B1558 — Ignition Run/Start Circuit Short To Ground

Will B1558 clear itself?

Sometimes B1558 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

What are the symptoms of B1558?

Drivers most often notice: Check Engine Light on, increased fuel consumption, misfires under load or at idle, hard starting, especially in damp weather.

How do I diagnose B1558 myself?

Start with a scan: confirm B1558, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the ignition system, and verify the suspect component against live data before buying parts.

What is the most common cause of B1558?

The most common causes are: worn spark plugs or wrong plug gap, failed ignition coil or coil pack, faulty ignition control circuit in the ECM.

How much does it cost to fix B1558?

Replace spark plugs — $90–$250; Repair coil wiring or connector — $80–$250; Replace an ignition coil — $150–$380. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

When your engine control module detects that the ignition run circuit has collapsed to ground instead of holding proper battery voltage, it logs trouble code B1558. This specific fault targets the pathway that powers your ignition coils during engine cranking and run mode. The module constantly watches this circuit because it needs reliable voltage to fire the spark plugs in the correct sequence. A short to ground means electricity never reaches the coil, or worse, the circuit bleeds power to the chassis instead of through the intended path. B1558 belongs to the body network category on most vehicles, which means the fault may route through the body control module even though the actual problem lives in the engine compartment wiring.

The PCM does not trigger B1558 from a single bad reading. Internal logic requires the fault condition to repeat or persist under specific operating conditions before the module lights the check engine lamp. When it does store the code, it also captures freeze frame data showing engine load, RPM, coolant temperature, and vehicle speed at the moment of failure. Those readings tell you exactly what the engine was doing when things went wrong, which is invaluable when you need to reproduce the failure during testing.

Common Symptoms of B1558

• Check Engine Light illuminated
• Rough idle or noticeable misfires under load
• Decreased fuel economy
• Hard starting, especially in damp or wet weather
• Reduced engine power and hesitation during acceleration
• In severe cases, engine enters limp-home mode with limited RPM

What Causes B1558?

• Damaged or corroded ignition coil wiring and connectors
• Failed ignition coil or coil pack
• Worn, contaminated, or incorrectly gapped spark plugs
• Short circuit in the ignition control wire between the PCM and coil
• Faulty ignition driver circuit inside the engine computer (less common)
• Aftermarket alarm or remote start installation that interferes with the ignition circuit

How to Diagnose B1558

1. Connect an OBD2 scanner and verify B1558 is stored. Save the freeze frame data — note the engine load, RPM, temperature, and speed values recorded when the fault occurred.
2. Review any additional stored codes. Related trouble codes often point to the root cause, such as a failing sensor that shares the same circuit or power source.
3. Check manufacturer technical service bulletins for your specific make and model. Many body-network and ignition issues have documented factory fixes, software updates, or known failures.
4. Perform a visual inspection of all ignition circuit wiring and connectors. Look for chafed insulation, broken wires, corrosion at the connector pins, or evidence of heat damage near the coils.
5. Test the suspected coil by swapping it with a known-good unit from another cylinder. If the fault code moves to the new cylinder, the coil is faulty.
6. Remove and inspect the spark plugs. Check for worn electrodes, oil fouling, carbon tracking on the ceramic, and verify the gap matches factory specifications.
7. Clear the code, start the engine, and complete a drive cycle that replicates the freeze frame conditions. The code should stay cleared if the repair was successful.

How to Fix B1558

Address the cheapest and most likely causes before spending money on major components. Repair options for B1558 include the following:

• Replace spark plugs: $90–$250
• Repair damaged coil wiring or connector: $80–$250
• Replace an ignition coil or coil pack: $150–$380

How Much Does It Cost to Fix B1558?

The total repair bill depends entirely on which part is actually faulty. At independent shop rates in the United States, parts and labor break down as follows. Spark plug replacement typically runs $90 to $250 depending on engine design and labor time. Wiring harness or connector repair for the ignition circuit generally costs $80 to $250, with most of that being labor if the damage is in a hard-to-reach location. A complete ignition coil replacement usually lands between $150 and $380. Most B1558 repairs end up in the $80 to $380 range. Spending time on accurate diagnosis before buying parts almost always saves money, because the most expensive scenario is rarely where you want to start.

Can You Drive with B1558?

Use caution if the check engine light is steady and the engine runs reasonably well. Avoid hard acceleration and heavy loads. The underlying ignition failure causes misfires that dump unburned fuel into the exhaust, and that fuel load overheats the catalytic converter quickly. If the check engine light begins flashing, stop driving immediately — flashing indicates an active misfire that is actively destroying your catalytic converter.

Related OBD2 Codes

• B1500: Lamp Turn Signal Left Circuit Open
• B1501: Lamp Turn Signal Left Circuit Short To Battery
• B1502: Lamp Turn Signal Left Circuit Short To Ground
• B1503: Lamp Turn Signal Right Circuit Failure
• B1504: Lamp Turn Signal Right Circuit Open
• B1505: Lamp Turn Signal Right Circuit Short To Battery