Owner's Problem Description
The owner of a 2017-2020 GMC Acadia V6 is experiencing issues where the temperature gauge drops to zero while driving, accompanied by power steering warnings and ineffective A/C. They suspect a faulty coolant temperature sensor and have purchased a replacement but are unable to locate the sensor for installation. They are seeking a diagram or detailed instructions to help identify its position.
Professional Technical Analysis
The 2017-2020 GMC Acadia V6 is equipped with a coolant temperature sensor that plays a critical role in the engine management system. This sensor is typically located under the intake manifold, necessitating the removal of the coolant thermostat housing for access. When the temperature gauge drops to zero, it can indicate a faulty sensor, which may lead to incorrect readings that affect the power steering and A/C performance. The vehicle’s symptoms suggest that the PCM (Powertrain Control Module) is not receiving accurate temperature data, which can lead to reduced engine performance and improper operation of various systems. It is essential to confirm the sensor's functionality and wiring integrity before replacement. Given the age and mileage of the vehicle, it is also prudent to inspect related components for wear or damage that may contribute to the symptoms.
Possible Causes
Most common causes (ordered by frequency):
- Coolant Temperature Sensor Failure: The coolant temperature sensor may have failed, resulting in the PCM receiving incorrect temperature readings. This can cause the gauge to drop to zero and affect various engine functions. The sensor's resistance should be tested at different temperatures; at 20°C, it should be around 2,500-3,000 ohms, decreasing as temperature increases. A defective sensor may show erratic resistance values. - Zero reading on temperature gauge, error codes related to temperature sensor (P0117, P0118), inconsistent A/C performance.
- Wiring Issues: Damaged or corroded wiring harness connected to the coolant temperature sensor can lead to poor connectivity, causing the PCM to misinterpret the data. A visual inspection of the wiring and connections is essential, looking for signs of wear or corrosion. Resistance testing should reveal values less than 5 ohms across connectors. - Frayed wires, corrosion at terminals, intermittent temperature readings.
- Thermostat Housing Removal: If the thermostat housing is not properly removed, it may obstruct access to the coolant temperature sensor. This can lead to delays in repairs and unnecessary labor costs. Proper tools, such as a torque wrench for the housing bolts (typically 89 lb-in), should be used during reinstallation. - Obstruction during service, improper sensor installation.
Diagnostic Steps
Professional Diagnosis Process
Follow these systematic steps to accurately diagnose the issue. Each step builds on the previous one to ensure accurate diagnosis.
- STEP 1 - Visual Inspection: Start with a thorough visual inspection of the coolant temperature sensor's wiring and connections. Look for any signs of corrosion or damage. Use a multimeter to check for continuity in the wiring harness, ensuring resistance is below 5 ohms. This step helps confirm if the issue is not related to wiring.
- STEP 2 - Sensor Testing: Test the coolant temperature sensor by measuring its resistance at various temperatures. The sensor should show approximately 2,500-3,000 ohms at 20°C, decreasing as the temperature rises. If the readings are erratic or outside the normal range, the sensor is likely faulty and requires replacement.
- STEP 3 - Accessing the Sensor: If the sensor is confirmed faulty, remove the intake manifold and coolant thermostat housing as per the manufacturer’s instructions. Use the correct tools to avoid damaging the components. Torque specifications for the thermostat housing bolts should be adhered to, typically around 89 lb-in.
- STEP 4 - Replacement and Testing: Replace the faulty coolant temperature sensor with a quality OEM part (for example, P/N 12625112 for GM vehicles). After installation, clear any diagnostic trouble codes using a scan tool, and check the system's operation by monitoring the temperature readings to ensure proper functionality.
