P0118 on Mazda vehicles
Coolant Temp Sensor High Input — what it means on a Mazda, whether it's safe to drive, and the fixes by model and year.
P0118 on a Mazda means coolant temp sensor high input. Most vehicles stay drivable short-term, but diagnose it promptly. The most common cause is disconnected or unlatched ect sensor connector (typically $0–$50). Pick your Mazda model below for its known failure patterns, recalls, and TSBs.
What does P0118 mean on a Mazda?
P0118 is set when the engine control module reads the engine coolant temperature sensor signal voltage above the calibrated maximum — typically a reading that would represent an unrealistically cold coolant temperature (often −40 °F / −40 °C). This is the open-circuit fingerprint for the ECT sensor: a disconnected sensor, a broken signal wire, or a sensor failed open internally.
P0118 is a standardized OBD-II code, so its definition is the same on every Mazda. What differs by model and engine is which cause is most likely — pick your Mazda model below for a diagnosis tuned to its known failure patterns, recalls, and TSBs.
Is it safe to drive a Mazda with P0118?
In most cases a Mazda stays drivable for short trips with P0118 active, but diagnose and repair it promptly. This is a moderate-severity code — ignoring it can lead to further damage or a failed emissions test. Exact tolerance depends on the model and engine.
What causes P0118 on a Mazda?
| Cause | Likelihood | Estimated repair (USD) |
|---|---|---|
| Disconnected or unlatched ECT sensor connector | Most common | $0–$50 |
| Broken or chafed ECT signal wire (open circuit) | Common | $80–$350 |
| Internally failed ECT sensor (element opened) | Common | $30–$200 |
| Corroded sensor connector pins | Common | $30–$200 |
| Damaged sensor body from coolant leak or freeze | Occasional | $50–$250 |
| Failed PCM signal input (rare) | Rare | $400–$1,500 |
Repair costs are typical US ranges and vary by Mazda model, model year, and labor rate. A diagnostic trouble code is a symptom, not a guaranteed failed part — confirm the root cause before replacing anything.
P0118 by Mazda model
Select your Mazda model and year for a P0118 diagnosis tuned to that vehicle's failure patterns, recalls, and TSBs.
Mazda CX-5
205 NHTSA owner complaints · 1 recalls on record across the years covered below.
Complaint and recall counts are NHTSA totals for the model years covered on this site, not counts specific to P0118.
P0118 on other makes
Other codes on Mazda vehicles
P0118 on a Mazda: frequently asked questions
What does diagnostic trouble code P0118 mean on a Mazda?
P0118 is set when the engine control module reads the engine coolant temperature sensor signal voltage above the calibrated maximum — typically a reading that would represent an unrealistically cold coolant temperature (often −40 °F / −40 °C). This is the open-circuit fingerprint for the ECT sensor: a disconnected sensor, a broken signal wire, or a sensor failed open internally. P0118 is a standardized OBD-II code, so the definition is the same on every Mazda — which cause is most likely varies by model and engine.
What are the symptoms of P0118 on a Mazda?
Check Engine Light is illuminated. Temperature gauge reads zero or stays cold. Difficult cold start with rich-running symptoms. Cooling fans may run constantly (ECM thinks coolant is dangerously cold). Slightly reduced fuel economy. Cold-running engine doesn't warm up properly per the gauge. Possible hard start when the engine is hot (ECM commands cold-start enrichment)
What causes P0118 on a Mazda?
Disconnected or unlatched ECT sensor connector (most-common). Broken or chafed ECT signal wire (open circuit) (common). Internally failed ECT sensor (element opened) (common). Corroded sensor connector pins (common). Damaged sensor body from coolant leak or freeze (occasional). Failed PCM signal input (rare) (rare)
Is it safe to drive a Mazda with P0118?
In most cases a Mazda stays drivable for short trips with P0118 active, but it should be diagnosed and repaired promptly — this is a moderate-severity code. Ignoring it can lead to further damage or a failed emissions test. Exact tolerance depends on the model and engine.