794 AC Off-Highway Truck Caterpillar


Selective Catalytic Reduction Warning System

Usage:

794 AC HRT
The selective catalytic reduction (SCR) system is a system used to reduce NOx emissions from the engine. Diesel exhaust fluid (DEF) is pumped from the DEF tank and is sprayed into the exhaust stream. The DEF reacts with the SCR catalyst to reduce NOx.

The engine and emissions control system shall be operated, used, and maintained in accordance with the instructions provided to the end user to maintain the emissions performance of the engine within the requirements applicable to the category of the engine. No deliberate tampering with, or misuse of the engine emissions control system should take place. In particular regarding deactivating, or not maintaining the SCR system.


NOTICE

Stopping the engine immediately after the engine has been working under load can result in overheating of SCR components.

Refer to the Operation and Maintenance Manual, "Stopping the Engine" procedure to allow the engine to cool and to prevent excessive temperatures in the turbocharger housing and the DEF injector.



NOTICE

Allow at least 2 minutes after shutting down the engine before you turn the battery disconnect switch to OFF. Disconnecting the battery power too soon will prevent purging of the DEF lines after the engine is shut down.


Definitions

Observe the following definitions.

Notification - Action taken by the system to alert the operator of pending Inducement.

Inducement - Engine derates, vehicle speed limits, or other actions intended to prompt the operator to repair or maintain the emission control system.

Inducement Trigger - Fault conditions that result in activation of the inducement strategy. DEF level inducement faults have a diagnostic fault code. DEF quality fault, SCR tampering fault, and SCR system fault will all have a related diagnostic fault code along with an inducement diagnostic fault code.

First occurrence - A SCR system fault becomes active for the first time.

Repeat occurrence - SCR system fault becomes active again within 40 hours of the first occurrence.

Safe Harbor Mode (Worldwide) - Safe harbor mode is a 20 minute engine run time period. During the Safe Harbor Mode the engine can be operated with full power after reaching a level 3 inducement. Once in level 3 inducement, the operator can perform a key cycle and the engine will enter safe Harbor Mode. Safe Harbor Mode can only be implemented once. Safe harbor mode is not allowed for DEF level inducements with Worldwide configuration

Safe Harbor Mode (European Union) - Safe Harbor Mode is a 30 minute engine run time period. During the Safe Harbor Mode the engine can be operated with full power after reaching a level 3 inducement. Once in level 3 inducement, the operator can perform a key cycle and the engine will enter Safe Harbor Mode. Safe Harbor Mode can only be implemented up to three times.


NOTICE

It is essential to take prompt action to rectify any incorrect operation, use, or maintenance of the emissions SCR control system in accordance with the rectification measures indicated by the warnings listed on the following pages.


Carbon Dioxide (CO2) Emissions Statement

Emissions regulations require that the value of the CO2 emissions be reported to the end user. For this engine, 677 g/kWh was determined to be the CO2 value during the EU type approval process. This value was recorded in EU type approval certificate. This CO2 measurement results from testing over a fixed test cycle, under laboratory conditions, with a parent engine representative of the engine family. This value shall not imply or express any guarantee of the performance of a particular engine.

Selective Catalytic Reduction Performance and Hydrocarbons

Diesel engine combustion produces hydrocarbons (HC) in the exhaust gas emissions. Engine HC emissions are part of normal engine operation, and the levels are further reduced with the use of the SCR aftertreatment system. When the engine is idling or exhaust temperatures are low for extended periods of time, hydrocarbons (HC) in the exhaust gas stream will collect on the Selective Catalyst Reduction (SCR) catalyst. When sufficient HC has collected on the SCR catalyst, and the exhaust temperatures increase too quickly due to rapid load increase, the SCR catalyst can be permanently damaged.

To protect the SCR system, the ECM monitors the HC level on the SCR catalyst. During the extended idling period (particularly in cold climate), action will be taken by the ECM to increase the engine exhaust temperatures safely to reduce the amount of hydrocarbon. In order for this strategy to work, the equipment must be stationary with the parking brake engaged (if equipped) as well other enabling conditions have to be met. Once a pre-determined level of HC loading is reached, the machine uses an automatic loading feature to generate the needed exhaust temperature. This temperature is accomplished through either a Torque Converter stall (mining truck) or hydraulic stall (wheel loader), and does not require an operator to be present. This action may include elevated engine speed, cylinder cutout, torque converter and/or hydraulic pump operation. The action is taken automatically by the machine control system when certain conditions are met. Increased engine speed and noise generation are normal. A message is shown on a Cab display to indicate that Engine speed is elevated.

If the engine ECM cannot get the hydrocarbon levels below an acceptable threshold after a certain amount of time, there will be an alert informing the operator that action must be taken. If action is taken, the alert will clear.

If the operator is not present, or cannot act, and the exhaust temperatures do not increase after a certain time, the engine will shut down. The engine may be restarted, but if the engine ECM determines that the exhaust temperatures have not risen high enough or the hydrocarbon levels on the SCR catalyst have not started to drop, the engine will be shut down again.

To get the hydrocarbon buildup off the SCR catalyst once the alert or the shutdown has occurred, the operator must either put the equipment to work as soon as possible to elevate the exhaust temperatures in normal operating range to continue to reduce the amount of hydrocarbon on the SCR Catalyst, or the “Aftertreatment System Functional Test” must be performed using Cat ET.

Depending on ambient conditions, repeated Aftertreatment System Functional Tests may be required to get hydrocarbon levels on the SCR catalyst down to an acceptable level. When the low exhaust temperature code goes to “Logged”, the operator must put the machine to work to continue to reduce the hydrocarbon levels on the SCR catalyst. Failure to reduce the hydrocarbon levels may result in more shutdowns.

Note: To prevent damage to the SCR catalysts, the engine ECM may continue to derate the engine during normal operation for a short time after the codes have cleared.

Inducement Strategy for DEF Level



Illustration 1g06272376
DEF Level Normal


Illustration 2g06146152

If the DEF level falls below 18%, an amber indicator will illuminate next to the DEF level gauge on the dash. To avoid further inducements, turn the key to the OFF position and add DEF to the DEF tank.



Illustration 3g06146157

If the DEF level falls below 12.5%, a level 1 inducement event will occur. The check engine lamp and the emissions malfunction indicator lamp will illuminate. The amber indicator next to the DEF level gauge on the dash will remain lit.



Illustration 4g06146163

If the DEF level is below 7.5%, a level 2 inducement event will occur. The check engine lamp and the emissions malfunction indicator lamp will illuminate and a flashing action indicator will also illuminate. The amber indicator next to the DEF level gauge on the dash will remain lit. If the ECM is configured to "Reduced Performance" and the DEF level has reached 1%, the machine will be limited to 75% torque.



Illustration 5g06146172

If the ECM is configured to "Reduced Performance" and the DEF tank has been emptied of all DEF, the engine will be in a level 3 final inducement. If the ECM is configured to "Reduced Time" and the DEF level is 3%, the engine will be in a level 3 final inducement. Prior to final inducement the check engine lamp and the emissions malfunction indicator lamp will illuminate, the flashing action indicator will illuminate, and an audible alarm will sound 20 seconds prior to the final inducement. The engine will be taken to low idle or will be shut down. Once shut down, the engine can be restarted for 5 minute periods at reduced speed and torque. If set to idle, the engine will idle indefinitely at reduced torque. The amber indicator next to the DEF level gauge on the dash will remain lit.

Note: Turn the key to the OFF position and add DEF to the DEF tank to reset the DEF level inducement.

Inducement Strategy for DEF Quality, Tampering, and SCR System Fault



Illustration 6g03623190

The emissions malfunction indicator lamp will illuminate for a fault resulting from poor DEF quality, SCR system tampering, or an SCR system fault. If the fault is the result of poor DEF quality, SCR system tampering, or SCR system fault, a first occurrence will result in a level 1 inducement. Repeat occurrences will result in additional level 1 inducements.



Illustration 7g03623191

If a fault condition exists for the entire duration of inducement level 1, the strategy advances to inducement level 2. The check engine lamp and the emissions malfunction indicator lamp will illuminate and a flashing action indicator will also illuminate for a fault resulting from poor DEF quality, SCR system tampering, or an SCR system fault.



Illustration 8g03623193

If a fault condition exists for the entire duration of inducement level 2, the strategy advances to inducement level 3. The check engine lamp and the emissions malfunction indicator lamp will illuminate, flashing action indicator will illuminate, and an audible alarm will sound 20 seconds prior to the level 3 inducement. The engine will be taken to low idle or will be shut down. After the level 3 inducement you may cycle the key one time only, which will allow 20 minutes for Worldwide and EPA Engine Emission Operator Inducement Regulation Configuration and 30 minutes for EU Engine Emission Operator Inducement Regulation Configuration, of engine run time with full torque. After 20 or 30 minutes, the engine will be in level 3 final inducement and will allow idle only or be shut down until the issue has been resolved. Once shut down, the engine can be restarted for 5 minute periods at reduced speed and torque. If set to idle, the engine will idle indefinitely at reduced torque.

Note: Contact your Cat dealer for repairs if a fault occurs.

Inducement Emergency Override for Cat Engines Equipped with Selective Catalytic Reduction Systems (If Equipped)

Note: The inducement emergency override will only be allowed on a select number of machines that may be used in emergency situations. Contact your Cat dealer to find out if your machine is allowed to have this feature.

Inducement emergency override can only be enabled using Caterpillar supplied passwords. The feature is disabled by default. The feature will be enabled at the factory if allowed. If the customer wants the feature enabled after delivery of engine, the customer will need to contact the Cat dealer. Inducement emergency override is regulated by the Environmental Protection Agency (EPA) and only allowed in the United States. Operator Inducement emergency override is not supported in Europe, and is not allowed to be used in Japan. For detailed information on activating, deactivating, or resetting override, contact your Cat dealer. Before you attempt the procedures documented in this manual, make sure that you have read and understand the information in this document.

The United States EPA requires the limiting of engine speed and/or power (derate) in certain conditions, to help ensure proper functioning of the engines emission control system. The EPA allows the temporary disabling of these limits (restoration of full engine speed and power capability) during a qualified emergency situation. The EPA defines a qualified emergency situation as a significant direct or indirect risk to human life. Below are examples of direct versus indirect risks.

Direct - An emission control condition that inhibits performance of an engine being used to rescue a person from life-threatening situation.

Indirect - An emission control condition that inhibits performance of an engine being used to provide electrical power to a data center that routes 911 emergency response communications.

The emissions-related derate can be disabled for up to 120 hours of engine operation. The temporary disabling of emissions-related derate is referred to as "Inducement Emergency Override" and must be reported to the United States EPA. The override can only be enabled or disabled by an authorized Cat dealer using Caterpillar supplied passwords. Once enabled, the override can be activated through the electronic display menu in the cab (if equipped). Upon activation, the check engine and action lamps will be illuminated until and the override is reset. A code indicating that the inducement emergency override is active will also be active until the override is reset. The override can only be reset by the engine manufacturer, Caterpillar. A Cat dealer can reset the override using Caterpillar supplied passwords. Improper use of the override, failure to deactivate the override when the emergency has ended, and failure to report use of the override is prohibited under federal regulations and subject to penalties imposed by the United States EPA. The civil penalty per day operated in violation can be severe.


NOTICE

When the inducement emergency override is active, damage to aftertreatment and engine components can occur. Never use the override longer than necessary and always fix the root cause of the inducement as soon as possible. There will always be a diagnostic code indicating root cause of the inducement. Refer to the troubleshooting guide for how to fix inducement related failures.


Override Activation Method

There are two options for setting the override, using Cat Electronic Technician (ET) or through the electronic display menu in the cab (if equipped). If the override has already been enabled by an authorized Cat dealer, then the operator can turn on the override without further input from Caterpillar. Upon activation, the check engine and action lamps will illuminate to alert the operator that the override is active. The override must be paused by the operator if the emergency ends before the 120 hours of override operation has expired. While paused, the equipment will be subject to derates. Once paused, the override can be activated again if the 120-hour time period has not expired and if an emergency situation still exists. Per federal regulations, the operator must fill out the Override Usage Report below and provide the report to Caterpillar within 60 days of activating the override.

Setting the Override through Cat Electronic Technician (ET)

  • Go to "Configuration Parameters"

  • Select "Aftertreatment Configuration"

  • Select "Operator Inducement Emergency Override Activation" to activate the override

  • The "Value" field should be switched to "Activated" (to pause the override change the "Value" field to "Not Activated")

Setting the Override through Electronic Display Menu

Machine applications will be able to activate or deactivate the override through the electronic display menu in the cab. The override will only be available when engine is already in inducement (derated). Operators must be trained properly to understand where override is located and that there could be severe penalties as mentioned above for misusing the override. There will be a warning on display stating: "EMERGENCY USE ONLY. SEE OWNERS MANUAL. PENALTIES APPLY FOR MISUSE".

Resetting the Override

The override needs to be reset through Cat Electronic Technician (ET) whenever the override has expired. The override cannot be used again until the override is reset. The override should also be reset whenever the emergency has ended, regardless if the override has expired or not (i.e. accumulated 120 hours). The check engine and action lamps will continue to be illuminated until the override is reset. The code indicating that the inducement emergency override is active will also continue to be active until the override is reset. The override may be reset at any point after the initial activation. The override can only be reset by the engine manufacturer, Caterpillar, or an authorized Cat dealer using Caterpillar supplied passwords.

Override Usage Report

To comply with federal regulations, the operator must report usage of the override to Caterpillar Inc. within 60 days of activating the override. Failure to meet this reporting requirement may subject the operator to penalties under 40 CFR 1068.101. Caterpillar Inc.will in turn report override usage annually to the United States EPA. Although submitted to Caterpillar Inc., the override usage reports are deemed to be submissions to the United States EPA. Federal regulations prohibit submitting false information. The following information must be included in the report:

  • Contact name, mail and e-mail addresses, and telephone number for the responsible company or entity

  • A description of the emergency situation, the location of the engine during the emergency, and the contact information for an official who can verify the emergency situation (such as a county sheriff, fire marshal, or hospital administrator)

  • The reason for the activation of the override during the emergency situation, such as the lack of DEF, or the failure of an emission-related sensor when the engine was needed to respond to an emergency situation

  • The engine serial number (or equivalent)

  • A description of the extent and duration of the engine operation while the override was active, including a statement describing whether the override was manually deactivated (paused) after the emergency situation ended

The Override Usage Report may be sent via e-mail or regular mail to one of the following addresses:

Email :

Emissions_Compliance@cat.com

Regular Mail :

Caterpillar Inc.
P.O. Box 600
Mossville, IL 61552-0600
Attention: Emissions Compliance Manager

Caterpillar Information System:

794 AC Off-Highway Truck Battery Disconnect Switch
794 AC Off-Highway Truck Monitoring System
336 Excavator Machine Systems Main Hydraulic Pump - Remove and Install
336 Excavator Machine Systems Main Hydraulic Pump - Assemble
336 Excavator Machine Systems Main Hydraulic Pump - Disassemble
336 Excavator Machine Systems Piston Pump (Hydraulic Fan) - Remove and Install
336 Excavator Machine Systems Piston Pump (Hydraulic Fan) - Assemble
336 Excavator Machine Systems Piston Pump (Hydraulic Fan) - Disassemble
794 AC Off-Highway Truck Operator Controls
794 AC Off-Highway Truck Parking
794 AC Off-Highway Truck Additional Messages
C7.1 Commercial Marine Engine Engine Overcrank Occurrence
Reusability Inspection of Certain Planetary Gear Needle Bearings for 797 Transmissions {3030, 3160} Reusability Inspection of Certain Planetary Gear Needle Bearings for 797 Transmissions {3030, 3160}
794 AC Off-Highway Truck Capacities (Refill)
794 AC Off-Highway Truck Lubricant Viscosities - Fluids Recommendations
794 AC Off-Highway Truck Stopping the Engine
794 AC Off-Highway Truck Diesel Exhaust Fluid Filter - Replace - Emission Related Component
320 GC, 320 and 323 Excavator Lubricant Viscosities - Fluids Recommendations
New EMCP 4.2 Software Is Now Used for Certain 3516C and C175-20 Generator Set Engines {1920, 7570, 7620} New EMCP 4.2 Software Is Now Used for Certain 3516C and C175-20 Generator Set Engines {1920, 7570, 7620}
794 AC Off-Highway Truck Diesel Exhaust Fluid - Fill - Emission Related Component
301.5, 301.6, 301.7 CR, 301.8 and 302 CR Mini Hydraulic Excavators Engine Air Filter Service Indicator - Inspect
301.5, 301.6, 301.7 CR, 301.8 and 302 CR Mini Hydraulic Excavators Engine Oil Level - Check
336 Excavator Machine Systems Fuel Tank - Remove and Install
3500 and 3500B Engines Overhaul (Major)
Back to top
The names Caterpillar, John Deere, JD, JCB, Hyundai or any other original equipment manufacturers are registered trademarks of the respective original equipment manufacturers. All names, descriptions, numbers and symbols are used for reference purposes only.
CH-Part.com is in no way associated with any of the manufacturers we have listed. All manufacturer's names and descriptions are for reference only.