What Does P1668 Mean?
The PCM has detected an abnormally high voltage signal on an output circuit check line. This indicates a short to voltage or internal PCM driver circuit fault affecting one of the controlled outputs.
Common Causes
35%
Short to battery voltage in output circuit wiring harness
30%
PCM internal output driver circuit failure or transistor short
20%
Faulty relay or solenoid with internal short to power
10%
Damaged or pinched wiring causing intermittent short to power supply
5%
Water intrusion or corrosion in connector causing cross-circuit short
Diagnostic Steps
1
Step 1: Disconnect suspected output device (relay/solenoid) and clear codes, retest to isolate fault location
2
Step 2: Measure voltage on output circuit with device disconnected and key on, should read near zero volts
3
Step 3: Inspect wiring harness for damage, chafing, or pinch points where wire may contact power sources
4
Step 4: Check for aftermarket accessories or modifications that may have tapped into PCM-controlled circuits
5
Step 5: Test PCM output driver by measuring resistance to ground with PCM disconnected
Estimated Repair Cost
$150 - $1,000
Parts + labor, varies by vehicle and location
The PCM has detected an abnormally high voltage signal on an output circuit check line. This indicates a short to voltage or internal PCM driver circuit fault affecting one of the controlled outputs.
The most common cause of P1668 (Output Circuit Check Signal High) is: Short to battery voltage in output circuit wiring harness
Typical repair costs for P1668 range from $150 to $1,000, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Depending on affected circuit, may cause various system malfunctions. Generally safe to drive but should be diagnosed promptly to prevent further damage.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1668 to identify the root cause.
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Quick Info
Category
Powertrain
System
Electronic Control System
Difficulty
Type
Manufacturer
Recommended Tools
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