slomo
Active VIP Member
This is absolutely false they have there own heater inside the tank which thaws the urea and it only injects urea during the regen to lower NOX and under lean cruise conditions that is all period
2012 D-Max
- Thread starter sledhead800
- Start date
slomo
Active VIP Member
Another false statement you could run the truck all day in -30 the urea could be frozen it does not make a difference as it does not inject urea until regen you may get a dtc from doing this too much as it will plug the dpf but if you give it a good drive down the highway after it should bring the soot mass down
slomo
Active VIP Member
Exhaust Aftertreatment System Description
System Overview
The diesel exhaust aftertreatment system is designed to reduce the levels of hydrocarbons (HC), carbon monoxide (CO), oxides of nitrogen (NOx), and particulate matter remaining in the vehicle’s exhaust gases. Reducing these pollutants to acceptable levels is achieved through a 3 stage process:
1. A diesel oxidation catalyst (DOC) stage
2. A selective catalyst reduction (SCR) stage
3. A diesel particulate filter (DPF) stage
In stage 1, the DOC removes exhaust HC and CO through an oxidation process. After the stage 1 treatment, diesel exhaust fluid (DEF), also known as reductant or urea, is injected into the exhaust gases prior to entering the SCR stage. Within the SCR, NOx is converted to nitrogen (N2), carbon dioxide (CO2) , and water vapor (H20) through a catalytic reduction fueled by the injected DEF. In the final or stage 3 process, particulate matter consisting of extremely small particles of carbon remaining after combustion are removed from the exhaust gas by the large surface area of the DPF.
Exhaust Aftertreatment System
1. NOx Sensor 1
2. EGT 1
3. Diesel Oxidation Catalyst (DOC)
4. EGT 2
5. Selective Catalyst Reduction (SCR)
6. EGT 3
7. NOx Sensor 2
8. Diesel Particulate Filter (DPF)
9. EGT 4
10. Exhaust Cooler
11. DPF Differential Pressure Sensor
12. Reductant Heater (3)
13. Reductant Pressure Sensor
14. Reductant Level/Temperature Sensor
15. Reductant Purge Valve
16. Reductant Pump
17. Reductant Injector
18. Hydrocarbon Injector (HCI)
Diesel Oxidation Catalyst (DOC) Operation
The DOC functions much like the catalytic converter used with gasoline fueled engines. As with all catalytic converters, the DOC must be hot in order to effectively convert the exhaust HC and CO into CO2 and H20. On cold starts, the exhaust gases are not hot enough to create temperatures within the DOC high enough to support full HC and CO conversion. The temperature at which full conversion occurs is known as light-off.
In addition to reducing emissions, the DOC also generates the exhaust heat needed by the SCR stage. Exhaust gas temperature (EGT) sensors are located upstream (EGT 1) and downstream (EGT 2) of the DOC. By monitoring the temperature differential between these two sensors, the ECM is able to confirm DOC light-off. Light-off is confirmed by a DOC output temperature that is greater than its input temperature.
In order to generate the high exhaust temperatures needed for regeneration, the aftertreatment system increases exhaust temperatures by injecting diesel fuel directly into the exhaust gases entering the DOC. This is accomplished by means of an ECM-controlled fuel injector, called the hydrocarbon injector (HCI), in the exhaust pipe upstream of the DOC. Injecting fuel directly into the exhaust rather than using a post-injection strategy greatly reduces oil/fuel dilution.
Proper DOC function requires the use of ultra-low sulfur diesel (ULSD) fuel containing less than 15 parts-per-million (ppm) sulfur. Levels above 15 ppm will reduce catalyst efficiency and eventually result in poor driveability and one or more DTCs being set.
Selective Catalyst Reduction (SCR) Operation
While diesel engines are more fuel efficient and produce less HC and CO than gasoline engines, as a rule they generate much higher levels of NOx. In order to meet today’s tighter NOx limits, an SCR catalyst, along with DEF, is used to convert NOx into N2, CO2, and H2O.
The ECM uses two smart NOx sensors to control exhaust NOx levels. The first NOx sensor is located in the turbocharger outlet and monitors the engine out NOx. The second NOx sensor is located in the exhaust pipe downstream of the SCR and monitors NOx levels exiting the aftertreatment system. The smart NOx sensors communicate with the ECM over the serial data line. Similar to the way the ECM uses oxygen sensor signals to maintain an optimum air/fuel ratio under various loads in gasoline applications, the ECM uses exhaust oxygen and NOx data from the NOx sensors to maintain the desired air/fuel ratio and to calculate the amount of DEF required to reduce exhaust NOx levels.
The NOx sensors incorporate an electric heater to quickly bring the sensors to operating temperature. As moisture remaining in the exhaust pipe could interfere with sensor operation, the ECM delays turning on the heaters until the exhaust temperature exceeds a calibrated value. This allows any moisture remaining in the exhaust pipe to boil off before it can effect NOx sensor operation. Depending on engine temperature at start up, the delay can be less than a minute or as long as two minutes. Typically, NOx sensor 1 will reach operating temperature faster than NOx sensor 2 as it’s closer to the engine’s hot exhaust. At idle or low engine speeds, NOx sensor 2 may require up to 5 minutes to reach operating temperature. The sensors must be hot before accurate exhaust NOx readings are available to the ECM.
DEF is a mixture of 66% deionized water and 34% urea. Within the SCR, exhaust heat converts the urea into ammonia (NH3) that reacts with NOx to form nitrogen, CO2, and water vapor. Optimum NOx reduction occurs at SCR temperatures above 250°C (480°F). At temperatures below 250°C, the incomplete conversion of urea forms sulfates that can poison the catalyst. To prevent this poisoning, the ECM suspends DEF injection when exhaust temperature falls below a calibrated limit.
The 6.6L (LML) engine uses exhaust gas temperature management to maintain the SCR catalyst within the optimum NOx conversion temperature range of 200–400°C (390–750°F). The ECM monitors EGT sensors located upstream (EGT 2) and downstream (EGT 3) of the SCR in order to determine if the SCR catalyst is within the temperature range where maximum NOx conversion occurs. The 6.6L (LGH) engine does not use exhaust gas temperature management; the ECM calculates SCR temperature based on the engine speed and load. For LGH applications, SCR temperatures are typically at the lower end of the temperature range under normal driving conditions; however, SCR temperatures will increase when hauling a trailer.
The smart NOx sensors provide a serial data message to the ECM with information on exhaust oxygen levels.
Diesel Exhaust Fluid (DEF) System
The DEF system consists of the following components located at the DEF reservoir:
• An electrically-operated reductant pump (12)
• A reductant purge valve (11)
• A reductant pressure sensor (9)
• A integrated reductant level sensor and reductant temperature sensor (10)
• Reductant system heaters (8)
The remaining DEF system component, an electrically-controlled reductant injector (13), is external to the reservoir.
The on-board reservoir holds approximately 19 liters (5 gallons) of DEF. An ECM controlled pump within the reservoir supplies pressurized DEF to the reductant injector located upstream of the SCR. A smart DEF level sensor within the reductant reservoir sends the ECM a serial data message indicating DEF level. The DEF pressure sensor provides the ECM with a voltage signal proportional to the reductant pressure generated by the DEF pump. The ECM varies the duty-cycle of the pump voltage to maintain reductant pressure within a calibrated range.
The state of the reductant purge valve determines whether DEF from the reductant pump is directed to the reductant injector or returned to the reservoir. In the normally de-energized state, the reductant purge valve directs reductant from the pump to the reductant injector. When the ignition is turned OFF, the ECM energizes both the reductant purge valve and reductant pump for about 30 to 45 seconds in order to purge the supply line of DEF. The ECM also commands the reductant injector to 100% to prevent vacuum from forming during the purge process. Purging prevents the reductant from freezing in the pump or supply line to the reductant injector.
The ECM energizes the reductant injector to dispense a precise amount of reductant upstream of the SCR in response to changes in exhaust NOx levels. Feedback from NOx sensors 1 and 2 allow the ECM to accurately control the amount of reductant supplied to the SCR. If more reductant is supplied to the SCR than is needed for a given NOx level, the excess reductant results in what is called ammonia slip where significant levels of ammonia exit the SCR. Since the NOx sensors are unable to differentiate between NOx and ammonia, ammonia slip will cause NOx sensor 2 to detect higher NOx levels than actually exist.
Cold Weather Operation
As reductant will freeze at temperatures below 0°C (32°F), there are 3 reductant heaters. Reductant heater 1 is in the reductant reservoir, reductant heater 2 is in the supply line to the reductant injector, and reductant heater 3 is at the reductant pump. The ECM monitors the reductant temperature sensor located within the reservoir in order to determine if reductant temperature is below its freeze point. If the ECM determines that the reductant may be frozen, it signals the Glow Plug Control Module (GPCM) to energize the reductant heaters.
Reductant pump operation is disabled for a calibrated amount of time to allow the heaters time to thaw the frozen reductant. Once the thaw period expires, the ECM energizes the reductant pump to circulate warm reductant through the de-energized reductant purge valve and back to the reservoir to speed thawing. The ECM looks for an increase in the reductant temperature to verify that the reductant reservoir heater is working.
System Overview
The diesel exhaust aftertreatment system is designed to reduce the levels of hydrocarbons (HC), carbon monoxide (CO), oxides of nitrogen (NOx), and particulate matter remaining in the vehicle’s exhaust gases. Reducing these pollutants to acceptable levels is achieved through a 3 stage process:
1. A diesel oxidation catalyst (DOC) stage
2. A selective catalyst reduction (SCR) stage
3. A diesel particulate filter (DPF) stage
In stage 1, the DOC removes exhaust HC and CO through an oxidation process. After the stage 1 treatment, diesel exhaust fluid (DEF), also known as reductant or urea, is injected into the exhaust gases prior to entering the SCR stage. Within the SCR, NOx is converted to nitrogen (N2), carbon dioxide (CO2) , and water vapor (H20) through a catalytic reduction fueled by the injected DEF. In the final or stage 3 process, particulate matter consisting of extremely small particles of carbon remaining after combustion are removed from the exhaust gas by the large surface area of the DPF.
Exhaust Aftertreatment System
1. NOx Sensor 1
2. EGT 1
3. Diesel Oxidation Catalyst (DOC)
4. EGT 2
5. Selective Catalyst Reduction (SCR)
6. EGT 3
7. NOx Sensor 2
8. Diesel Particulate Filter (DPF)
9. EGT 4
10. Exhaust Cooler
11. DPF Differential Pressure Sensor
12. Reductant Heater (3)
13. Reductant Pressure Sensor
14. Reductant Level/Temperature Sensor
15. Reductant Purge Valve
16. Reductant Pump
17. Reductant Injector
18. Hydrocarbon Injector (HCI)
Diesel Oxidation Catalyst (DOC) Operation
The DOC functions much like the catalytic converter used with gasoline fueled engines. As with all catalytic converters, the DOC must be hot in order to effectively convert the exhaust HC and CO into CO2 and H20. On cold starts, the exhaust gases are not hot enough to create temperatures within the DOC high enough to support full HC and CO conversion. The temperature at which full conversion occurs is known as light-off.
In addition to reducing emissions, the DOC also generates the exhaust heat needed by the SCR stage. Exhaust gas temperature (EGT) sensors are located upstream (EGT 1) and downstream (EGT 2) of the DOC. By monitoring the temperature differential between these two sensors, the ECM is able to confirm DOC light-off. Light-off is confirmed by a DOC output temperature that is greater than its input temperature.
In order to generate the high exhaust temperatures needed for regeneration, the aftertreatment system increases exhaust temperatures by injecting diesel fuel directly into the exhaust gases entering the DOC. This is accomplished by means of an ECM-controlled fuel injector, called the hydrocarbon injector (HCI), in the exhaust pipe upstream of the DOC. Injecting fuel directly into the exhaust rather than using a post-injection strategy greatly reduces oil/fuel dilution.
Proper DOC function requires the use of ultra-low sulfur diesel (ULSD) fuel containing less than 15 parts-per-million (ppm) sulfur. Levels above 15 ppm will reduce catalyst efficiency and eventually result in poor driveability and one or more DTCs being set.
Selective Catalyst Reduction (SCR) Operation
While diesel engines are more fuel efficient and produce less HC and CO than gasoline engines, as a rule they generate much higher levels of NOx. In order to meet today’s tighter NOx limits, an SCR catalyst, along with DEF, is used to convert NOx into N2, CO2, and H2O.
The ECM uses two smart NOx sensors to control exhaust NOx levels. The first NOx sensor is located in the turbocharger outlet and monitors the engine out NOx. The second NOx sensor is located in the exhaust pipe downstream of the SCR and monitors NOx levels exiting the aftertreatment system. The smart NOx sensors communicate with the ECM over the serial data line. Similar to the way the ECM uses oxygen sensor signals to maintain an optimum air/fuel ratio under various loads in gasoline applications, the ECM uses exhaust oxygen and NOx data from the NOx sensors to maintain the desired air/fuel ratio and to calculate the amount of DEF required to reduce exhaust NOx levels.
The NOx sensors incorporate an electric heater to quickly bring the sensors to operating temperature. As moisture remaining in the exhaust pipe could interfere with sensor operation, the ECM delays turning on the heaters until the exhaust temperature exceeds a calibrated value. This allows any moisture remaining in the exhaust pipe to boil off before it can effect NOx sensor operation. Depending on engine temperature at start up, the delay can be less than a minute or as long as two minutes. Typically, NOx sensor 1 will reach operating temperature faster than NOx sensor 2 as it’s closer to the engine’s hot exhaust. At idle or low engine speeds, NOx sensor 2 may require up to 5 minutes to reach operating temperature. The sensors must be hot before accurate exhaust NOx readings are available to the ECM.
DEF is a mixture of 66% deionized water and 34% urea. Within the SCR, exhaust heat converts the urea into ammonia (NH3) that reacts with NOx to form nitrogen, CO2, and water vapor. Optimum NOx reduction occurs at SCR temperatures above 250°C (480°F). At temperatures below 250°C, the incomplete conversion of urea forms sulfates that can poison the catalyst. To prevent this poisoning, the ECM suspends DEF injection when exhaust temperature falls below a calibrated limit.
The 6.6L (LML) engine uses exhaust gas temperature management to maintain the SCR catalyst within the optimum NOx conversion temperature range of 200–400°C (390–750°F). The ECM monitors EGT sensors located upstream (EGT 2) and downstream (EGT 3) of the SCR in order to determine if the SCR catalyst is within the temperature range where maximum NOx conversion occurs. The 6.6L (LGH) engine does not use exhaust gas temperature management; the ECM calculates SCR temperature based on the engine speed and load. For LGH applications, SCR temperatures are typically at the lower end of the temperature range under normal driving conditions; however, SCR temperatures will increase when hauling a trailer.
The smart NOx sensors provide a serial data message to the ECM with information on exhaust oxygen levels.
Diesel Exhaust Fluid (DEF) System
The DEF system consists of the following components located at the DEF reservoir:
• An electrically-operated reductant pump (12)
• A reductant purge valve (11)
• A reductant pressure sensor (9)
• A integrated reductant level sensor and reductant temperature sensor (10)
• Reductant system heaters (8)
The remaining DEF system component, an electrically-controlled reductant injector (13), is external to the reservoir.
The on-board reservoir holds approximately 19 liters (5 gallons) of DEF. An ECM controlled pump within the reservoir supplies pressurized DEF to the reductant injector located upstream of the SCR. A smart DEF level sensor within the reductant reservoir sends the ECM a serial data message indicating DEF level. The DEF pressure sensor provides the ECM with a voltage signal proportional to the reductant pressure generated by the DEF pump. The ECM varies the duty-cycle of the pump voltage to maintain reductant pressure within a calibrated range.
The state of the reductant purge valve determines whether DEF from the reductant pump is directed to the reductant injector or returned to the reservoir. In the normally de-energized state, the reductant purge valve directs reductant from the pump to the reductant injector. When the ignition is turned OFF, the ECM energizes both the reductant purge valve and reductant pump for about 30 to 45 seconds in order to purge the supply line of DEF. The ECM also commands the reductant injector to 100% to prevent vacuum from forming during the purge process. Purging prevents the reductant from freezing in the pump or supply line to the reductant injector.
The ECM energizes the reductant injector to dispense a precise amount of reductant upstream of the SCR in response to changes in exhaust NOx levels. Feedback from NOx sensors 1 and 2 allow the ECM to accurately control the amount of reductant supplied to the SCR. If more reductant is supplied to the SCR than is needed for a given NOx level, the excess reductant results in what is called ammonia slip where significant levels of ammonia exit the SCR. Since the NOx sensors are unable to differentiate between NOx and ammonia, ammonia slip will cause NOx sensor 2 to detect higher NOx levels than actually exist.
Cold Weather Operation
As reductant will freeze at temperatures below 0°C (32°F), there are 3 reductant heaters. Reductant heater 1 is in the reductant reservoir, reductant heater 2 is in the supply line to the reductant injector, and reductant heater 3 is at the reductant pump. The ECM monitors the reductant temperature sensor located within the reservoir in order to determine if reductant temperature is below its freeze point. If the ECM determines that the reductant may be frozen, it signals the Glow Plug Control Module (GPCM) to energize the reductant heaters.
Reductant pump operation is disabled for a calibrated amount of time to allow the heaters time to thaw the frozen reductant. Once the thaw period expires, the ECM energizes the reductant pump to circulate warm reductant through the de-energized reductant purge valve and back to the reservoir to speed thawing. The ECM looks for an increase in the reductant temperature to verify that the reductant reservoir heater is working.
slomo
Active VIP Member
Straight out of my manual I hope this clears up any misconceptions
pfi572
Active VIP Member
Thanks slomo for the clarification as i have a 2012 also and has worked great so far through the cold. Hope it keeps working. 37000 kms and don't want to pull it all off if possible.
Like it for working out of hotels as no stink for others parked near it or for people in hotel.
Like it for working out of hotels as no stink for others parked near it or for people in hotel.
i was reading on a diesel forum and they were saying that the new diesel motors only needed to be warmed up for a minute or two before driving, even the big class 9 trucks... anything more is a comfort thing. i still like 5 mins. its a losing cycle if you keep idling your truck at low idle, idle time increases the soot in the dpf so the more regens required to clean the dpf which leads to increased fuel usage... if you want to idle your lml run out to your truck start it up lock the parking brake and push up a bunch of times on the cruise control... keeps the truck at high idle so it does a better job of keeping everything warm
that is if your truck has the high idle switch
that is if your truck has the high idle switch
growly
Active VIP Member
Don't know about the GM DEF systems, but the Dodge one uses engine coolant to thaw the fluid.
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