Symptoms - SCR Controls

Symptoms - SCR Controls

Important Preliminary Inspections Before Starting

Perform Diagnostic System Check - SCR Controls before using the symptom tables, and verify that all of the following are true:
- The DEF control module and DEF indicator lamp are operating correctly.
- The scan tool data is within the normal operating range. Refer to Scan Tool Data List in this section.
- Verify the customer concern and locate the correct symptom in the table of contents. Inspect the items indicated under that symptom.

Visual and Physical Inspection

Several of the symptom procedures ask for careful visual and physical inspection. This step is extremely important. The visual and physical inspection can lead to correcting a problem without further inspections, and can save valuable time. Ensure that:
- The DEF control module grounds are clean, tight, and in their proper location.
- The exhaust pipes are not collapsed or damaged.
- The SCR system harness wiring and terminals are properly connected and are not pinched or cut.

Intermittent

Inspect for improper installation of electrical components if an intermittent condition exists. Inspect for aftermarket add-on electrical equipment devices, lights, and cellular phones. Verify that no aftermarket equipment is connected to the controller area network (CAN) or other serial data circuit.

The problem may or may not turn ON the DEF indicator lamp or store a DTC. Faulty electrical connections or wiring cause most intermittent problems. Perform a careful visual and physical inspection of the suspect connectors for the following conditions:
- Improperly mated connector halves
- Terminals that are not seated
- Terminals that are damaged or improperly formed

Reform or replace connector terminals in the problem circuit in order to ensure proper contact tension. Remove the terminal from the connector body in order to inspect for poor terminal wire connection.

Road test the vehicle with the DMM connected to the suspected circuit. An abnormal reading that occurs when the malfunction occurs is a good indication that there is a malfunction in the circuit being monitored.

Use the scan tool in order to help detect intermittent conditions. Useful features of the IDSS scan tool include the following:
- Trigger the Snapshot feature in order to capture and store engine parameters when the malfunction occurs. Review this stored information in order to see the specific running conditions that caused the malfunction.
- Freeze Frame/ Failure Record can also aid in locating an intermittent condition. Review and capture the information in the Freeze Frame/ Failure Record associated with the intermittent DTC being diagnosed. To diagnose the SCR control system, the Freeze Frame of the SCR and the Freeze Frame/ Failure Record of the engine are required to be used. Drive the vehicle within the conditions that were present when the DTC originally set.
- Use the Plot Function on the scan tool in order to plot selected data parameters. Review this stored information to aid in locating an intermittent problem. Refer to the scan tool Users Guide for more information.

Use the MIMAMORI ECU in order to help detect intermittent conditions. The MIMAMORI ECU has ability to store engine log data when an event of DTC. Maximum three log data can be stored in the MIMAMORI ECU memory. If more than maximum number of storage is set, oldest log data is overwritten. However, if same DTC is set within eight hours that DTC is not stored in the MIMAMORI ECU memory.

The manual trigger function is to store the log data by an arbitrary operation of the driver when an event of wrong vehicle performance that is instead of an event of DTC. If the driver presses and releases the manual trigger switch once, that time becomes a trigger and one log data before and behind the trigger is stored in the MIMAMORI ECU memory. When there is a space in the MIMAMORI ECU memory, log data is stored in that space. However, when more than maximum number of storage is set, oldest log data is overwritten.

Test for improper installation of electronic equipment such as a light or mobile phone if an intermittent condition exists from the beginning and continues to exist.

Any of the following may cause an intermittent DEF indicator lamp with no stored DTC:
- The DEF control module grounds are loose or dirty. Refer to SCR System Controls Schematics.
- The DEF indicator lamp circuit intermittently shorted to ground.
- Electrical system interference caused by a malfunctioning relay or switch. The electrical component can cause a sharp electrical surge. Normally, the problem will occur when the malfunctioning component is operating.
- There are any open diodes.

The following symptom tables contain groups of possible causes for each symptom. The order of these procedures is not important. If the scan tool readings do not indicate the problems, then proceed in a logical order, easiest to check or most likely to cause first. In order to determine if a specific vehicle is using a particular system or component, refer to SCR System Controls Schematics for an application.

Use the following tables when diagnosing a symptom complaint:
- Intermittent Conditions
- DEF Consumption Too High
- Ammonia Smell Noticeable
- White Crystalline Powder Visible