P0116 on 2007-2009 Saturn Aura 2.4L: Engine Temperature Performance Causes and Fixes

What's Unique About the 2007-2009 Saturn Aura

The 2.4L Ecotec engine used in the Saturn Aura was also used in many other GM vehicles like the Chevrolet Malibu, Pontiac G6, and Chevrolet HHR. Across all these 🎬 Watch: Step-by-step thermostat replacement on the 2.4L Ecotec engine. platforms, this engine family has a well-documented, high-frequency failure of the engine thermostat sticking in the open position. The rubber seal on the thermostat is known to degrade and break apart, jamming the valve open. While the code points to a sensor performance issue, the root cause is very frequently this mechanical thermostat failure, making it the primary suspect by a wide margin over an actual sensor fault.

Symptoms You May Notice

• Check Engine Light is on
• Engine temperature gauge reads lower than normal, drops to 'C' or '---', or stops working entirely.
• Heater blows cool or only lukewarm air, especially at idle
• Cooling fans run constantly at high speed, even when the engine is cold.
• Noticeable decrease in fuel economy
• Engine takes an unusually long time to warm up
• A/C system may be disabled by the PCM.

Most Likely Causes

1. Engine Thermostat Stuck Open 🔴 High Probability → Shop Integrated Thermostat Housing Assembly The thermostat assembly on the 2.4L Ecotec engine is a known high-failure part. The rubber seal degrades over time, breaks apart, and jams the thermostat in the open position, a common issue across all GM platforms using this engine.
   How to confirm: Use a scan tool to monitor live engine coolant temperature. If the engine fails to reach and maintain operating temperature (typically 180-195°F) after 10-15 minutes of driving, the thermostat is likely stuck open. The temperature may also drop significantly at highway speeds. Another strong symptom is the heater not blowing hot air.
   Typical fix: Replace the engine thermostat and its seal/housing assembly. On the 2.4L LE5, the thermostat is located on the driver's side of the engine, behind the exhaust manifold heat shield, making access somewhat difficult. It is crucial to bleed the cooling system of air after the replacement.
   Est. part cost: $25-$80
2. Faulty Engine Coolant Temperature (ECT) Sensor 🟡 Medium Probability → Shop Engine Coolant Temperature Sensor
   How to confirm: On a cold engine (after sitting overnight), use a scan tool to compare the ECT and Intake Air Temperature (IAT) readings. They should be within a few degrees of each other. If the ECT reading is illogical (e.g., -40°F or 250°F), the sensor is bad.
   Typical fix: Replace the ECT sensor. Since it 🎬 See how to replace the engine coolant temperature sensor. is located near the thermostat housing, it is often wise to replace it at the same time as the thermostat. The repair involves draining some coolant, disconnecting the electrical connector, and unscrewing the sensor.
   Est. part cost: $15-$40
3. Low Engine Coolant Level ⚪ Low Probability → Shop Engine Coolant / Antifreeze
   How to confirm: Visually inspect the coolant level in the overflow reservoir when the engine is cold. If it is low, inspect the system for leaks. An air pocket in the system from a low coolant level can prevent the ECT sensor from reading the coolant temperature correctly, causing erratic readings.
   Typical fix: Top off the cooling system with DEX-COOL approved coolant and bleed any air from the system. Find and repair the source of any leaks.
   Est. part cost: $15-$25

Rare But Worth Checking

• Wiring or Connector Issue: The wiring harness to the ECT sensor can become damaged, chafed, or corroded, causing an intermittent or lost signal. Wiggling the connector while monitoring live data on a scan tool can help identify a bad connection. Check the connector and wiring for breaks or corrosion before replacing parts.
• Cooling Fan Relay Stuck On: If a cooling fan relay fails in the 'on' position, the fans will run constantly from startup. This can over-cool the engine, significantly increasing warm-up time and potentially triggering a P0116, similar to a stuck-open thermostat.

Diagnosis Steps

1. Check for other DTCs: Use an OBD-II scanner to see if any other codes are present, especially P0128, P0117, or P0118. The presence of P0128 strongly suggests a thermostat issue.
2. Inspect Coolant Level: With the engine cold, check the coolant level in the reservoir. Ensure it is at the 'Full Cold' line. A low level can cause this code.
3. Cold Soak Sensor Check: After the car has sat overnight, turn the key to the 'On' position (without starting the engine). Use a scan tool to compare the Engine Coolant Temperature (ECT) and Intake Air Temperature (IAT) readings. They should be nearly identical. If the ECT reading is drastically different, the sensor or its wiring is likely faulty.
4. Monitor Engine Warm-Up: Start the engine and use the scan tool to watch the live ECT data. The temperature should rise steadily. Drive the vehicle and observe if the temperature reaches and holds around 180°F or higher (typically 195-210°F is normal). If it takes a very long time to warm up or the temperature drops significantly at highway speeds, the thermostat is almost certainly stuck open.
5. Inspect Wiring: If the sensor readings are erratic or illogical (e.g., jumping between -40°F and 250°F), visually inspect the ECT sensor's connector and wiring for any signs of damage, corrosion, or loose connections.
6. Test the Thermostat (if necessary): If diagnostics are inconclusive, the thermostat can be removed and tested by placing it in a pot of water with a thermometer and heating it to observe its opening temperature. However, given the high failure rate, replacement is often done based on the warm-up test alone.

Parts You'll Likely Need

• Engine Coolant Thermostat (OEM #12622410) — This is the most common failure point for code P0116 on the 2.4L Ecotec engine. The original part is prone to sticking open, preventing the engine from reaching operating temperature. Using the OEM ACDelco part is highly recommended to prevent premature failure of aftermarket alternatives.
  Trusted brands: ACDelco (131-158), Motorad, Gates
  OEM price range: $50-$80
  Aftermarket price range: $25-$50
• Engine Coolant Temperature (ECT) Sensor (OEM #213-4514) — This is the second most likely cause. The sensor can fail and send inaccurate or erratic temperature readings to the computer. It's a relatively inexpensive part to replace alongside the thermostat.
  Trusted brands: ACDelco, NTK, Delphi
  OEM price range: $25-$45
  Aftermarket price range: $15-$30
• DEX-COOL Engine Coolant/Antifreeze — The cooling system will need to be drained and refilled when replacing the thermostat or sensor. A 50/50 mix with distilled water is required.
  Trusted brands: ACDelco, Prestone
  OEM price range: $20-$25 per gallon
  Aftermarket price range: $18-$22 per gallon

Related Codes That Often Appear With This One

• P0128 — P0128 (Coolant Temperature Below Thermostat Regulating Temperature) is triggered by the exact same condition: the engine not warming up properly. P0116 is a performance check, while P0128 is a rationality check against the thermostat's expected opening temperature. They often appear together for a stuck-open thermostat and result in the same symptoms.
🎬 Watch: A mechanic explains the P0128 code and thermostat failure.

Platform-Specific Known Issues

• Thermostat Location and Access: → Shop Integrated Thermostat Housing Assembly On the 2.4L LE5 engine, the thermostat housing is located on the driver's side of the engine, bolted to the cylinder head. Access is partially obstructed by the exhaust manifold and its heat shield, as well as heater hoses. Some repair videos show mechanics working from both the top and bottom of the vehicle to access the bolts and hoses.

Mechanic-Grade Diagnostic Values

• ECT Sensor Resistance (Cold Engine) — expected: 2,000 - 3,000 Ohms at 68°F (20°C).. Failure: A reading significantly outside this range, or an open/short circuit (OL), indicates a faulty sensor.
• ECT Sensor Resistance (Hot Engine) — expected: 200 - 300 Ohms at ~194-212°F (90-100°C).. Failure: Resistance fails to drop into this range as the engine warms up, pointing to a bad sensor.
• ECT Sensor Signal Voltage (Key On, Engine Off, Cold) — expected: ~2.0V - 3.0V.. Failure: Voltage is stuck near 5V (open circuit) or 0V (short circuit), indicating a wiring or sensor fault.
• ECT Sensor Signal Voltage (Engine at Operating Temp) — expected: ~0.5V.. Failure: Voltage remains high (e.g., >1.5V) after the engine has warmed up, indicating the PCM is not seeing the temperature increase. This is a classic symptom of a stuck-open thermostat.

Scan Tool Commands That Help

• Tech2 / GDS2 or equivalent professional scan tool: Cooling Fan Relay Command — If the cooling fans are running constantly, use this bidirectional command to attempt to turn them off. If the fans do not shut off when commanded, it points to a stuck relay or a short to power in the fan control circuit, which could be the cause of the over-cooling and the P0116 code.

Wiring & Ground Locations

• G105 — On the left rear of the engine block.. This is a primary engine block ground. A poor connection here can cause floating ground issues for sensors mounted to the engine, including the ECT, leading to erratic readings.
• G106 — On the rear of the engine, near the Park/Neutral Position (PNP) switch for the 2.4L (VIN 5).. Another key engine ground. Verifying this ground is clean and tight is essential when diagnosing any electrical sensor issue on the engine.
• G110 — On the top rear of the engine for the 2.4L (VIN 5).. This ground point's integrity is crucial for the proper operation of the engine control system and its sensors.
• ECT Sensor Connector — On the ECT sensor, which is located on the right side of the engine, below the exhaust camshaft position sensor.. This is the direct connection point. Check for corrosion, pin fitment, and wire damage here. The two wires are a 5-volt reference and a low reference (signal return) to the ECM.
• Engine Control Module (ECM) — Located on the left side of the engine compartment, behind the battery.. All sensor wiring terminates here. A visual inspection for corrosion at the ECM connectors is a valid last step if wiring issues are suspected.

Real Owner Repair Stories

• Multiple forum and YouTube reports, summarized from a P0128 diagnostic article for the same engine. (Chevy Equinox / GMC Terrain with 2.4L Ecotec engine) — Check Engine Light with code P0128 (sister code to P0116) returned shortly after a repair.
  ❌ Tried (didn't work) Replacing the thermostat and coolant.
  ✅ What actually fixed it The cooling system was not properly bled ('burped') after the thermostat replacement. An air pocket was trapped near the ECT sensor, causing it to read the temperature of the air, not the coolant, which triggered the code again. The final fix was to properly bleed all air from the cooling system.
• Reddit user in r/MechanicAdvice, summarized from a P0128 diagnostic article for the same engine. (Vehicle with 2.4L Ecotec engine) — Check Engine Light with P0128 came on, was fixed, and then returned two months later.
  ❌ Tried (didn't work) Replacing the thermostat with a standard aftermarket part from a local auto parts store.
  ✅ What actually fixed it The aftermarket thermostat was presumed to be faulty or of the incorrect temperature specification. The final recommended fix was to replace the thermostat again, this time using a genuine OEM ACDelco part (12622410) to ensure it regulated at the precise temperature required by the ECM.

OEM Part Supersession History

• 90537453, 55350941, 21018811, 12615097 → 12622410 — Part consolidation and potential design updates over the long production run of the Ecotec engine family.
  Heads up: The newest part number, 12622410, is the correct replacement for all previous versions for this application. Using old stock or a number from the superseded list is not recommended.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Timing Chain Stretch / Guide Failure 🟠 Medium — Becomes a concern over 100,000 miles, especially if oil changes are neglected. The 2.4L Ecotec is less notorious for this than the 3.6L V6, but failure of the tensioner or plastic guides can still occur.
• Excessive Oil Consumption 🟠 Medium — Common on 2.4L Ecotec engines, often attributed to piston ring design. Can lead to low oil levels that damage VVT components and timing chains if not monitored closely. (Ref: While no specific recall for the Aura, this was a known issue across the Ecotec engine family.)
• Sudden Loss of Electric Power Steering (EPS) 🔴 High — Widespread enough to trigger a major safety recall. Can happen at any mileage. (Ref: Recall NHTSA 14V153000 / GM N140115. Affects 2008-2009 models. Dealers were to replace the torque sensor assembly and/or EPS motor controller.)
• Fractured Transmission Shift Cable 🟠 Medium — Common failure on vehicles with the 4-speed automatic transmission (4T45-E). The tabs on the cable end break, preventing gear selection. (Ref: Recall NHTSA 12V460000. Affects 2007-2010 models with the 4-speed automatic.)
• Camshaft Position Actuator Solenoid Failure 🟡 Low — Very common failure item, often occurring after 60,000 miles. Clogging of solenoid screens by oil sludge is a primary cause. Leads to codes like P0010, P0011, P0013, P0014.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For this specific repair, using used parts is not recommended. The primary failure components (thermostat, sensor) are wear items with a finite lifespan and are inexpensive to buy new.

What to inspect on the donor part:

• Not applicable for this repair.

OEM-only on this vehicle (don't cheap out):

• Engine Coolant Thermostat: Forum and technician consensus strongly advises using the OEM ACDelco thermostat (PN 12622410). Aftermarket thermostats for this engine are known to have high rates of premature failure or incorrect temperature ratings, often causing the same code to return within months.

Aftermarket brands forum-validated for this vehicle:

• ECT Sensor: NTK, Delphi, ACDelco (OEM)

Brands owners have reported issues with on this vehicle:

• Thermostat: Avoid generic, 'white-box', or store-brand thermostats (e.g., Failsafe, as some reviews show issues). The cost savings are minimal compared to the risk of repeat labor.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0128 — This code frequently appears with P0116 on the Aura; it specifically indicates the engine is not reaching operating temperature fast enough, often due to a stuck-open thermostat.
• P0117 — A companion code related to the Engine Coolant Temperature (ECT) sensor circuit, which should be checked if P0116 is present.
• P0118 — Another ECT sensor circuit code that may trigger alongside P0116 if the sensor or its wiring is faulty.
• P0010 — Related to the failure of the Camshaft Position Actuator Solenoids, a very common issue on the 2.4L LE5 engine often caused by oil sludge.
• P0011 — An intake camshaft position timing code that often occurs alongside solenoid failure on this engine platform.
• P0013 — Exhaust camshaft actuator circuit code, frequently seen on the 2.4L Ecotec due to solenoid screen clogging.
• P0014 — Exhaust camshaft timing over-advanced code, part of the common VVT solenoid failure suite on this vehicle.

Frequently Asked Questions