Low coolant temperature fault diagnostic systems and methods

1. A diagnostic system for a vehicle, comprising:

a comparison module that indicates whether a temperature of engine coolant is less than a first predetermined temperature;

a temperature determination module that determines the first predetermined temperature based on at least one of a flowrate of the engine coolant and an opening of a thermostat;

a disabling module that disables the comparison module until the temperature of the engine coolant is greater than a second predetermined temperature;

a fault indication module that diagnoses a fault in response to the comparison module indicating that the temperature of the engine coolant is less than the first predetermined temperature; and

a remedial action module that illuminates a malfunction indicator lamp (MIL) in response to the fault indication module diagnosing the fault.

2. The diagnostic system of claim 1 wherein the disabling module disables the comparison module, after the temperature of the engine coolant is greater than the second predetermined temperature, when a fuel cutoff (FCO) event occurs.

3. The diagnostic system of claim 2 wherein the disabling module disables the comparison module for a predetermined period after the FCO event ends.

4. The diagnostic system of claim 1 wherein the disabling module disables the comparison module, after the temperature of the engine coolant is greater than the second predetermined temperature, when a deceleration fuel cutoff (DFCO) event occurs.

5. The diagnostic system of claim 1 wherein the disabling module disables the comparison module, after the temperature of the engine coolant is greater than the second predetermined temperature, when a power produced by an engine is less than a predetermined power.

6. The diagnostic system of claim 5 wherein the disabling module disables the comparison module for a predetermined period after the power produced by the engine becomes greater than the predetermined power.

7. The diagnostic system of claim 1 wherein, after the temperature of the engine coolant is greater than the second predetermined temperature, the disabling module disables the comparison module:

when a fuel cutoff (FCO) event occurs;

for a first predetermined period after the FCO event ends;

when a power produced by an engine is less than a predetermined power; and

for a second predetermined period after the power produced by the engine becomes greater than the predetermined power.

8. The diagnostic system of claim 1 wherein the first predetermined temperature is greater than the second predetermined temperature.

9. The diagnostic system of claim 1 further comprising a remedial action module that selectively adjusts at least one engine operating parameter to increase the temperature of the engine coolant in response to the fault indication module diagnosing the fault.

10. A diagnostic method for a vehicle, comprising:

indicating whether a temperature of engine coolant is less than a first predetermined temperature;

determining the first predetermined temperature based on at least one of a flowrate of the engine coolant and an opening of a thermostat;

disabling the indication of whether the temperature of the engine coolant is less than the first predetermined temperature until the temperature of the engine coolant is greater than a second predetermined temperature;

diagnosing a fault in response to the indication that the temperature of the engine coolant is less than the first predetermined temperature; and

illuminating a malfunction indicator lamp (MIL) in response to the diagnosis of the fault.

11. The diagnostic method of claim 10 further comprising disabling the indication of whether the temperature of the engine coolant is less than the first predetermined temperature, after the temperature of the engine coolant is greater than the second predetermined temperature, when a fuel cutoff (FCO) event occurs.

12. The diagnostic method of claim 11 further comprising disabling the indication of whether the temperature of the engine coolant is less than the first predetermined temperature for a predetermined period after the FCO event ends.

13. The diagnostic method of claim 10 further comprising disabling the indication of whether the temperature of the engine coolant is less than the first predetermined temperature, after the temperature of the engine coolant is greater than the second predetermined temperature, when a deceleration fuel cutoff (DECO) event occurs.

14. The diagnostic method of claim 10 further comprising disabling the indication of whether the temperature of the engine coolant is less than the first predetermined temperature, after the temperature of the engine coolant is greater than the second predetermined temperature, when a power produced by an engine is less than a predetermined power.

15. The diagnostic method of claim 14 further comprising disabling the indication of whether the temperature of the engine coolant is less than the first predetermined temperature for a predetermined period after the power produced by the engine becomes greater than the predetermined power.

16. The diagnostic method of claim 10 further comprising, after the temperature of the engine coolant is greater than the second predetermined temperature, disabling the indication of whether the temperature of the engine coolant is less than the first predetermined temperature:

when a fuel cutoff (FCO) event occurs;

for a first predetermined period after the FCO event ends;

when a power produced by an engine is less than a predetermined power; and

for a second predetermined period after the power produced by the engine becomes greater than the predetermined power.

17. The diagnostic method of claim 10 wherein the first predetermined temperature is greater than the second predetermined temperature.

18. The diagnostic method of claim 10 further comprising selectively adjusting at least one engine operating parameter to increase the temperature of the engine coolant in response to the diagnosis of the fault.