P1116
GMThe Powertrain Control Module (PCM) has detected that the input from the Engine Coolant Temperature (ECT) sensor is outside of its expected operating range or self-test limits.
Medium SeverityThis code indicates that the Engine Coolant Temperature (ECT) sensor is sending an implausible signal to the PCM, suggesting it's either faulty or the engine's coolant temperature is genuinely out of expected parameters. This can lead to incorrect fuel mixture adjustments, affecting fuel economy and engine performance, and potentially causing issues with the cooling fan operation.
⚠️ Before You Begin (Safety First)
Always allow the engine to cool completely before working on any part of the cooling system to prevent severe burns. When disconnecting electrical components, it is advisable to disconnect the negative battery terminal to prevent electrical shorts or damage to the vehicle's computer system.
Common Symptoms
- Check Engine Light illumination
- Poor fuel economy
- Engine running rich or lean
- Hard starting, especially when cold
- Engine overheating (if sensor reads too low)
- Engine cooling fan running constantly or not at all
- Black smoke from the exhaust
- Idling issues
Common Causes
- Faulty Engine Coolant Temperature (ECT) sensor
- Low engine coolant level
- Wiring harness issues (chafed, corroded, open, or shorted wires)
- Poor electrical connection at the ECT sensor
- Faulty thermostat (less common, but can cause out-of-range temperatures)
- Powertrain Control Module (PCM) failure (very rare)
Frequently reported on: Chevrolet Silverado (2000-2013), GMC Sierra (2000-2013), Chevrolet Tahoe (2000-2014), Pontiac Grand Prix (1997-2008), Buick LeSabre (2000-2005)
Diagnostic Steps
- Use an OBD-II scanner to confirm P1116 is the only code present and check for any related cooling system codes.
- Visually inspect the Engine Coolant Temperature (ECT) sensor and its electrical connector for any signs of damage, corrosion, or loose connections.
- Check the engine coolant level in both the radiator and the reservoir; top off if necessary.
- Test the resistance of the ECT sensor using a multimeter and compare it to manufacturer specifications at various temperatures.
- If the sensor tests faulty or shows signs of damage, replace the ECT sensor.
- After replacement, clear the diagnostic trouble code using an OBD-II scanner.
👨🔧 When to Call a Professional
If the Engine Coolant Temperature (ECT) sensor has been replaced and the P1116 code persists, or if you suspect wiring damage or a fault within the Powertrain Control Module (PCM), it is time to consult a professional mechanic for advanced diagnostics.
Commonly Asked Questions
Can I drive with a P1116 code?
It is generally not recommended to drive for extended periods with a P1116 code, as it can lead to poor fuel economy, emissions issues, and potentially engine overheating or poor performance.
Is P1116 an expensive repair?
Typically, replacing a faulty Engine Coolant Temperature (ECT) sensor is a relatively inexpensive repair, often costing under $50 for the part itself, plus minimal labor if done professionally.
How does the ECT sensor work?
The Engine Coolant Temperature (ECT) sensor measures the temperature of the engine's coolant and sends this data to the Powertrain Control Module (PCM), which uses it to adjust fuel delivery, ignition timing, and cooling fan operation.
Can low coolant cause a P1116 code?
Yes, extremely low engine coolant can cause the ECT sensor to read an out-of-range temperature, as it might not be fully submerged in coolant, or the engine could genuinely be overheating due to lack of coolant.
What if replacing the ECT sensor doesn't fix P1116?
If replacing the sensor doesn't resolve the code, the issue likely lies with the wiring harness to the sensor, the electrical connector, or, in rare cases, the Powertrain Control Module (PCM) itself. Further electrical diagnosis would be required.