NO.31 SCR SYSTEM CHECK [MZR-CD 2.2]SM2444567
NO.31 SCR SYSTEM CHECK [MZR-CD 2.2]

id0103f3843400

31

SCR SYSTEM CHECK
DESCRIPTION
• SCR system could not reduce nitrogen oxide
• Ammonia smell from exhaust gas
POSSIBLE CAUSE
• Excessive injection of AdBlue®
― Urea injector malfunction
― Urea pump malfunction
― Urea pressure sensor malfunction
• SCR catalytic deterioration
• Insufficient mixture AdBlue® and exhaust gas
― Urea mixer malfunction (deformed, damaged)
• SCR control unit receive erratic signal from PCM or climate control unit
― Exhaust gas temperature sensor signal malfunction
― MAF sensor signal malfunction
― Ambient temperature sensor signal malfunction
― Communication error between PCM and SCR control unit (HS-CAN for exhaust gas temperature signal, MAF sensor signal)
― Communication error between climate control unit and instrument cluster (MS-CAN for ambient temperature signal)
― Communication error between instrument cluster and SCR control unit (HS-CAN for ambient sensor signal)

Diagnostic Procedure

STEP

INSPECTION

RESULTS

ACTION
1
Retrieve the PCM, climate control unit, instrument cluster and SCR control unit DTCs using the M-MDS.
(See ON-BOARD DIAGNOSTIC TEST [MZR-CD 2.2].)
(See DTC DISPLAY [FULL-AUTO AIR CONDITIONER].)
(See DTC INSPECTION [INSTRUMENT CLUSTER].)
Is there any following DTC displayed?
Yes
Go to the appropriate DTC test.
(See DTC TABLE [MZR-CD 2.2].)
(See DTC TABLE [FULL-AUTO AIR CONDITIONER].)
(See DTC TABLE [INSTRUMENT CLUSTER].)
No
Go to the next step.
2
Visually inspect exhaust system.
Is there any exhaust gas leakage from exhaust system?
Yes
Repair or replace malfunctioning part according to inspection result.
No
Go to the next step.
3
Inspect the urea injector injection amount.
(See SCR SYSTEM INSPECTION [MZR-CD 2.2].)
Is the injection amount normal?
Yes
Go to the next step.
No
Repair or replace malfunctioning part according to inspection result.
4
Remove the urea mixer.
(See EXHAUST SYSTEM REMOVAL/INSTALLATION [MZR-CD 2.2].)
Visually inspect the urea mixer.
Is there any malfunction (deformed, damaged, bent) detected?
Yes
Replace the urea mixer.
No
Go to the next step.
5
Remove the SCR converter.
(See EXHAUST SYSTEM REMOVAL/INSTALLATION [MZR-CD 2.2].)
Visually inspect the SCR converter.
Is there any malfunction (deterioration, deformed, damaged) detected?
Yes
Replace the SCR converter.
No
Troubleshooting is completed.
(The system is normal.)
6
Verify test results.
• If normal, return to the diagnostic index to service any additional symptoms. (See SYMPTOM DIAGNOSTIC INDEX [MZR-CD 2.2].)
• If the malfunction remains, inspect the related Service Information and perform repair or diagnosis.
― If the vehicle is repaired, troubleshooting completed.
― If the vehicle is not repaired or additional diagnostic information is not available, reprogram the PCM if later calibration is available.