What it means
Ignition H control signal stuck high — short to B+. 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 that triggers its assigned coil or coil group. This code sets when the H signal remains above its expected level, often because the signal wire is shorted to battery voltage.
Common causes
Most likely first.
- Short to B+
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
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 determine when the ignition H high-signal fault appears.
- Inspect the H circuit harness and connectors for pinched wiring, corrosion, loose terminals, or contact with a powered wire.
- Identify the H circuit and its assigned coil or coil group using the manufacturer's wiring information.
- With the circuit isolated as specified, test the H signal wire for an unwanted connection to battery voltage and check continuity.
- If the wiring checks out, test the assigned coil and the module's H output using the manufacturer's procedure.
Common fixes
- Reconnect loose ignition H terminals and clean corrosion.
- Repair wiring shorted to battery voltage or pinched against a powered 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?
A faulty H signal can cause misfires, hard starting, or power loss; avoid demanding driving and stop if the engine runs severely unevenly. If the check-engine light flashes, stop as soon as it is safe because misfires can damage the catalytic converter.
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.