What it means
Ignition H control signal stuck low — short to ground. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
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 for its assigned ignition coil or coil group. This code sets when the circuit is held below its expected signal level, commonly because the H signal wire is shorted to ground.
Common causes
Most likely first.
- Short to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check engine light on or flashing
- Engine misfire or rough running
- Power loss or hesitation
- Hard starting
How to diagnose it
- Save freeze-frame data and check misfire information to see when the ignition H low-signal fault and rough running occur.
- Inspect ignition H connectors and the harness for chafing, moisture, corrosion, or a terminal contacting ground.
- Use the manufacturer's wiring information to verify the H circuit connections and identify its assigned coil or coil group.
- With the circuit isolated as specified by the manufacturer, test the H signal wire for a short to ground and check continuity.
- If the wiring passes, test the assigned coil and the module's H output using the manufacturer's procedure.
Common fixes
- Clean and secure corroded or loose ignition H connector terminals.
- Repair chafed wiring or a confirmed short to ground in the H circuit.
- Replace a damaged connector or terminal.
- Replace a failed coil 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 flashes or the engine misfires, stop driving as soon as it is safe because continued misfiring can damage the catalytic converter. With a steady light and smooth running, drive only a short distance and avoid heavy loads.
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.