C1112 — ABS Power Relay Coil Short Circuit To Ground

What are the symptoms of C1112?

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

What is the most common cause of C1112?

The most common causes are: faulty ignition control circuit in the ECM, moisture or oil in the spark plug wells, failed ignition coil or coil pack.

How do I diagnose C1112 myself?

Start with a scan: confirm C1112, 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.

How much does it cost to fix C1112?

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

Is it safe to drive with C1112?

Drive with caution and avoid load. Ignition faults cause misfires that quickly overheat and destroy the catalytic converter; if the Check Engine Light flashes, stop and fix it first.

When the check engine light comes on and a scan tool reveals code C1112, your vehicle is alerting you to a specific electrical fault: the control module has detected a short circuit to ground in the ABS power relay coil circuit. This falls within the chassis electronics category of OBD2 diagnostics, affecting the anti-lock braking system's power distribution rather than the engine itself. The ABS module continuously monitors the relay circuit while you drive, checking for proper voltage and ground conditions. When these readings fall outside acceptable parameters for the required number of drive cycles, the module stores C1112 and activates the warning light.

The ABS power relay acts as an electrically controlled switch that routes electrical current to the anti-lock pump motor and related components. When the relay coil develops a short to ground, the module cannot reliably energize or de-energize the relay, potentially leaving the ABS system without proper power or causing unexpected activation. Freeze frame data stored alongside C1112 captures the exact vehicle conditions—speed, brake input, voltage levels—at the moment the fault occurred, giving you a starting point for diagnosis.

Ignition system symptoms often accompany C1112 because the ABS relay circuit shares power sources with other vehicle systems. When electrical distribution is disrupted, related components can exhibit erratic behavior.

Symptoms of C1112

• Check Engine Light or ABS warning light illuminated
• Hard starting, particularly in damp or wet conditions
• Engine misfires during acceleration or at idle
• Noticeable loss of engine power with jerking or stuttering
• Increased fuel consumption compared to normal driving patterns
• Rough idle or intermittent stalling at low speeds

Common Causes of C1112

Damaged wiring or corroded connectors in the ABS relay circuit represent the most frequent trigger for C1112. Wire chafing from vibration, moisture intrusion into connectors, and thermal cycling damage all create paths to ground that the module interprets as a fault.

Worn or improperly gapped spark plugs also commonly produce the misfire symptoms associated with this code. Plugs that have exceeded their service interval develop gaps that force the ignition system to work harder, creating electrical stresses throughout the power distribution network.

Failed ignition coils or coil packs can generate voltage spikes that propagate through shared electrical pathways, potentially triggering ABS circuit faults even though the coil itself may not be directly connected to the relay.

Moisture or oil contamination in spark plug wells creates conductive paths that produce symptoms mimicking electrical shorts, confusing module logic and triggering C1112.

Excessive resistance in ground connections throughout the chassis can cause voltage feedback that the module interprets as a short circuit condition in the relay coil circuit.

How to Diagnose C1112

Begin by connecting an OBD2 scanner to confirm C1112 is stored and record the freeze frame data. This snapshot shows engine speed, load, temperature, and vehicle speed when the fault was detected, helping you replicate those exact conditions during testing.

Check for any additional stored codes that often point to the root cause. Look up manufacturer technical service bulletins for your specific make, model, and year—many C1112-related issues have documented factory fixes or software updates available through the manufacturer website or NHTSA database.

Perform a thorough visual inspection of the wiring harness and connectors in the ABS circuit. Look for damaged insulation, broken wires, corrosion buildup, and loose or pushed-out terminals that could create unintended ground paths.

Test the relay coil resistance with a multimeter according to manufacturer specifications. Compare readings against known-good values and check for continuity to ground that should not exist.

Swap suspected ignition coils between cylinders and monitor whether the fault code migrates with the component, indicating a failing coil rather than a circuit issue.

Clear the code, complete a full drive cycle including conditions matching the freeze frame data, then rescan to verify whether C1112 returns.

Repair Options and Costs

Spark plug replacement addresses worn electrodes and incorrect gaps that force the ignition system to draw excessive current. Most vehicles require four to eight plugs depending on cylinder count, with parts typically running $40 to $150 and labor adding another $50 to $100 at independent shop rates. Total cost: $90 to $250.

Ignition coil replacement fixes voltage delivery failures that stress the entire electrical system. Individual coils cost $50 to $150 each, with four to eight units