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How to Reset Temperature Gauge and Fix P0118 in 2005 Chevrolet Silverado 1500 5.3L

Model: 2005 Chevrolet Silverado Fault Code: P0118 Posted: 2014-04-08 13:48

My 2005 Chevrolet Silverado 1500 5.3L is showing an abnormal temperature gauge reading, consistently pegging above 260°F and now displaying the 'hot' warning sign. I've already replaced both the thermostat and the engine block temperature sensor (ECT), but the issue persists. The gauge does not return to normal readings (like 160°F) during warm-up; instead, it stays elevated even after the engine has warmed up. The vehicle is stock with no aftermarket modifications. I've been advised that a diagnostic scan may reveal fault codes—specifically P0118—which indicates an abnormal signal from the engine coolant temperature (ECT) sensor. I'm seeking help to understand what else might be causing this behavior and how to properly diagnose or reset the gauge reading.

Related fault codes
P0118
Comments (7)
Anonymous 2014-04-08 14:01

Perform a diagnostic scan to check for error codes—especially if the Check Engine Light is on. Verify whether the engine is actually overheating by checking coolant temperature, overflow tank levels, and radiator pressure. At startup, does the gauge immediately read 260°F or does it rise gradually? This information can help determine if the issue lies in sensor readings or system function. I suspect the DTCs (like P0118) will provide critical clues about what's wrong.

Anonymous 2014-04-08 14:04

The gauge does not return to normal after warming up. It stays elevated, and while it warms gradually from its current level, it never drops back to the standard 160°F range during operation.

Anonymous 2014-04-08 14:05

I'm unsure what tests to perform on the 5-amp ECT sensor wiring—any guidance on how to verify proper function?

Anonymous 2014-04-08 14:17

Is the vehicle using a 195°F thermostat? Yes, I've confirmed that. What does '5 amps' refer to? It may be a typo or misunderstanding—likely referring to the sensor's power supply or wiring current. I believe scanning for codes will reveal more accurate diagnostics. PS: This is a stock vehicle with no aftermarket parts installed.

Anonymous 2014-04-08 14:22

Yes, I replaced the thermostat with a 195°F unit. The P0118 code remains present even after replacement. No modifications have been made to the vehicle.

Anonymous 2014-04-08 15:13

The Powertrain Control Module (PCM) is detecting an abnormally high return voltage from the ECT sensor. Ensure that the ECT harness is properly routed and not near high-voltage wires. There are typically two wires at the ECT: yellow and black or brown. Using a digital multimeter (DVOM): - Perform a KOEO test (engine off, key on). - Unplug the sensor probe and measure the yellow wire—should read approximately 4.9 volts. - Measure the ground wire—should show no voltage. - Reconnect the sensor and measure the ground wire again—what is the reading? If there are three wires on this sensor, please clarify so further testing can be directed.

Anonymous 2014-04-08 17:10

I'll follow up on this tomorrow with more detailed test results and observations.