Skip Shift Solenoid Control Circuit Malfunction (Chevrolet)
What does P1664 mean?
The P1664 code means the vehicle's onboard diagnostic system has detected: Skip Shift Solenoid Control Circuit Malfunction (Chevrolet). This is a low severity code.
Common Symptoms
- Skip shift (1-4 shift) not working
- Check Engine Light on
- Forced 1-4 upshift at light throttle
- Skip shift indicator light malfunction
- No noticeable drivability issues
Probable Causes (Ranked by Likelihood)
- Faulty skip shift solenoid Very High
- Open or shorted wiring to skip shift solenoid High
- Blown skip shift fuse Moderate
- PCM skip shift driver failure Low
Step-by-Step Diagnostic Procedure
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Check the skip shift fuse in the under-hood fuse box.
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Locate the skip shift solenoid on the transmission (driver side, near the shift linkage).
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Measure solenoid resistance (typically 20-40 ohms). Replace if open or shorted.
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Check for 12V supply to the solenoid connector with ignition on.
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If the solenoid and wiring test good, command the solenoid on with a scan tool to verify PCM driver function.
Frequently Asked Questions
What is the skip shift feature?
GM's skip shift (CAGS) forces a 1-to-4 upshift at light throttle and low RPM to improve fuel economy. Many owners install a skip shift eliminator to bypass it.
Can I install a skip shift eliminator?
Yes. A simple inline resistor plugs into the solenoid connector and prevents the forced 1-4 shift without setting a code.
Will this affect my transmission?
No. The skip shift solenoid only blocks the shift gate mechanically. It does not affect transmission operation or longevity.