Technical Definition:

Insufficient Coolant Temperature for Closed Loop Fuel Control

Technical Description:

Possible Causes:

Possible Symptoms:

Insufficient Coolant Temperature for Closed Loop Fuel Control

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Low engine coolant level
– Leaking or stuck open thermostat
– Faulty Engine Coolant Temperature (ECT) sensor
– Engine Coolant Temperature (ECT) sensor harness is open or shorted
– Engine Coolant Temperature (ECT) sensor electrical circuit poor connection

Specific Makes:

Technical Definition:

Throttle / Pedal Position Sensor / Switch A Circuit Malfunction

Technical Description:

Possible Causes:

Possible Symptoms:

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

Specific Makes:

Technical Definition:

Engine Coolant Temperature (ECT) (Sensor 1) Circuit Range / Performance

Technical Description:

The ECT (Engine coolant temperature) sensor is a thermistor which changes resistance based on temperature of the coolant in contact with it. The ECT sensor will be located in the block or coolant passage. Usually it is a two wire sensor. One wire is a 5 Volt supply from the PCM (Powertrain Control Module) to the ECT. The other is a ground to the ECT.

Possible Causes:

• Missing or stuck-open thermostat
• Bad ECT sensor
• Short or open on signal wire
• Short or open on ground wire
• Poor connections in wiring

Possible Symptoms:

• MIL (Malfunction Indicator Lamp) illumination
• Poor drivability
• Black smoke at tailpipe
• Poor fuel economy
• May not idle
• May exhibit stalling or misfires

Engine Coolant Temperature Circuit Range/Performance Problem

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Low engine coolant level
– Faulty Engine Coolant Temperature (ECT) sensor
– Faulty engine coolant thermostat
– Engine Coolant Temperature (ECT) sensor harness is open or shorted
– Engine Coolant Temperature (ECT) sensor circuit poor electrical connection

Specific Makes:

Technical Definition:

Engine Coolant Temperature (ECT) (Sensor 1) Circuit Low

Technical Description:

The ECT (Engine coolant temperature) sensor is a thermistor located in the engine block or other coolant passage. It changes resistance with changes in temperature of the coolant that it’s in contact with. It’s usually a two wire sensor. One wire is a 5 volt reference from PCM (Powertrain Control Module) and the other is a ground supplied from PCM.

Possible Causes:

• Bad ECT sensor
• Short to ground on ECT signal circuit
• Faulty or damaged connectors
• Wiring harness damaged
• Loose terminals at ECT or PCM
• POSSIBLY an overheated engine
• Bad PCM

Possible Symptoms:

• MIL (Malfunction Indicator Lamp) illumination
• Poor fuel economy
• Poor drivability
• Engine may run rough or blow black smoke out the tailpipe
• May not idle
• May start and then die

Engine Coolant Temperature Circuit Low Input

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Low engine coolant level
– Faulty Engine Coolant Temperature (ECT) sensor
– Faulty engine coolant thermostat
– Engine Coolant Temperature (ECT) sensor harness is open or shorted
– Engine Coolant Temperature (ECT) sensor circuit poor electrical connection

Specific Makes:

Technical Definition:

Engine Coolant Temperature (ECT) (Sensor 1) Circuit High

Technical Description:

The engine coolant temperature (ECT) sensor is a thermistor screwed into a coolant passage in the cylinder head. Sensor resistance is high when coolant temperature is low and resistance drops when coolant temperature increases.

Possible Causes:

• A bad connection at the sensor
• An open in the ground circuit between the ECT sensor and the PCM
• A short in the voltage feed between the sensor and the PCM
• A bad PCM (less likely)
• A bad temperature sensor (shorted internally)

Possible Symptoms:

Engine Coolant Temperature Circuit High Input

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Low engine coolant level
– Faulty Engine Coolant Temperature (ECT) sensor
– Faulty engine coolant thermostat
– Engine Coolant Temperature (ECT) sensor harness is open or shorted
– Engine Coolant Temperature (ECT) sensor electrical circuit poor connection

Specific Makes:

Technical Definition:

Engine Coolant Temperature (ECT) (Sensor 1) Circuit Intermittent

Technical Description:

Possible Causes:

Possible Symptoms:

Engine Coolant Temperature Circuit Intermittent

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Low engine coolant level
– Faulty Engine Coolant Temperature (ECT) sensor
– Faulty engine coolant thermostat
– Engine Coolant Temperature (ECT) sensor harness is open or shorted
– Engine Coolant Temperature (ECT) sensor electrical circuit poor connection

Specific Makes:

Technical Definition:

Engine Coolant Temperature (ECT) (Sensor 1) Circuit

Technical Description:

The ECT (Engine coolant temperature) sensor is basically a thermistor that changes resistance with temperature. Usually a two wire sensor, a 5Volt reference from PCM (Powertrain Control Module) and ground signal to PCM. This is different from a temperature SENDER (which usually operates the dash temperature gauge and operates in a similar way as the SENSOR, only it’s a different circuit than what a P0115 is referring to). As the temperature of the coolant changes, the resistance changes on the ground signal to the PCM. When the engine is cold, the resistance is high. When the engine is warm, the resistance is low. If the PCM detects a voltage condition that seems abnormally low or high,P0115 will set.

Possible Causes:

• Wiring or connector damaged at sensor
• Open or short in reference or signal circuit
• Open or short in signal circuit
• Bad PCM

Possible Symptoms:

• MIL (Malfunction Indicator Lamp) illumination will always occur
• Vehicle may be hard to start
• May blow a lot of black smoke and run extremely rich
• Engine may want to die or backfire in tailpipe
• Engine may run lean and increased Nox emissions may be apparent (Requires gas analyzer)
• Cooling fans may run all the time when they shouldn’t be, or not at all when they should be

Engine Coolant Temperature Circuit Malfunction

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Low engine coolant level
– Faulty Engine Coolant Temperature (ECT) sensor
– Faulty engine coolant thermostat
– Engine Coolant Temperature (ECT) sensor harness is open or shorted
– Engine Coolant Temperature (ECT) sensor circuit poor electrical connection

Specific Makes:

Technical Definition:

Intake Air Temperature (Sensor 1) Circuit Range / Performance

Technical Description:

Possible Causes:

Possible Symptoms:

Intake Air Temperature Circuit Range/Performance Problem

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Intake Air Temperature (IAT) sensor
– Dirty air filter
– Intake Air Temperature (IAT) sensor harness is open or shorted
– Intake Air Temperature (IAT) sensor circuit poor electrical connection

Specific Makes:

Technical Definition:

Intake Air Temperature (Sensor 1) Circuit Low

Technical Description:

Possible Causes:

Possible Symptoms:

Intake Air Temperature Circuit Low Input

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Intake Air Temperature (IAT) sensor
– Dirty air filter
– Intake Air Temperature (IAT) sensor harness is open or shorted
– Intake Air Temperature (IAT) sensor circuit poor electrical connection

Specific Makes:

Technical Definition:

Intake Air Temperature (Sensor 1) Circuit High

Technical Description:

Possible Causes:

Possible Symptoms:

Intake Air Temperature Circuit High Input

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Intake Air Temperature (IAT) sensor
– Dirty air filter
– Intake Air Temperature (IAT) sensor harness is open or shorted
– Intake Air Temperature (IAT) sensor circuit poor electrical connection

Specific Makes:

Technical Definition:

Intake Air Temperature (Sensor 1) Circuit Intermittent

Technical Description:

Possible Causes:

Possible Symptoms:

Intake Air Temperature Circuit Intermittent

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Intake Air Temperature (IAT) sensor
– Dirty air filter
– Intake Air Temperature (IAT) sensor harness is open or shorted
– Intake Air Temperature (IAT) sensor circuit poor electrical connection

Specific Makes:

Technical Definition:

Intake Air Temperature (Sensor 1) Circuit

Technical Description:

Possible Causes:

Possible Symptoms:

Intake Air Temperature Circuit Malfunction

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Intake Air Temperature (IAT) sensor
– Dirty air filter
– Intake Air Temperature (IAT) sensor harness is open or shorted
– Intake Air Temperature (IAT) sensor circuit poor electrical connection

Specific Makes: