Code P0115 Check Engine light on, fan runs continuously at high speed

any suggested fixes for this problem? Yeah , view a wiring diagram to see what all is involved in turning on the cooling fans an test with a DVOM - digital volt ohmmeter . Free wiring diagrams here http://www.bbbind.com/free-tsb/ Enter vehicle info. year make ,model an engine . Under system click on engine , then under subsystem click on cooling fans. Click the search button then the blue link . Looking at the diagram i see three relay's - fan control , high fan control , lo fan control . All three relay's are commanded on by ther PCM - engine computer . Checking for DTC'S - diagnostic trouble code's with a scan tool . Double check your work - pinched wiring etc...... check for high speed fan relay stuck contacts .

Has two relays fan hi an fan low . did you see that ? ECT sensor - engine coolant temp sensor is a input to the ECM - engine control module . The ECM monitors the coolant temp . when the temp reaches a set temp. the ECM will energize the fan on low speed by suppling a ground .If the sensor ECT was bad would have a check engine light on an a codes set. Your best bet would be to have a qualified repair shop check it out .Hook up a scan tool .

The PCM regulates voltage to the coolant fan relays, which operate the fans. Refer to Engine Controls.

Engine Cooling Fan Description - Electric
The electric cooling fans are used to lower the temperature of the engine coolant flowing through the radiator. They are also used to cool the refrigerant (R-134a) flowing through the A/C condenser.
Operation
The electric cooling fan operates when the engine cooling temperature exceeds a certain value. The cooling fan on this engine is controlled by the PCM. The cooling fan has one speed. The PCM turns the cooling fan ON by grounding the coil of the cooling fan relay when certain conditions are met. When the A/C is requested, the cooling fan will also be turned ON.
Power for the cooling fan motors are supplied through Cool Fan #1 and Cool Fan #2 relays. The cooling fan relays are energized when current flows from the fuses in the Cell 23: Cooling Fan Controls , and through the relay coils to ground through the PCM. The Low Speed fans control circuit is grounded for low speed fans operation. During low speed fans operation, both fans run at a slow speed. The High Speed fans control circuit is grounded for high speed operation. During high speed fans operation, both fans run at high speed.
Important: When certain Diagnostic Trouble Codes (DTCs) are present, the PCM may command the cooling fans to run all the time. It is important to perform Powertrain On Board Diagnostic (OBD) System Check prior to diagnosing the engine cooling fans.
If a problem that involves the low speed cooling fan relay control circuit exists, DTC P0480 should set. If the problem affects the high speed cooling fan relay control circuit, DTC P0481 should set. A problem with the ECT sensor should set DTC P0117, P0118, P1114, or P1115. Any of these DTCs will affect cooling fan operation and should be diagnosed before using the Cooling Fan Diagnosis tables. The Cooling Fan Diagnosis tables should be used to diagnose the PCM controlled cooling fans only, if a DTC has not set.

The engine coolant temperature (ECT) sensor (3) is a thermistor, a resistor which changes value based on temperature, mounted in the engine coolant stream. Low coolant temperature produces a high resistance (100,000 ohms at -40°C) (-40°F), while high temperature causes low resistance (70 ohms at 130°C) (266°F).
The PCM supplies a 5 volt signal to the ECT sensor through a resistor in the PCM and monitors the terminal voltage. Since this forms a series circuit to ground through the ECT sensor, high sensor resistance (low temperature) will result in high PCM terminal voltage. When the resistance of the ECT sensor is low (high temperature), the terminal voltage will be drawn lower. This terminal voltage indicates engine coolant temperature to the PCM.
A hard fault in the ECT sensor circuit should set either a DTC P0117 or P0118. Remember, these DTCs indicate a malfunction in the engine coolant temperature circuit, so proper use of the DTC table may lead to either repairing a wiring problem or replacing the sensor, to properly repair a problem.

The engine coolant sensor is an input to the PCM , Two wire's both go to the PCM .An the PCM turns on the cooling fans !

DTC P0480 Cooling Fan Relay 1 Control Circuit
DTC P0481Cooling Fan Relay 2 Control Circuit
The Body Control Module (BCM) request the cooling fans. The BCM sends a Class 2 message to the PCM in order to enable the fans based on various inputs. Thebattery voltage travels to all three cooling fan relay coils. The PCM enables cooling fan relay #1 by providing the ground path. The PCM enables cooling fan relays #2 and mode control together by providing a ground path. The left and right cooling fans are connected in series. This will enable both fans on low speed when the fan #1 relay is energized. When all three fan relays are energized, both fans will operate at high speed. The high speed is possible because the fan relays are wired in a parallel circuit. When the PCM detects that certain DTCs are set, the PCM will enable the cooling fans.
The PCM will enable the engine cooling fans when certain Diagnostic Trouble Codes are set.

Important: A short to ground will cause an open fuse(s). Before performing this diagnostic procedure, inspect the fuse(s) for an open.
1
Did you perform the Instrument Cluster System Check?
--
Go to Step 2
Go to Instrument Cluster System Check
2
Turn the ignition switch to the ON position.
With the scan tool select Instrument Panel Cluster, Special Functions, Instrument Panel Cluster (IPC) gauges.
Perform the Coolant Gauge Sweep Test.
Does the coolant temperature gauge complete a full sweep when commanded?
--
Go to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls
Go to Step 3
3
Replace the instrument cluster. Refer to Instrument Cluster Replacement .
Did you complete the repair?
--
Go to Instrument Cluster System Check
--

Your best bet would be to take your vehicle to a qualified repair shop that knows how the system works . An has the tools to diagnose the problem .

code p 0442 refers to EVAP system so that is unlikely
check the fan operation and if you have a viscous fan hub ( fan clutch ) replace it
if you have electric fans , check coolant temperature sensor for operation , fuses , relay and fans
overheating is from low coolant levels , head gaskets/cracked heads, blocked radiator cores , fins flaking off core tubes, incorrect timing, blocked exhaust( cat converter)problem thermostat, over loading /over speeding, overdrive not engaging
if you over heating is predominately at lights , slow moving traffic or high engine rpms with low speed --check the fan operation and if it is viscous fan hub driven --replace the hub or if electric fans have that circuit checked out

P0116 - Engine Coolant Temperature (ECT) Circuit Range/Performance Problem
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.

As the temperature of the coolant changes the resistance on the signal wire changes accordingly. The PCM monitors the reading and determines coolant temperature in order to perform essential engine fuel management. When engine coolant is low, sensor resistance is high. The PCM will see a high signal voltage (low temperature). When coolant is warm, the sensor's resistance is low and the PCM will see a high temperature. The PCM expects to see slow resistance changes on the ECT signal circuit. If it sees a quick change in voltage that isn't consistent with an engine warming up, this P0116 code will set. Or if it sees a lack of change in ECT signal, this code may set.

Symptoms: There may be no noticeable symptoms if the problem is very intermittent, however the following may occur:
MIL (Malfunction Indicator Lamp) illumination
Poor drivability
Black smoke at tailpipe
Poor fuel economy
May not idle
May exhibit stalling or misfires

Causes: Potential causes of the P0116 code include:
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 Solutions: If there are any other ECT sensor codes, diagnose them first.
Using a scan tool, check the ECT reading. On a cold engine, it should match the IAT reading or should be equal to ambient (outside) temperature reading. If it does match the IAT or ambient temp, check the freeze frame data on your scan tool (if equipped). The saved data should tell you what the ECT reading was when the fault occurred.

a) If the saved info indicates that the engine coolant reading was at the coldest exreme (around -30 deg. F) then that's a good indication the ECT resistance was intermittently high (unless you live in Anchorage!) Check for an open in the ECT sensor ground and signal circuits and repair as necessary. If they appear okay, warm the engine up while monitoring the ECT for any intermittent jumps high or low. If there are replace the ECT.

b) If the saved info indicates that the engine coolant reading was at the warmest exreme (around 250+ deg.F) then that's a good indication the ECT resistance was intermittently low. Check for a short to ground on the signal circuit and repair as necessary. If it appears okay, warm the engine up while monitoring the ECT for any intermittent jumps high or low. If there are replace the ECT.

Other ECT sensor and circuit related DTCs: P0115, P0117, P0118, P0119, P0125, P0128
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P0128 Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)
This means that the engine's PCM detected that the engine has not reached the required temperature level within a specified amount of time after starting the engine. The intent of the P0128 code is to indicate a faulty thermostat. Similar codes: P0125

In determining the engine did not reach a "normal" temperature, it takes into account the length of time the vehicle has been running, the intake air temperature (IAT) sensor reading, the engine coolant temperature (ECT) sensor reading, and the speed of the vehicle.

Symptoms: You will likely not notice any drivability problems other than the MIL illumination.

Causes: A code P0128 may mean that one or more of the following has happened:
Low engine coolant level
Leaking or stuck open thermostat
Faulty cooling fan (running too much)
Faulty coolant temperature (ECT) sensor
Faulty intake air temperature (IAT) sensor

Possible Solutions: Past experience indicates that the most likely solution is to replace the thermostat. However here are some suggestions on troubleshooting and repairing a P0128 OBD-II code:
Verify coolant strength & level
Verify proper cooling fan operation (check if it's running more than it should). Replace if necessary.
Verify proper engine coolant temperature (ECT) sensor operation, replace if necessary.
Verify proper intake air temperature (IAT) sensor operation, replace if necessary.
If the above items check out good, replace the thermostat
If Nissan vehicle, check for Technical Service Bulletins (TSBs), as the ECM may need to be reprogrammed to correct the P0128 code



These codes are telling you that the engine temperature is not sufficient. This can be caused by a faulty coolant sensor,air in the cooling system,or a faulty computer.
The engine should run at 190 F & higher when warmed up. Scan the computer system to view engine temperature.

Keep us updated.

This means that the engine's PCM detected that the engine has not reached the required temperature level within a specified amount of time after starting the engine. The intent of the P0128 code is to indicate a faulty thermostat. Similar codes: P0125
In determining the engine did not reach a "normal" temperature, it takes into account the length of time the vehicle has been running, the intake air temperature (IAT) sensor reading, the engine coolant temperature (ECT) sensor reading, and the speed of the vehicle.
Symptoms You will likely not notice any drivability problems other than the MIL illumination.
Causes A code P0128 may mean that one or more of the following has happened:

• Low engine coolant level
• Leaking or stuck open thermostat
• Faulty cooling fan (running too much)
• Faulty coolant temperature (ECT) sensor
• Faulty intake air temperature (IAT) sensor

Possible Solutions Past experience indicates that the most likely solution is to replace the thermostat. However here are some suggestions on troubleshooting and repairing a P0128 OBD-II code:

• Verify coolant strength & level
• Verify proper cooling fan operation (check if it's running more than it should). Replace if necessary.
• Verify proper engine coolant temperature (ECT) sensor operation, replace if necessary.
• Verify proper intake air temperature (IAT) sensor operation, replace if necessary.
• If the above items check out good, replace the thermostat
• If Nissan vehicle, check for Technical Service Bulletins (TSBs), as the ECM may need to be reprogrammed to correct the P0128 code

Other ECT sensor and circuit related DTCs: P0115, P0116, P0117, P0118, P0119, P0125

is the temp gauge working? sounds like coolant temp sending unit... or a possible engine coolant temp sensor or ect sensor.

Heater fan or coolant fan ?

replace the sensor and or check the wiring socket going to the sensor

Fifteen minutes! you have bigger problems than only the fans the fans are controlled by a thermo switch that is heated by the coolant, If you have no coolant the sensor cannot activate But fifteen minutes seems like you may have a headgasket problem and steam cannot heat the coolant sensor.OperationNotesThe electric cooling fan operates when the engine cooling temperature exceeds a certain value. The cooling fan on this engine is controlled by the Powertrain Control Module (PCM) . The PCM turns the cooling fan ON by grounding the coil of the cooling fan relays when certain conditions are met. When the A/C is requested, the cooling fan will also be turned ON.

Power for the cooling fan motors are supplied through Maxifuses(R). The cooling fan relays are energized when current flows from the fuses in the Underhood Accessory Wiring Junction Block, and through the relay coils to ground through the PCM. The Coolant Fan 1 Relay Control Circuit is grounded for low speed fans operation. During low speed fans operation, both fans run at a slow speed. The Coolant Fan 1 Relay Control Circuit is grounded for high speed operation. During high speed fans operation, both fans run at high speed.

IMPORTANT: When certain Diagnostic Trouble Codes (DTCs) are present, the PCM may command the cooling fans to run all the time. Perform the A Powertrain On Board Diagnostic (OBD) System Check prior to diagnosing the engine cooling fans.

For more information regarding the Charging System, refer to Charging System Description , and Charging System Circuit Description in Starting and Charging.

If a problem that involves the low speed cooling fan relay control circuit exists, DTC P0480 Cooling Fan Relay 1 Control Circuit should set. If the problem affects the high speed cooling fan relay control circuit, DTC P0481 Cooling Fan Relay 2 Control Circuit should set. A problem with the ECT sensor should set DTC P0117 Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage, DTC P0118 Engine Coolant Temperature (ECT) Sensor Circuit High Voltage, DTC P1114 Engine Coolant Temperature (ECT) Sensor Circuit Intermittent Low Voltage, DTC P1115 Engine Coolant Temperature (ECT) Sensor Circuit Intermittent High Voltage. Any of these DTCs will affect cooling fan operation and should be diagnosed before using the Electric Cooling Fan Diagnosis.

For more information regarding the Cooling System refer to Engine Cooling Fan Description - Electric, and Cooling System Description in Cooling System.


Here is the electrical schematic and how it all is suppose to work,
If you need any further help please contact me Thank you,Randy If you find this information helpful please give me a good rating

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