What this code means

The PCM detected a voltage difference exceeding the maximum allowable threshold between the two circuits that supply it with battery voltage. This code is commonly caused by a failing ignition switch, which is a known issue on Trailblazer, Envoy, and SSR models among others.

Symptoms

• Check Engine Light
• Intermittent stalling
• Reduced Engine Power message
• Multiple warning lights
• Electrical accessories cutting out
• Intermittent no-start

Common causes

• Failed or failing ignition switch (most common)
• Defective fuse or fuse box
• Loose PCM power connector
• Corroded ignition switch connector
• Damaged wiring in ignition circuit

Diagnostic steps

1. Test voltage at both PCM power supply circuits
2. Compare voltage between the two circuits
3. Inspect ignition switch connector
4. Test ignition switch output under load
5. Check all related fuses

Repair notes

Replace ignition switch (most common fix). Check fuses and connectors. This is a known issue on many GM trucks and SUVs, particularly Trailblazer, Envoy, and SSR.

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