Techniques for thawing a reductant injector and reductant tank prior to an injection attempt

1. A method, comprising:

determining, at a controller of an engine, the controller having one or more processors, whether an ambient temperature is less than a predetermined temperature indicative of frozen reductant in an exhaust system of the engine;

determining, at the controller, an injector thaw period for a reductant injector in the exhaust system when the ambient temperature is less than the predetermined temperature;

determining, at the controller, a tank thaw period for a reductant tank associated with the exhaust system, the reductant tank being configured to supply reductant to the reductant injector; and

controlling, by the controller, (i) a heater to heat the reductant tank for the tank thaw period and (ii) a current provided to the reductant injector for the injector thaw period, such that the tank thaw period and the injector thaw period end at a same time.

2. The method of claim 1 , wherein the injector thaw period is based on at least one of the ambient temperature, a speed of a vehicle powered by the engine, and a temperature within the reductant tank.

3. The method of claim 2 , wherein the injector thaw period is based on the ambient temperature and the vehicle speed.

4. The method of claim 3 , wherein the controller is configured to utilize a look-up table relating various ambient temperatures in an ambient temperature range to various injector thaw periods and various vehicle speeds to determine the injector thaw period.

5. The method of claim 4 , wherein the ambient temperature range is from approximately −40 degrees Celsius (° C.) to approximately 0° C., wherein the predetermined temperature is approximately 0° C., and wherein the various vehicle speeds include zero and non-zero.

6. The method of claim 1 , wherein supplying the current to the reductant injector includes commanding, by the controller, a maximum duty cycle of the reductant injector.

7. The method of claim 1 , further comprising:

calculating, at the controller, a difference between the tank thaw period and the injector thaw period to obtain a thaw delay; and

controlling, by the controller, the heater and supplying the current to the reductant injector based on the thaw delay.

8. The method of claim 1 , further comprising:

determining, at the controller, a resistance of a coil of the reductant injector; and

deactivating, by the controller, the reductant injector when the coil resistance reaches a predetermined critical resistance.

9. The method of claim 8 , further comprising:

reactivating, by the controller, the reductant injector when the coil resistance falls below a predetermined acceptable resistance that is less than the predetermined critical resistance.

10. The method of claim 9 , further comprising:

determining, at the controller, a temperature of the coil based on the coil resistance;

deactivating, by the controller, the reductant injector when the coil temperature reaches a predetermined critical temperature; and

reactivating, by the controller, the reductant injector when the coil temperature falls below a predetermined acceptable temperature that is less than the predetermined critical temperature.

11. An engine system comprising:

an engine configured to generate drive torque to propel a vehicle;

a selective catalytic reduction (SCR) system configured to treat exhaust gas produced by the engine, the SCR system comprising:

a solenoid-type reductant injector having a coil and configured to inject reductant into the exhaust gas,

an SCR catalyst configured to react with a mixture of the reductant and the exhaust gas and output treated exhaust gas,

a reductant tank configured to house the reductant,

a heater configured to heat the reductant tank, and

a reductant supply line configured to supply the reductant from the reductant tank to the reductant injector; and

a controller configured to, when an ambient temperature is less than a predetermined temperature indicative of frozen reductant, (i) enable the heater for a tank thaw period and (ii) provide current to the reductant injector for an injector thaw period, such that the tank thaw period and the injector thaw period end at a same time.

12. The engine system of claim 11 , wherein the controller is further configured to:

determine the injector thaw period for the reductant injector based on at least one of the ambient temperature, a speed of the vehicle, and a temperature within the reductant tank; and

determine the tank thaw period for the reductant tank.

13. The engine system of claim 12 , wherein the injector thaw period is based on the ambient temperature and the vehicle speed.

14. The engine system of claim 13 , wherein the controller is configured to utilize a look-up table relating various ambient temperatures in an ambient temperature range to various injector thaw periods and various vehicle speeds to determine the injector thaw period.

15. The engine system of claim 14 , wherein the ambient temperature range is from approximately −40 degrees Celsius (° C.) to approximately 0° C., wherein the predetermined temperature is approximately 0° C., and wherein the various vehicle speeds include zero and non-zero.

16. The engine system of claim 11 , wherein the current corresponds to a maximum duty cycle of the reductant injector.

17. The engine system of claim 11 , wherein the controller is further configured to:

calculate a difference between the tank thaw period and the injector thaw period to obtain a thaw delay; and

control the heater and supply the current to the reductant injector based on the thaw delay.

18. The engine system of claim 11 , wherein the controller is further configured to:

determine a resistance of the coil of the reductant injector;

deactivate the reductant injector when the coil resistance reaches a predetermined critical resistance; and

reactivate the reductant injector when the coil resistance falls below a predetermined acceptable resistance that is less than the predetermined critical resistance.

19. The engine system of claim 18 , wherein the controller is further configured to:

determine a temperature of the coil based on the coil resistance;

deactivate the reductant injector when the coil temperature reaches a predetermined critical temperature; and

reactivate the reductant injector when the coil temperature falls below a predetermined acceptable temperature that is less than the predetermined critical temperature.