P1351

Code

CHEVROLET P — Powertrain

IC Circuit High Voltage

Brand: CHEVROLET

Type: P — Powertrain

Views: UK: 38 EN: 71 RU: 65

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Page language: EN

Causes

Short to battery voltage on the IC/ignition driver circuit
Open or high-resistance ground for the ignition coil/ignition control module
Failed ignition coil or ignition control (IC) module
Faulty PCM/ECM driver transistor
Corroded, damaged, or loose connector/pin at coil/module or PCM
Aftermarket ignition components or incorrect parts/installation

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Engine misfire(s) or rough idle
Reduced engine power or hesitation
Hard start or no-start in severe cases
Increased fuel consumption and emissions

What to check

Retrieve freeze frame and stored codes with a scan tool; note affected cylinder(s) and conditions
Visual inspection of coil packs, wiring harness, and connectors for damage, corrosion, or loose pins
Check battery voltage and main fuses/ignition fuses
Scan live data for coil driver status, misfire counters, and engine RPM
Perform a resistance/continuity check from the coil IC pin to the PCM pin and to ground
Use a lab scope to inspect ignition driver waveform where possible

Signal parameters

Expected: IC driver circuit toggles between ~battery voltage (inactive) and near 0 V (when driver grounds the coil primary) depending on driver type
Normal idle switching frequency: varies with RPM; dwell/duty changes with engine speed and PCM strategy
Fault trigger: sustained voltage higher than expected on the IC control line (e.g., voltage near battery when it should be pulled low) or intermittent voltage spikes above battery
Typical nominal values: battery voltage ≈ 11.5–14.5 V, coil primary when driven ≈ 0–1 V to ground; open/short conditions will deviate significantly

Diagnostic algorithm

Confirm the code and capture freeze frame data with scan tool. Note engine conditions (RPM, load, temp).
Visually inspect ignition coils, connectors, wiring routes, and PCM connector for damage, corrosion, or aftermarket splices.
Check battery voltage and fuses. Repair any low-voltage or blown-fuse issues first.
Back-probe the IC control wire at the coil/module with a DVOM: observe voltage with ignition ON and during cranking. Look for unexpected high or steady battery voltage when the driver should pull low.
Measure continuity and resistance between coil/module control pin and the PCM control pin; check for shorts to B+ and to ground. Repair wiring faults as needed.
If available, use an oscilloscope to view the driver waveform while cranking/running to verify switching behavior and to spot spikes or lack of switching.
Swap suspected faulty coil/module with a known-good unit (if serviceable and identical) and re-test to see if the code follows the component.
If wiring and coils check good, test PCM driver output; consult service manual for PCM bench tests. Replace PCM only after confirming driver failure.
Clear codes and perform a road test to verify repair. Monitor for reappearance and check for related misfire codes.

Likely causes

Pinched/shorted harness where IC trigger wire contacts B+
Ignition coil/module internal short or leakage to B+
Missing/poor ground at coil pack bracket or engine block
Damaged connector terminal sending battery voltage to PCM input
PCM driver failure after repeated overstress

Fault status

⚠️ Status

PCM detected excessive/high voltage on the IC (ignition control) circuit. Fault indicates abnormal voltage level on ignition driver circuit — check wiring, coil/module, and PCM driver.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours

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P1351 — IC Circuit High Voltage