P031D: Ignition D Control Signal Circuit/Open

What it means

The ignition D control signal circuit is open — typically the PCM drive line for the first ignition coil group has lost continuity.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The PCM uses the Ignition D control circuit to command an ignition channel and monitors whether the circuit has electrical continuity. This code sets when the Ignition D path is open, so the commanded signal may not reach the associated ignition hardware.

Common causes

Most likely first.

1. Open wire between PCM and coil
2. Pin pushed back out of connector body
3. Cracked solder joint inside the module or sensor

Symptoms

• Rough running or misfire
• Hard starting or no start
• Reduced engine power

How to diagnose it

1. Capture freeze-frame data and check live misfire or ignition data to determine whether the open circuit is causing a current running or starting problem.
2. Inspect the Ignition D wiring route and connectors for a broken wire, loose plug, corrosion, or a terminal pushed back in its housing.
3. Use the vehicle wiring information to check continuity through the Ignition D control path and locate any interruption.
4. Check connector terminal fit and inspect the wiring where it bends, rubs, or enters the connector.
5. If continuity is intact to the module, test the ignition hardware and control-module output according to the manufacturer's procedure.

Common fixes

• Repair or replace a broken Ignition D control wire.
• Reseat a pushed-back terminal and repair a damaged connector housing.
• Clean or replace corroded terminals and restore a secure connection.
• Replace a confirmed faulty ignition component or module.

Can I keep driving?

If the engine is misfiring or running roughly, limit driving and avoid heavy loads; an open Ignition D circuit can leave an ignition channel inoperative and increase emissions. Do not drive if it stalls or cannot be started reliably.