Both fans on all the time

[odd boy]

Hi,

I have camaro 98, I swapped both heads then both fans r on all the time. I know that there is no relation between the swap and the fan but it seems like the mechanics did a grounding problem. Any help??

I made some trials, like shutting them off by the DVT and it worked. And the samething happened with the AC.

[joecar]

Check that the ECT sensor is connected and reading correctly.

[odd boy]

I did, it is working and ECT is below on set point

[ChipsByAl]

If DVT control can turn the fans off, then the PCM is in control. Make sure you don't have any codes setting, this could make the fans come on. Post up the tun file, something may show up.
Al

[odd boy]

here it is

5145

[roy]

Are all the grounds on the back of the heads ? Any pending codes?

[odd boy]

IAT code and compressor clutch

[joecar]

Do this:
- remove the fan relays and see if the fans stop;
- if the fans stop, then faulty relay(s) or short circuit upstream of relays (causing relays to pull on).
- if fans continue, then short circuit downstream of relays.

[odd boy]

I did that before, when I remove them, fans stop!! I will check the circut

[roy]

Are both fans coming on the moment the car starts up or after a few minutes or after the A/C is engaged. Did you have any A/C work done or r/r a component. I am looking at the schematic and it is pretty straight forward. I am just wondering if it is an input that the PCM is reading incorrect.
The ones that I canthink of is:
ECT- exceeds 113'c fans come on
A/C pressure enable - pressure is greater than 275 psi fans come on

Also if you have fbody service shop manual, look on page 6-1123 for electrical cooling fan disc. It gives more info than Ican type.

[odd boy]

Are both fans coming on the moment the car starts up or after a few minutes or after the A/C is engaged. Did you have any A/C work done or r/r a component. I am looking at the schematic and it is pretty straight forward. I am just wondering if it is an input that the PCM is reading incorrect.
The ones that I canthink of is:
ECT- exceeds 113'c fans come on
A/C pressure enable - pressure is greater than 275 psi fans come on

Also if you have fbody service shop manual, look on page 6-1123 for electrical cooling fan disc. It gives more info than Ican type.

Yes both are on, on the moment the cars starts up, regardless what the AC condition is.

I have never done anything to the AC, just fill it whenever needed.

[roy]

IAT code and compressor clutch
pardon my asking, but what is the DTC number

[odd boy]

here it is

[roy]

The two DTCs that Iknow of that causes the fan to come on



A failure in the Engine Coolant Temperature Sensor or circuit will set one of the following
DTCs:
DTC P0117 Engine Coolant Temperature Sensor Circuit Low Voltage
Conditions for running DTC P0117
• The engine run time is greater than 10 seconds
Conditions for setting DTC P0117
• The engine coolant temperature is greater than 139°C
• All conditions met for at least 45 seconds
Action taken when DTC P0117 Sets
• The PCM illuminates the Check Powertrain Lamp when the diagnostic runs and fails
• The PCM will substitute a coolant temperature default value
The PCM arrives at this default value, by using current intake air temperature, then counting upward to
116°C at a rate of approximately 7 degrees per minute
• PCM will turn on the electric engine cooling fans This is a FAIL-SAFE action by the PCM to prevent a
possible engine overheat condition, since the DTC indicates an unknown actual coolant temperature
• The PCM records the operating conditions at the time the diagnostic fails The PCM stores this information
in the Freeze Frame/Failure Records
Conditions for clearing the Check Powertrain Lamp and DTC P0117
• The PCM turns the Check Powertrain Lamp OFF when the diagnostic runs and does not fail
• A last test failed (current DTC) clears when the diagnostic runs and does not fail
DTC P0118 Engine Coolant Temperature Sensor Circuit High Voltage
Conditions for running DTC P0118
• The engine run time is greater than 10 seconds
Conditions for setting DTC P0118
• The engine coolant temperature is at or below -38 9°C
• All conditions met for at least 45 seconds
Action taken when DTC P0118 Sets
• The PCM illuminates the Check Powertrain Lamp when diagnostic runs and fails
• The PCM will substitute a coolant temperature default value
The PCM arrives at this default value, by using current intake air temperature, then counting upward to
116°C at a rate of approximately 7 degrees per minute
• PCM will turn on the electric engine cooling fans This is a FAIL-SAFE action by the PCM to prevent a
possible engine overheat condition, since the DTC indicates an unknown actual coolant temperature
• The PCM records the operating conditions at the time the diagnostic fails The PCM stores this information
in the Freeze Frame/Failure Records
Conditions for clearing the Check Powertrain Lamp and DTC P0118
• The PCM turns the Check Powertrain Lamp OFF when the diagnostic runs and does not fail
• A last test failed (current DTC) clears when the diagnostic runs and does not fail
GEN


These are the conditions to turn on the fans.



The PCM will disengage the A/C compressor at low or
high refrigerant pressures and control the operation of
the engine cooling fans.





ENGINE COOLING FAN LOW SPEED
The engine cooling fan low speed relay is energised by the BCM.
The cooling fan low speed relay will be turned ON when:
• The A/C request indicated (YES) and either:
• the vehicle speed is less than 30 km/h.
or
• A/C pressure is greater than 1500 kPa
or
• The coolant temperature is greater than 98°C.
• or
• If the coolant temperature is greater than 113°C, when the ignition is switched off, the relay is energised for
approximately four minutes, this is known as Low Fan Run On.
• or
• If an engine coolant temperature sensor fault is detected and a DTC such as DTC P0177, P0188, P01114
or P01115 is set.
The cooling fan low speed relay will be turned OFF when any of the following conditions have been met:
• An A/C request is not indicated (NO) and the coolant temperature is less than 95°C.
• or
• An A/C request is indicated (YES) and the vehicle speed is greater than 50 km/h and A/C pressure is less
than 1170 kPa and the coolant temperature is less than 98°C.

[roy]

PartII



ENGINE COOLING FAN HIGH SPEED
• The engine cooling fan high speed relay is controlled by the PCM. The PCM will only turn ON' the engine
cooling fan high speed relay fan if the engine cooling fan low speed relay has been "ON" for two seconds
and the following conditions are satisfied.
• There is a BCM message response fault which will cause a PIM DTC B2002.
• An engine coolant temperature sensor fault is detected and a DTC such as DTC P0177, P0188, P01114 or
P01115 is set.
• Coolant temperature greater than 108°C.
• The A/C refrigerant pressure is greater than 2400 kPa.
If the low speed fan was OFF when the criteria was met to turn the high speed fan ON, the high speed fan will
come ON 5 seconds after the low speed fan is turned ON. If both the engine cooling fan relays are ON, the
PCM will turn OFF the high speed relay when:
• The engine coolant temperature is less than 102°C.
• A/C request not indicated (NO).
• A/C request indicated (YES) and A/C pressure is less than 1900 kPa.
Note: All cooling fans will be turned off in the vehicle speed is greater than 104 kph.


Hope this helps.

[odd boy]

many, thanks. I just replaced the ECU it is very fine now. It looks like the ECU is not good