SPN 110 Suspect Parameter Number (SPN) and Failure Mode Indicator (FMI) Description SPN FMI Description Possible Causes 110 0 Engine Coolant Temperature Stuck thermostat Overheating Low coolant Cooling fan malfunction Skewed ECT Sensor 110 7 Engine Coolant Temperature Not Warm 110 16 Engine Coolant Temperature High Thermostat stuck open Cooling fan always ON High resistance in low reference circuit Skewed ECT Sensor Stuck thermostat Low coolant Cooling fan malfunction Skewed ECT Sensor Circuit Description The engine coolant temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. The engine control module (ECM) supplies 5 volts on the ECT signal circuit and supplies ground on the low reference circuit. During a cold start the ECM compares the ECT sensor, intake air temperature (IAT) sensor and mass air flow (MAF) temperature sensor values. All three values should closely match.
Conditions to Run SPN SPN 110 0 Engine Coolant Temperature Overheating Ignition is ON SPN 110-3 and 110-4 are not set SPN 110 7 Engine Coolant Temperature Not Warm SPN 110-3 and 110-4 are not set Engine speed is greater than 1500 RPM for 20 seconds The ECM requires a specific engine run time for a given engine start temperature. Refer to the table below for more information. Coolant Temp vs. Run Time Table ECT Startup Temp Engine Run Time -30 F (-34 C) 67 minutes -10 F (-23 C) 32 minutes 10 F (-12 C) 20 minutes 30 F (-1 C) 15 minutes 50 F (10 C) 7 minutes 65 F (18 C) 2 minutes SPN 110 16 Engine Coolant Temperature High Ignition is ON SPN 110-3 and 110-4 are not set
Conditions to Set SPN SPN 110 0 Engine Coolant Temperature Overheating The ECM detects that the ECT temperature is greater than 250F (121C) for greater than 1 second. SPN 110 7 Engine Coolant Temperature Not Warm The ECM detects that the ECT is less than 149F (65C) when the SPN 110-7 conditions to run are met. SPN 110 16 Engine Coolant Temperature High The ECM detects that the ECT temperature is greater than 250F (121C) for greater than 1 second. Action Taken When SPN Sets SPN 110 0 Engine Coolant Temperature Overheating The ECM will turn ON the check engine lamp (CEL) The ECM will turn ON the stop engine lamp (SEL) (If equipped) A buzzer will sound and an overheat message will displayed on the instrument cluster The Engine will operate in Reduced Power Mode 110-0 is a Type A SPN SPN 110 7 Engine Coolant Temperature Not Warm The ECM will turn ON the malfunction indicator light (MIL) 110-7 is a Type B SPN SPN 110 16 Engine Coolant Temperature High The ECM will turn ON the check engine lamp (CEL) The ECM will turn ON the stop engine lamp (SEL) (If equipped) A buzzer will sound and an overheat message will displayed on the instrument cluster The Engine will operate in Reduced Power Mode 110-16 is a Type A SPN
Diagnostic Reference Review Strategy Based Diagnosis for an overview of the diagnostic approach. Diagnostic Procedure Instructions provides an overview of each diagnostic category. Perform the Diagnostic System Check prior to using this diagnostic. Test for intermittent or poor connections. Review Schematics and Connector End Views to locate test points. Review the SPN Type, Indicator Lamp Definitions, and Conditions to Clear the SPN/Indicator Lamp. Diagnostic Tips After starting the engine, the ECT sensor temperature should rise steadily, and then stabilize after the thermostat opens. Test the ECT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor can result in a drivability condition. The following table illustrates the difference between temperature and resistance. Sensor resistance is measured with a DMM between sensor terminals A and B with sensor disconnected. ECT Sensor Table Temperature Sensor Resistance -40 F (-40 C) 101K Ω -4 F (-20 C) 29K Ω 32 F (0 C) 9.4K Ω 104 F (40 C) 1.5K Ω 176 F (80 C) 334 Ω 302 F (150 C) 47.5 Ω NOTE: Resistance values are approximate
Required Tools Terminal Test Probe Kit Fused Jumper Digital Multi-meter High Impedance Test Lamp Electronic Service Tool Circuit Diagnostics WARNING! To prevent bodily injury or death, stay away from hot engine surfaces and rotating engine components. IMPORTANT: If diagnosing SPN 110-2, vehicle must be OFF for a minimum of 8 hours. 1. Verify the engine coolant level, cooling fan operation, engine cooling system, and thermostat for proper operation. If a condition is found, repair as necessary. If no conditions are found, go to Step 2 2. Ignition OFF, disconnect the harness connector at the ECT sensor, test for less than 10 Ω between the low reference circuit terminal B and ground. If greater than 10 Ω, disconnect the ECM connector J1-B, test for less than 5 Ω between the ECT sensor connector low reference circuit terminal B and the ECM connector J1-B terminal D3. If 5 Ω or greater, repair the open or high resistance in the circuit. If less than 5 Ω, replace the ECM. If 10 Ω or less, go to Step 3 3. Ignition ON, verify the Electronic Service Tool Engine Coolant Temperature parameter displays less than -31F (-35C). If the Engine Coolant Temperature parameter is -31 F (-35 C) or greater, ignition OFF, disconnect the ECM connector J1-C, test for
infinite resistance between the ECT sensor signal circuit connector terminal A and ground. If not infinite resistance, repair the short to ground in the circuit. If infinite resistance, replace the ECM. If the Engine Coolant Temperature parameter is less than -31 F (-35 C), go to Step 4 Caution: If the fuse in the jumper wire opens, the signal circuit is shorted to voltage and the sensor may be damaged. 4. Install a 3 A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the Engine Coolant Temperature parameter is greater than 293 F (145 C). If the Engine Coolant Temperature parameter is 293 F (145 C) or less, ignition OFF, remove fused jumper wire, disconnect the ECM connector J1-C, test for less than 1 V between the ECT sensor connector signal circuit terminal A and ground. If 1 V or greater, repair the short to voltage in the circuit. If less than 1 V, test for less than 5 Ω between the ECT sensor connector signal circuit terminal B and the ECM connector J1-C terminal F2. If greater than 5 Ω, repair the open or high resistance in the circuit. If less than 5 Ω, replace the ECM. If the Engine Coolant Temperature parameter is greater than 293 F (145 C), replace the ECT sensor.