What it means
The ignition H 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
Ignition control signal H is an engine control module drive circuit used to trigger its assigned coil or coil group. This code sets when the module detects an open circuit in the H control path, so the ignition drive signal cannot complete its intended route.
Common causes
Most likely first.
- Open wire between PCM and coil
- Pin pushed back out of connector body
- Cracked solder joint inside the module or sensor
Symptoms
- Check engine light on or flashing
- Engine misfire or rough running
- Power loss or hesitation
- Hard starting
How to diagnose it
- Record freeze-frame data and check misfire information to identify when the ignition H fault occurs and how the engine responds.
- Inspect the ignition H wiring path and connectors for loose plugs, damaged insulation, or a terminal pushed back in its connector.
- Use the manufacturer's wiring information to locate the H circuit connections, then check continuity with the system safely powered down as specified.
- Inspect the coil or coil group assigned to ignition H and its connector for damage or a poor connection.
- If the wiring and coil connections pass, follow the manufacturer's procedure to test the module's H output and related components.
Common fixes
- Reconnect a loose ignition H connector or restore a pushed-back terminal.
- Repair an open wire in the ignition H control circuit.
- Replace a damaged connector or terminal.
- Replace a failed coil or coil group assigned to H if testing confirms it.
- Repair or replace a module only if its H output is confirmed faulty.
Can I keep driving?
If the check-engine light is flashing or the engine is misfiring, stop driving as soon as it is safe because unburned fuel can overheat and damage the catalytic converter. If the light is steady and the engine runs smoothly, keep any trip short and avoid heavy acceleration.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.