P031C

Code

Generic P — Powertrain

Ignition C Control Signal Circuit High

Brand: Generic

Type: P — Powertrain

Views: UK: 20 EN: 32 RU: 32

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Short to battery/ignition voltage on Ignition C driver circuit
Open or damaged wiring harness or chafed insulation causing intermittent/incorrect voltage
Corroded or loose connector at the coil or ignition module
Faulty ignition coil, coil-on-plug (COP) module or ignition module
Faulty PCM/ECM ignition driver or internal PCM fault
Poor or missing ground on ignition coil/ignition module

Read and record freeze frame data and related codes (misfire and coil codes)
Inspect wiring harness and connectors for the Ignition C coil/ignition module for damage, corrosion, loose pins or water ingress
Backprobe the coil control pin with key ON and engine cranking/started to observe voltage behaviour
Check for continuity to PCM and shorts to battery (B+) and ground using a multimeter
Measure coil primary resistance and compare to OEM spec (replace if out of spec)
Swap Ignition C coil with another cylinder’s coil (if same type) to see if the code follows the coil

Typical behavior (generic): control circuit switches between near 0 V (driver ON to ground) and battery voltage (~12 V) when OFF. A ‘high’ fault means the circuit stays near battery voltage when it should be switching low.
High condition threshold (generic): persistent voltage above ~9–11 V where the controller expects switching to ground. Check OEM spec for exact thresholds.
Coil primary resistance (typical ranges vary by design): low-ohm coils commonly ~0.3–3 Ω; high-voltage secondary thousands of ohms — consult OEM specs before replacement.

Retrieve full DTC list and freeze frame; note engine conditions when code set (temp, rpm, load).
Visually inspect Ignition C coil/module, connector and wiring for damage, melting, corrosion or pin push-out. Repair any visible faults.
With ignition OFF, disconnect the Ignition C coil/module connector. Check for unintended continuity between the control wire and battery (+) and between control wire and ground. Repair shorts/open circuits as found.
Reconnect and backprobe the control circuit at the coil with a multimeter or scope. With key ON and engine cranking/started, verify the driver switches to ground (pulses near 0 V). If circuit remains high (≈ battery voltage) when it should switch low, suspect short to B+ or bad driver/coiI.
Swap the Ignition C coil with another known-good coil (if same type) and clear codes. If code moves to the other cylinder, the coil is likely bad. If code remains on C, suspect wiring or PCM driver.
If bench checks point to wiring/connector repair those issues (repair, replace harness, clean connectors). After repairs clear codes and retest.
If wiring and coil test good but circuit still incorrect at PCM, test PCM driver output per service manual or consult manufacturer procedures; replace PCM only after confirming external circuit is good.
After repair, clear codes and perform a road/test cycle to confirm the fault does not return.