wires.
- If wiring and actuator appear OK but control signal is absent or stuck, use an oscilloscope or multimeter to verify ECM driver output waveform while commanding the actuator. If the ECM output is defective, consider ECM testing or replacement per manufacturer procedure.
- If diagnosis is inconclusive, substitute a known-good VI actuator (if available) or temporarily repair wiring to confirm before replacing ECM.
- After repairs, clear codes and road-test to confirm the code does not return and that intake function and drivability are restored.
Likely causes
- Connector corrosion or loose terminal at the VI motor
- Open wire or broken conductor in the harness between ECM and VI motor
- VI motor internal coil open or short after contamination or overheating
- ECM driver stage failure (less common than wiring/actuator faults)
Fault status
Status
P1640 — VI motor coil 1 open/short detected. ECM reports open or short circuit in variable intake actuator coil #1; check actuator, wiring, connectors and ECM driver.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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