How to Fix Diagnostic Code P1115

by

🚨 Diagnostic Profile

Vehicle Make: Chrysler

Description: Engine Coolant Temperature (ECT) Sensor Circuit Intermittent High Voltage. The powertrain control module (PCM) has detected a signal voltage on the ECT sensor circuit that is above the expected range, and the fault is not continuously present. Typical causes include intermittent open or high-resistance connections, corroded or loose terminals at the sensor connector, chafed or shorted harness wiring, or a failing sensor element.

🚨 Repair Difficulty Tier

Tier: [Intermediate]

Diagnosis requires a digital multimeter, scan tool with live data, and familiarity with reading circuit voltage and resistance. Sensor replacement is typically straightforward, but intermittent faults often require wiggle testing and harness inspection to locate the actual fault.

🛠️ Resolution Steps

Step 1: Preliminary Inspection

  • Verify battery voltage is at least 12.4V at rest and charging system output is within the standard 13.5–14.7V range at idle with accessories off, using a digital multimeter at the battery terminals.
  • Review freeze frame data and confirm DTC status (current vs. history) on the scan tool; note engine run time, coolant temp, and load conditions at the time the fault was set (commonly stored as a P0118 high-voltage ECT circuit code on Chrysler PCM strategy).
  • Visually inspect the ECT sensor connector for corrosion, bent pins, moisture intrusion, or a partially seated locking tab. On most Chrysler 3.6L, 2.4L, and 5.7L applications the ECT sensor is threaded into the thermostat housing or cylinder head near the upper radiator hose outlet — confirm exact location against the engine-specific service manual for the vehicle in question.
  • Inspect the harness routing near the sensor for chafing, pinching against the alternator or accessory bracket, heat damage from exhaust proximity, or aftermarket modifications.
  • Check the coolant level and condition, as low coolant or air pockets in the cooling system can cause erratic ECT readings and intermittent high-voltage faults.

Step 2: Diagnostic Verification

  • Monitor ECT sensor live data (PID: Engine Coolant Temp) with the engine cold and again after reaching operating temperature (~195–220°F); compare the scan tool reading against a calibrated infrared thermometer or known-good reference at the thermostat housing.
  • Measure reference voltage on the ECT signal circuit with the key on, engine off (KOEO) — the PCM typically applies a 5V reference through a pull-up resistor; confirm the signal reads near 5V when the sensor is disconnected (open circuit = high voltage, consistent with the fault description).
  • Measure sensor resistance directly at the ECT sensor connector (engine cold, ambient ~70°F) using an ohmmeter and compare to a standard NTC thermistor curve (typically several thousand ohms cold, dropping to a few hundred ohms at full operating temperature); refer to the factory coolant temp-vs-resistance chart for the exact engine family.
  • Perform a wiggle test on the harness and connector while monitoring live ECT data and watching for voltage spikes toward 5V (open) or drops toward 0V (short), working from the sensor connector back toward the PCM harness connector.
  • Check the signal and ground return circuits for continuity and excessive resistance (should read close to 0 ohms) between the sensor connector and the corresponding PCM connector pins; consult the vehicle-specific factory wiring diagram to confirm exact pin locations and wire colors, as these vary by model year and engine.
  • With the sensor connector disconnected, check for unwanted voltage or a short to power on the signal circuit (should read near 0V with key on, engine off if no short is present) and verify no short to chassis ground.
  • Review applicable Chrysler/FCA/Stellantis technical service bulletins and check for open PCM reflash campaigns related to ECT circuit diagnostic trouble codes for the specific model year and engine combination.

Step 3: Resolution & Reset Process

  • Repair or replace the faulty component: perform a harness repair using OEM-spec wire and heat-shrink soldered splices, service corroded terminals with new pins, or replace the ECT sensor outright if resistance values fall outside specification or the sensor fails the wiggle test.
  • Confirm the replacement sensor is torqued to spec (typically 10–15 ft-lbs depending on application — verify against the specific engine’s service manual) and that the connector locking tab is fully seated; apply dielectric grease to the terminal cavities to prevent future corrosion.
  • Clear stored DTCs with a scan tool and verify the repair by completing a drive cycle that cycles the engine from cold start through full operating temperature, allowing the thermostat monitor and related PCM strategies to run.
  • Confirm no pending or history codes return after at least two full drive cycles, and that live ECT data tracks smoothly and consistently with no voltage spikes during a secondary wiggle test.

📦 Parts, Labor, and Budget Estimates

Required Components/Software:

  • ECT sensor: OEM or OE-equivalent Mopar sensor specific to engine family (e.g., 3.6L Pentastar, 2.4L Tigershark, 5.7L HEMI) — verify exact part number by VIN at a dealer parts counter or OEM parts catalog.
  • Connector pigtail or terminal repair kit (if required) — Mopar/Metri-Pack style repair kit matched to connector type.
  • Dielectric grease and standard automotive wire repair supplies (heat-shrink butt connectors, solder, loom tape).
  • Scan tool capable of bidirectional PCM communication and live data streaming (factory-level tool such as Chrysler wiTECH preferred for PCM reflash or calibration updates, if a related TSB applies).

Average Component Price:

  • ECT sensor: approximately $15–$55 for the part (OEM Mopar sensors typically run higher than aftermarket equivalents).
  • Connector/terminal repair kit or pigtail: approximately $20–$60.
  • Coolant top-off or full system flush (if air/contamination is found): approximately $15–$150 depending on coolant type and whether a full flush is performed.
  • wiTECH dealer programming session (if a PCM reflash TSB applies): approximately $100–$200 flat fee at a dealership, in addition to diagnostic labor.

Estimated Labor Hours:

  • Diagnosis and verification (including wiggle test and circuit checks): 0.5–1.5 hours shop book time, more if intermittent fault requires extended road testing.
  • Sensor replacement: typically 0.3–0.7 hours; harness/connector repair: 0.5–1.5 hours depending on accessibility and whether intake or other components must be removed for access.
  • Verification drive cycle, DTC clear, and final data confirmation: 0.2–0.5 hours.