Output Circuit Check Signal High (Chevrolet)
What does P1660 mean?
The P1660 code means the vehicle's onboard diagnostic system has detected: Output Circuit Check Signal High (Chevrolet). This is a moderate severity code.
Common Symptoms
- Check Engine Light on
- Malfunction indicator lamp stays on
- Cooling fan running constantly
- Air conditioning compressor not engaging
- Various output circuits malfunctioning
Probable Causes (Ranked by Likelihood)
- Faulty PCM output driver Very High
- Shorted output circuit wiring High
- Failed relay controlled by PCM Moderate
- Poor PCM ground connection Low
Step-by-Step Diagnostic Procedure
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Retrieve freeze frame data to identify which output circuit triggered the code.
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Inspect PCM connectors for corrosion, bent pins, or water damage.
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Test individual output circuits commanded by the PCM using a scan tool bidirectional test.
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Measure resistance of suspected output circuits and compare to specifications.
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Check PCM ground circuits for proper continuity and low resistance (under 0.5 ohms).
Frequently Asked Questions
Does P1660 mean I need a new PCM?
Not necessarily. While a failed PCM output driver is common, shorted wiring or a failed relay can also cause this code. Diagnose the circuit before replacing the PCM.
Can I still drive with this code?
Generally yes, but affected output circuits may not work properly. If the cooling fan or fuel pump circuit is affected, driving could cause overheating or stalling.
Is a PCM replacement expensive?
A new PCM typically costs $400-$800 with programming. However, some shops offer PCM repair services for $150-$300 which can fix output driver failures.