C1242 — ABS Outlet Valve Coil LR Circuit Failure

chassis (brakes/steering/suspension)

Is it safe to drive?

Drive with caution 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.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm C1242 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many C0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the ignition system for damage, corrosion, chafing or poor contact.
Subsystem check Swap the coil to another cylinder and see if the fault code follows it.
Subsystem check Inspect spark plugs for wear, oil or carbon tracks and check plug gaps.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm C1242 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for C1242 (parts and labor, USD, independent shop rates): Replace spark plugs: $90–$250; Replace an ignition coil: $150–$380; Repair coil wiring or connector: $80–$250. Overall, fixing C1242 usually costs between $80 and $380. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

What does OBD2 code C1242 mean?

ABS Outlet Valve Coil LR Circuit Failure (C1242): a chassis (brakes/steering/suspension) fault affecting the ignition system. Short, gentle driving to a shop is usually possible. Most often caused by failed ignition coil or coil pack, moisture or oil in the spark plug wells, faulty ignition control circuit in the ECM.

How much does it cost to fix C1242?

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 C1242?

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.

How do I diagnose C1242 myself?

Start with a scan: confirm C1242, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the ABS outlet valve coil LR circuit, and verify the suspect component against live data before buying parts.

What is the most common cause of C1242?

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

Code C1242 refers to an electrical fault within your vehicle's anti-lock braking system, specifically involving the left-rear outlet valve coil circuit. In plain terms, the ABS module has detected that the solenoid valve responsible for releasing brake pressure at the rear-left wheel is not operating within its designed electrical parameters. When the module performs its routine self-check and finds the coil's resistance or signal outside acceptable limits, it stores C1242 and illuminates the ABS warning light on your dashboard.

Modern ABS units use electromagnetic solenoid valves to modulate brake pressure at each wheel independently. The outlet valve — sometimes called the "dump valve" — opens to release pressure when the system needs to prevent a wheel from locking during an emergency stop. Each valve relies on a coil that receives an electrical signal from the ABS controller. If that coil fails electrically — whether through an open circuit, a short, or excessive resistance — the module logs C1242. The stored freeze frame data captures the exact vehicle speed, brake pedal position, and system voltage at the moment the fault was confirmed, giving you a reliable starting point for diagnosis.

Symptoms of C1242

The way C1242 affects your vehicle depends on how severely the left-rear outlet valve has failed:

ABS warning light stays on — this is the most immediate and obvious indicator that the module has detected the fault
Standard brake warning light may also activate if the module registers a broader system concern alongside C1242
Reduced braking effectiveness during panic stops — the affected wheel may lock because the outlet valve cannot release pressure on command
Unusual brake pedal feel — the pedal may feel harder or softer than normal depending on how the fault affects valve operation
Traction control or stability control warning lights may accompany C1242 on vehicles where these systems share the ABS module
A slight pull to one side under heavy braking if the left-rear wheel does not release properly
No noticeable symptoms during normal, gentle driving — many drivers only discover the fault during routine braking or a dashboard inspection

Common causes of C1242

The root cause of C1242 typically falls into one of three categories — electrical, hydraulic, or electronic. Based on real-world repair records, the most likely culprits are:

Failed ABS outlet valve coil — the solenoid coil inside the hydraulic unit itself burns out or develops an open circuit, which is the single most common reason for this code
Damaged wiring or poor connector contact between the ABS module and the left-rear valve coil, including chafed insulation or corroded terminals
A faulty ABS module that cannot properly drive the valve circuit, though this is less frequent than a localized coil or wiring failure
Hydraulic pump motor issues that create voltage irregularities the module misinterprets as a valve circuit failure
Water intrusion into the ABS harness connectors, especially on vehicles exposed to road salt or frequent wet conditions
Low system voltage from a weak battery or failing alternator causing the module to misread sensor values
Software calibration issues on certain makes and models where the module's programming does not match the installed hardware

How to diagnose C1242

Working through C1242 methodically keeps you from replacing parts unnecessarily. Follow these steps in order:

Connect an OBD2 scanner and confirm that C1242 is present. Record the freeze frame data — this shows the vehicle's speed, brake status, and system voltage when the module logged the fault. Clear the code and road-test the vehicle to see if it returns.
Inspect the wiring harness going to the ABS module and the connector at the hydraulic unit. Look for frayed wires, broken insulation, loose pins, or corrosion. A poor connection is one of the easiest and most frequent fixes for this code.
Check system voltage with a multimeter. A weak battery or unstable alternator output can cause the ABS module to set false valve circuit codes. Verify that the module is receiving clean, consistent power and proper ground.
Measure the resistance of the suspect valve coil if you have access to the module's wiring diagram and can probe the relevant terminals. Most valve coils fall within a specific resistance range — consult your vehicle's service manual for the exact specification.
Research TSBs for your specific make and model using the manufacturer website or NHTSA's database. Some vehicles have known software updates or hardware revisions that resolve C1242 without any physical part replacement.
If the valve coil itself is confirmed failed, the hydraulic unit may need replacement. On some vehicles the valve assembly is integral to the ABS pump and cannot be serviced separately.

Repair options and costs

Addressing C1242 almost always requires working on the ABS hydraulic assembly or its electrical connections. Here are the typical repair scenarios and what they cost at an independent shop in USD:

Wiring or connector repair — cleaning corroded terminals, soldering broken wires, or replacing a damaged harness segment typically runs $80–$250 depending on accessibility and labor time
ABS valve coil or solenoid replacement — if your vehicle's hydraulic unit allows individual valve replacement, the part and labor generally total $200–$500, though this varies widely by chassis design
Full ABS hydraulic unit replacement — the most expensive scenario, where the entire pump and valve assembly is swapped as a single component, usually costs $600–$1,200 for parts and labor

Parts costs alone for a replacement hydraulic unit range from roughly $350 to $800 depending on whether you use new, remanufactured, or used components.

How much does it really cost to fix C1242?

The total bill hinges entirely on what is actually faulty. In most straightforward cases involving nothing more than a broken wire or corroded connector, expect to pay between $80 and $250 for a clean electrical repair. If the valve coil inside the hydraulic unit has failed, you are looking at $200–$500 depending on whether the shop can replace just the solenoid or must install a complete assembly. The worst-case scenario — a failed ABS pump module — pushes costs toward $600–$1,200. One practical tip: an accurate electrical diagnosis before ordering any major components almost always saves you money, because the valve coil failure is far less common than a wiring issue.

Can you drive with C1242?

Use caution. C1242 carries a caution-level severity — your conventional brakes remain functional, but anti-lock and traction control features are compromised. During normal, moderate braking you may notice no difference at all. However, in an emergency stop or on a slippery surface, the left-rear wheel may lock without the ABS system to prevent it, extending your stopping distance and reducing your ability to steer around an obstacle. Drive conservatively, avoid hard braking, and have the fault diagnosed and repaired before any situation that demands maximum stopping performance. Do not ignore the warning light indefinitely.