Engine Coolant Temperature Sensor 1
The ECM has detected a fault with the Engine Coolant Temperature (ECT) sensor 1.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The Engine Control Module (ECM) checks the coolant temperature using a sensor that should read around 195-220°F under normal operating conditions. If this sensor fails or if the connection is compromised, the ECM doesn't get the right temperature readings, affecting engine performance.
What the computer is actually seeing
The ECM monitors the temperature signal from ECT sensor 1, which should fluctuate based on coolant temperature. An abnormal voltage (typically 0.5V-4.5V) is detected indicating a failure in range or response time.
What a healthy reading looks like
ECT sensor should read between 195°F and 220°F during standard operating temperature. Resistance when cold should be approximately 5,000-10,000 ohms and decreases with heat.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Inspect the ECT sensor wiring for any visible damage or corrosion. Check for good connections at the ECM and sensor. If damaged, repair or replace as necessary. DECISION: If wiring is good, proceed to next step; if damaged, fix and retest.
Common causes
- Faulty ECM
- Open circuit in ECT sensor wiring
- Short to ground or power in the ECT sensor circuit
- Defective Engine Coolant Temperature sensor
- Corroded or loose connector at the ECT sensor
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Yes, but it's recommended to fix it soon as it can cause overheating or emissions issues.
Will the problem come back after fixing?
If the wiring and connectors are in good shape and the sensor is replaced, it shouldn't return.
Why does this code appear with SPN 2191?
SPN 2191 is often related to a different ECT sensor or the same circuit and can indicate related issues.
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