P0118 Code: Meaning, Symptoms, Causes & Fix

Overview

Code P0118 indicates a fault in Engine Coolant Temperature Circuit High Input, typically within powertrain controls.

Symptoms

check engine light
rough operation in certain conditions
reduced performance

Common causes

Open circuit in wiring affecting engine coolant temperature circuit high input
Broken terminal inside harness
Connector pin damage/corrosion or harness stress near related components

How to diagnose P0118

Confirm P0118 and capture freeze-frame data with a professional scan tool.
Inspect wiring, connectors, and grounds related to engine coolant temperature circuit high input for obvious defects.
Use a continuity test from module pin to component to identify opens/high resistance.
Check for related DTCs to identify the root-cause chain before replacing parts.
After repair, clear codes and confirm readiness monitors complete without recurrence.

Severity of code P0118

Moderate: This code is moderate severity: the vehicle may still operate, but fault progression can increase repair cost over time.

Can you drive with P0118?

Most vehicles can be driven short-term with P0118, but postpone heavy load/highway driving until repaired.

If the warning lamp is flashing or drivability/safety is affected, avoid driving and diagnose immediately.

How to fix it (step-by-step)

Repair obvious wiring/connector faults first to prevent repeat parts replacement.
Address the root fault mode (open) in the engine coolant temperature circuit high input circuit/system.
Apply the required relearn/adaptation procedure if specified by service information.
Road-test and verify P0118 remains cleared under the conditions that originally set the code.

Fix options

Restore continuity and verify pin tension.
Repair open circuit and secure connector lock.
Clear DTCs and verify with live data and completed drive cycle.

Typical repair cost

$200-$900

Common mistakes when diagnosing P0118

Replacing parts without verifying voltage, ground, and signal integrity first.
Ignoring related stored/pending codes that indicate upstream faults.
Skipping post-repair verification drive cycle and readiness checks.

P0118 in common vehicles

P0118 appears across makes such as BMW, Mercedes-Benz, Audi, Volvo. Failure patterns differ by platform: wiring routes, software calibration, and component supplier revisions can change root cause.

Frequently asked questions

What causes P0118?

P0118 is commonly set by open faults affecting engine coolant temperature circuit high input.

How much does it cost to fix P0118?

For P0118, repair costs are typically $200-$900 depending on exact root cause, labor rates, and part quality.

Can I clear P0118 without repair?

You can clear P0118 temporarily, but the code usually returns until the underlying fault is corrected.