P030F

Code

Generic P — Powertrain

Ignition B Control Signal Circuit High

Brand: Generic

Type: P — Powertrain

Views: UK: 22 EN: 34 RU: 32

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Page language: EN

Causes

Short to battery voltage on the Ignition B control circuit
Open or high-resistance wiring or poor connector connection
Faulty ignition coil or ignition module (igniter) on the B channel
Faulty ECM/PCM ignition driver transistor
Intermittent wiring damage (chafing, corrosion) or water ingress
Incorrect or poor grounding elsewhere in the ignition/engine harness

Symptoms

Check Engine Light illuminated with P030F stored
Misfire on cylinder(s) associated with Ignition B channel or rough idle
Reduced engine power, hesitation, or stalling
Poor fuel economy
Possible no-start or hard-crank condition if driver fails

What to check

Read freeze-frame and live data: note ignition B status and any related misfire counters
Visually inspect coil/igniter B, wiring harness, and connectors for damage, corrosion, or loose terminals
Compare connector terminal voltages and waveforms of Ignition B to another known-good ignition channel
Measure coil primary resistance and secondary resistance per manufacturer spec
Check for shorts to battery (+) and to ground at the coil connector (with key off)
Wiggle the harness and connectors while monitoring voltage/waveform to find intermittent faults

Signal parameters

Design-dependent: many systems are low-side switched. Typical expected: OFF ≈ battery voltage (≈12V), ON (driver active) ≈
If system is high-side switched the reverse applies: ON ≈ battery voltage, OFF ≈ ~0 V. Check service manual for vehicle specifics.
A healthy ignition control waveform is a pulsed signal synchronized to engine speed/ignition events; pulse frequency increases with RPM.
Primary coil resistance typically in the range specified by manufacturer (commonly a few ohms to tens of ohms); compare to known-good channel.
A persistent voltage above the expected ON/OFF threshold (e.g., stuck near battery voltage when it should be low) will set the Circuit High code

Diagnostic algorithm

Safety: disable ignition and disconnect battery if required for component checks, follow vehicle-specific safety procedures.
Clear the code, start engine (or crank as applicable) and confirm P030F returns while monitoring live data.
Visually inspect the Ignition B coil/igniter, connector and wiring for damage, corrosion, burnt pins or melted insulation.
With ignition ON (engine off), backprobing the Ignition B control terminal: measure voltage. Compare to expected value from service manual and to another ignition channel.
With engine cranking or running, use a lab scope to inspect the Ignition B waveform. Look for stuck-high voltage, missing pulses, or abnormal shapes.
Measure primary and secondary coil resistances and compare to spec and to another identical coil. If out of range, replace the coil/igniter.
Check continuity and resistance between the control terminal and the ECM connector; check for short to B+ and short to ground.
If wiring and coil check good, swap coil/igniter B with another channel (if interchangeable) and see if the code or misfire follows the coil.
If fault follows the harness or remains only on the B channel after swap, repair wiring/connector. If fault follows the ECM output, consider ECM replacement only after verifying wiring and loads.
After repairs, clear codes and verify proper operation under all conditions (idle, acceleration, varied RPM).

Likely causes

Short to B+ on the Ignition B control wire (most common when circuit reads high)
Failed coil pack or igniter that ties the control terminal to battery voltage
Connector terminal corrosion, push-out, or bent pin causing high voltage reading
Open/short in harness near coil/igniter or aftermarket wiring damage
ECM ignition driver failure (less common but possible)

Fault status

⚠️ Status

Ignition B control circuit voltage is higher than expected. Possible short to battery, failed coil/igniter, wiring fault, or ECM driver issue. Inspection of coil B, wiring, connector, and comparing to known-good channels recommended.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-3 hours

Repair manuals