🚨 Diagnostic Profile
Vehicle Make: Chrysler
Fault Description: Engine Coolant Temperature (ECT) Signal Out-Of-Range High. The Powertrain Control Module (PCM) is reading an ECT sensor voltage or resistance above the expected operating range, which typically indicates an open circuit, high resistance in the signal or ground circuit, a failed sensor, or a connector fault.
Vehicle Variables: Gasoline, V6 or I4 (verify exact engine code on build sheet/VIN) | Model year confirmation required via VIN decode | DTC consistent with P0118 (ECT Circuit High Input) family
🚨 Repair Difficulty Tier
Tier: Intermediate
Sensor replacement is straightforward, but confirming whether the fault is in the sensor, the wiring harness, or the PCM requires live data analysis, circuit testing, and familiarity with the vehicle’s service information.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
- Verify the stored DTC and freeze frame data with a factory-level scan tool (such as a Chrysler-compatible wiTECH-equivalent or a quality aftermarket scanner with enhanced PCM data access).
- Check engine coolant level and condition. Confirm the cooling system has been bled of air and the thermostat is opening/closing at its rated temperature.
- Visually inspect the ECT sensor connector, typically located on the cylinder head, thermostat housing, or front engine block near the upper radiator hose, for corrosion, bent pins, moisture intrusion, or a loose/unseated connector lock.
- Inspect the harness routing near the sensor for chafing against the engine block, heat damage near exhaust components, or pinched wires from prior service work.
- Check for related codes such as cooling fan control faults, thermostat circuit codes, or low coolant level warnings that may point to a shared root cause.
Step 2: Diagnostic Verification
- Compare live ECT data on the scan tool against actual engine temperature using an infrared thermometer aimed at the thermostat housing. Note any mismatch at cold start and after the engine reaches normal operating temperature.
- With the key on, engine off, and the ECT connector disconnected, measure the sensor reference voltage at the harness-side connector using a digital multimeter against a known good chassis or engine ground. Expect to see the PCM’s standard 5-volt reference signal; a reading at or near 5V with the sensor disconnected is normal and confirms the circuit is intact, while 0V indicates an open reference circuit.
- With the sensor disconnected, check the signal circuit for continuity and resistance back to the PCM connector. Resistance should read near 0 ohms (negligible) on a good circuit; any significant resistance indicates a corroded splice, damaged wire, or poor connector terminal.
- Check the sensor ground circuit for voltage drop under load by backprobing with the engine running and the sensor connected. A voltage drop exceeding roughly 0.1V typically indicates a poor ground connection requiring further tracing.
- Measure sensor resistance directly across its two terminals at a known ambient temperature using an ohmmeter, then compare the reading against the OEM temperature-to-resistance chart found in the factory service manual for this specific engine family; most Chrysler ECT sensors read in the tens of thousands of ohms when cold and drop to a few hundred ohms near full operating temperature.
- With the connector disconnected, check for unwanted shorts to battery voltage or to ground on the signal circuit using a multimeter, as a short to voltage is a common cause of an out-of-range-high code.
Step 3: Resolution & Reset Process
- If the sensor reads outside the OEM resistance specification or fails the voltage tests, replace the ECT sensor. Clean the sealing surface, apply the OEM-specified thread sealant if required (do not use excess Teflon tape, which can insulate the ground path), and torque to the factory specification listed in the service manual (commonly in the 7 to 11 lb-ft range for threaded coolant sensors, but verify against the specific engine’s service data before installation).
- If the wiring tests faulty, repair the affected circuit using OEM-approved solder-and-heat-shrink or crimp-and-seal splice methods rated for engine bay environments, then retest the circuit before buttoning up the harness.
- If the sensor and wiring both test within specification but the PCM continues to read incorrectly, check for applicable Technical Service Bulletins (TSBs) addressing PCM software calibration updates for ECT circuit logic, and consider PCM reflash or replacement only after all other causes are ruled out.
- Clear the DTC using the scan tool, then perform a drive cycle consisting of a cold start, idle warm-up to operating temperature, and varied-load highway driving as outlined in the vehicle’s OEM drive cycle procedure to allow the PCM to run its ECT rationality monitor.
- Confirm the fault does not return and that live ECT data tracks a smooth, consistent rise from ambient temperature at cold start up to normal operating temperature (typically stabilizing in the 195-220°F range) with no erratic jumps or flatlines.
📦 Parts, Labor, and Budget Estimates
Required Components/Software:
- ECT sensor: OEM or OE-equivalent sensor specific to engine family; verify exact part number via VIN at dealer parts counter or parts catalog before ordering
- Connector repair kit or wiring repair materials, if required: weatherproof splice connectors, heat-shrink tubing, and OEM-style pigtail connector if the original connector is damaged
- Coolant (if drained): OEM-specified coolant type (commonly a 5-year/100,000-mile HOAT formula for most Chrysler products from the 2001+ model years); verify exact spec and capacity for the specific engine before refilling
- PCM software update, if applicable: dealer-level reflash using the latest calibration available through Chrysler’s authorized diagnostic system, cost varies by dealer
Average Component Price:
- ECT sensor: approximately $15 to $60 for the part (OEM sensors trend toward the higher end of this range)
- Wiring or connector repair supplies: approximately $10 to $40 depending on whether a full pigtail connector is needed versus basic splice supplies
- Coolant: approximately $15 to $30 per gallon for OEM-spec coolant, with most jobs requiring 1 to 2 gallons depending on dilution ratio
Estimated Labor Hours:
- Diagnosis and verification: approximately 0.5 to 1.0 hour, dependent on accessibility and whether a lift is required to reach the sensor
- Sensor replacement: approximately 0.3 to 0.8 hour, higher if the sensor is positioned under intake components or requires partial coolant draining
- Wiring repair, if required: approximately 0.5 to 1.5 hours depending on the location and extent of harness damage
- Verification drive cycle and reset: approximately 0.3 to 0.5 hour, plus potential additional time if a road test is needed to confirm full drive cycle completion
- Dealer PCM reflash labor (if applicable): approximately 0.5 to 1.0 hour, billed separately from sensor diagnostic labor